How does the knee joint work, and what can cause it to fail? Joint capsule, synovial membrane, synovial fluid.

The knee joint is one of the most complex. The accessibility of the joint to external influences causes frequent trauma to it.

The tibiofibular joint is an independent articulation, and only in 20% of cases, according to some authors, this joint communicates through the bursa mucosa m. poplitei with knee joint.

The articular surface of the femoral condyles is convex, the condyles are separated by a deep intercondylar cavity. The articular surface of the tibial condyles, on the contrary, is slightly concave, with the condyles separated by the intercondylar eminence.

Articular surfaces The femur and tibia are incongruent, but this discrepancy is smoothed out by the cartilaginous formations between them - the menisci. The outer meniscus has the shape of an open circle inside, the inner meniscus is crescent-shaped. The posterior horns of both menisci and the anterior horn of the external meniscus are fixed to the eminentia intercondylaris, the anterior horn of the internal meniscus passes into the lig. transversum genu. Apparently, the latter circumstance has a certain significance in the sense of more frequent traumatization of the internal meniscus.

The articular surfaces are held within the joint cruciate ligaments.

The anterior cruciate ligament is attached to the medial surface of the lateral condyle of the femur and to the anterior intercondylar fossa of the tibia just posterior to the anterior horn of the medial meniscus.

The posterior cruciate ligament is attached to the outer surface of the internal condyle of the femur and to the posterior intercondylar fossa of the tibia, partially to the posterior surface of the latter. A bundle of fibers extends from the posterior cruciate ligament to the posterior part of the external meniscus - lig. menisci lateralis (Roberti).

The cruciate ligaments inhibit hyperextension of the tibia, prevent rotational movements and keep the tibia from moving in the anteroposterior direction; in part, they also prevent excessive flexion of the tibia. When the cruciate ligaments are torn, a drawer sign is noted and sometimes subluxation of the tibia occurs.

Bursa The knee joint consists of two layers - synovial and fibrous. It is attached to the femur above the border of the articular cartilage (0.5-2 cm), on the tibia - slightly below the border of the cartilage. In the anterior section, the capsule is attached to the edge of the articular surface of the patella and fuses with the tendon of the quadriceps femoris muscle.

The epiphyseal zone of the femur (with the exception of the lateral sections) turns out to be located in the cavity of the knee joint, and the epiphyseal line of the tibia lies outside the cavity of the joint.

The fibrous layer of the capsule has unequal thickness throughout and does not have great strength. The capsule is strengthened in front by the tendons of m. quadriceps, laterally - lig. collateralia tibiale and fibulare, behind - lig. popliteum obliquum, lig. popliteum arcuatum.

In addition, the anterior part of the joint capsule is strengthened by the fascia of the knee region, thickened by the tendon fibers of the sartorius muscle and tractus iliotibialis.

The synovial membrane is attached strictly along the edges of the cartilage. In the posterior section it covers the cruciate ligaments, and laterally it passes to the menisci.

Synovial membrane The joint forms a series of folds, turns and bags. There are nine torsions of the knee joint. The largest, unpaired, anterosuperior inversion is located 4-6 cm above the patella, and in the presence of communication with the bursa suprapatellaris - 10-11 cm. Between the inversion and the femur there is a layer of fatty tissue, which allows skeletonizing the bone in this area without opening the joint. However, when in the distal femur (for example, with supracondylar osteotomy, sequestrectomy), this inversion can easily be damaged.

The remaining inversions - anterior lateral, anterioinferior lateral, posterosuperior and posteroinferior (medial and lateral) - are much smaller in size and have less practical significance.

Volvuluses are a place of accumulation of pathological fluid (blood, pus), and, by significantly stretching, they greatly increase the volume of the joint cavity. In the superior and posterolateral inversions, the development of the tuberculous process occurs first when it passes to the joint.

Under normal conditions, the cavity of the knee joint is single, however, with the development of the inflammatory process, the narrow gaps (between the cruciate ligaments and on the sides of the condyles) connecting the anterior and posterior sections of the cavity, due to swelling of the synovial membrane, can close, and the joint cavity is separated into the anterior and posterior sections.

In addition, swelling of the pterygoid folds of the synovial membrane and plica synovialis infrapatellaris during the development of the inflammatory process leads to the division of the anterior part of the knee joint into the inner and outer halves. P. G. Kornev attaches great importance to these folds in the process of delimiting tuberculous inflammation in the joint. Finally, the posterior part of the joint, due to inflammatory swelling of the synovial membrane covering the posterior cruciate ligament, the ligament of the external meniscus, is also divided into separate internal and external sections.

Between the pterygoid folds and the fibrous layer of the knee joint capsule there is a rather large lump of fat, which sometimes undergoes degenerative changes (Hoff's disease). In this case, there are indications for removing the fatty lump.

The joint cavity reaches its greatest capacity with the knee joint slightly bent; in an adult it is 80-100 cm3.

Blood supply The knee joint is carried out by branches of the femoral, popliteal, anterior tibial arteries and the deep femoral artery. There are permanent branches and non-permanent ones. Permanent branches include: a. articulationis genu suprema; upper and lower (paired) arteries of the knee (from a. poplitea); the middle artery of the knee, supplying the cruciate ligaments, as well as the area of ​​the intercondylar fossa of the femur and the intercondylar eminence of the tibia; two recurrent arteries (from the anterior tibial). All these branches form the arterial network of the knee - rete genu. Within this network, individual segments can be distinguished: in the area of ​​the patella, in the area of ​​the femoral condyles.

Innervation The knee joint is carried out by branches of the femoral, obturator, and sciatic nerves.

The main nerve branches of the anterior surface of the knee are located on the inner side of the latter, and the nerve branches of the posterior surface of the joint are located mainly on the outer side.

The common innervation of the hip and knee joints sheds light on the cause of pain in the knee joint in the initial period of tuberculous coxitis. These pains depend on irritation due to inflammatory infiltration of the capsule of the obturator and femoral nerves, which give branches to both the hip and knee.

Movements in the knee joint are more complex. When the tibia flexes, the tibia, in addition to rotating around the transverse axis, performs some posterior sliding along the articular surface of the femoral condyles. This anatomical detail provides a greater range of motion in the knee around its transverse axis (or rather, transverse axes).

Active knee flexion is possible up to an angle of 50°. In addition, passive flexion can be further increased by 30° and hyperextension from the average position can be caused by 10-12°. When the knee is bent, due to relaxation of the lateral ligaments, rotational movements with an amplitude of up to 35-40° are also possible. Finally, with full extension of the knee, a slight so-called final rotation (supination) is observed, depending on the unequal size and shape of the femoral condyles.

The article was prepared and edited by: surgeon

S.P. Mironov, N.A. Eskin, A.K. Orletsky, L.L. Lyalin, D.R. Bogdashevsky.

FGU "CITO named after N.N. Priorov" ROSZDRAVA.
Moscow, Russia.

Introduction

Despite significant progress in instrumental diagnostics, a full clinical examination remains the main method for identifying knee joint pathology. However, the conventionality of clinical and morphological parallels in various injuries and diseases of soft tissues causes significant difficulties in recognizing the nature of the pathological process, as well as in assessing its severity. Therefore, it is not surprising that the proportion of diagnostic errors in this pathology reaches 76-83%.

In connection with the development of modern medical technologies, the diagnostic arsenal has been replenished with a complex of highly informative instrumental methods such as CT, MRI, ultrasound, etc. Each of them has its own advantages and disadvantages. To obtain complete information about soft tissue injuries of the musculoskeletal system (MTOS) required a whole range of techniques, sometimes tedious and expensive, and sometimes unsafe for the patient, especially immediately after injury.

Currently, preference is given to those research methods that, in addition to being highly informative, have such qualities as non-invasiveness, harmlessness, and are also characterized by ease of implementation and interpretation of results, reproducibility and high cost of research. In our opinion, high-resolution ultrasonography in real time meets most of the above requirements, therefore, in the course of our study, we tried to answer the question about the diagnostic effectiveness of ultrasound in determining soft tissue injuries of the musculoskeletal system in orthopedic and trauma patients.

Materials and methods

The total number of patients in the group was 816 people, of which 661 were men (81%), 155 were women (19%), the average age was 43.3±3.9 years.

Patients were admitted to the clinic or examined on an outpatient basis within a period of several hours to 3 weeks from the onset of the disease. 553 (67.8%) people had unilateral lesions, 134 (16.4%) had bilateral lesions. 487 (59.7%) patients in this group were treated surgically, 129 (15.8%) patients were treated conservatively.

All patients, in accordance with the clinical diagnosis, were divided into three subgroups: with meniscal injuries - 465 (56.9%) people; with injuries to the ligamentous apparatus (medial and lateral ligaments) - 269 (32.9%) people; with pathology of the patella and its own ligament - 82 (10.1%) people.

We analyzed the severity of such main nonspecific clinical symptoms as pain, limited mobility of the knee joint and changes in muscle strength (Table 1).

Table 1. Clinical symptoms in patients with injuries and diseases of the knee joint.

Subgroup of patients	Pain in the knee joint		Limitation of joint mobility		Change in muscle strength
	moderate	intense	Yes	No	norm	reduced
Meniscus injury	184	281	281	184	152	128
Ligament damage	175	94	109	160	185	84
Pathology of the patella and its own ligament	53	29	59	23	28	54

The studies were carried out using an HDI-3500 and IU 22 ultrasound scanner (Philips) in real time. As a result of the data obtained, the following main indications for ultrasonography in pathology of the knee joint were identified:

• synovitis;
• damage and inflammation of the ligamentous component and muscles;
• the presence of loose bodies in the joint, cysts;
• damage to the meniscus, cartilage;
• bone pathology;
• tumors and tumor-like diseases.

results

Most often, synovitis occurs in the suprapatellar space (superior inversion). The suprapatellar bursa is the largest in the human body and extends 6 cm upward proximal to the superior pole of the patella. Any impact on the knee joint (traumatic, inflammatory, gouty) leads to the appearance of an increased amount of synovial fluid in the superior inversion of the joint (Fig. 1 a, b).

Rice. 1. Sonograms of synovitis of the knee joint.

A) Severe synovitis of the knee joint with the presence of a thickened synovial membrane with marginal growths (arrow).

b) Prolonged chronic synovitis with the presence of a thickened synovium and areas of sclerosis (arrow).

Friction and gouty bursitis are the most common pathologies. In acute frictional bursitis, the contents of the suprapatellar bursa are usually anechoic. Increased hyperechogenicity of the walls of the bag and contents develops after some time. With gouty bursitis, the content is hypoechoic, sometimes with the presence of hyperechoic inclusions. In the acute stage of the disease, inflammation of the surrounding soft tissues is noted.

Rice. 2. Hemarthrosis in varying degrees of organization.

A)
An excessive amount of effusion of a heterogeneous structure in the form of small hyperechoic inclusions (blood cells) and a hyperechoic strand, indicating a rupture of the synovial membrane.

b)
Organized hematoma with its division into two media. The upper one has a more pronounced organization, the lower one has less organization and the presence of synovial fluid.

Hemorrhagic bursitis is most often observed in athletes as a result of injury. The hemorrhagic contents of the bursa are echogenic with or without the presence of hyperechoic blood clots (Fig. 2). If there is a large amount of hemorrhagic content in the suprapatellar and prepatellar bursa, it is necessary to exclude rupture of the quadriceps tendon (Fig. 3).

Rice. 3. Complete rupture of the quadriceps tendon. Hypoechoic hematoma at the typical location of the tendon. In the fluid formation, a fragment of the tendon is visualized in the form of a “bell tongue” (arrows).

In a conventional gray scale study, a complete quadriceps tendon rupture is defined as complete disruption of the anatomical integrity of the fibers and fibrillar structure of the tendon. The defect is replaced by a hematoma, and effusion appears in the anterior inversion.

With tendonitis, the tendons of the quadriceps femoris muscle thicken at the site of attachment to the patella, and its echogenicity decreases. With chronic tendonitis, microtears, fibrous inclusions in the tendon fibers, and areas of calcification may occur. These changes are combined under the general name - degenerative changes in the tendon (Fig. 4).

Rice. 4. Ossified tendinitis of the quadriceps tendon with the presence of synovitis in the superior inversion. At the site of attachment of the tendon to the upper pole of the patella, ossification with uneven contours is detected (arrow). The tendon is thickened, heterogeneous in structure and hypoechoic in the upper part with the presence of slight synovitis.

H - upper pole of the patella.
B - distal femur.

Prepatellar (Fig. 5) and infrapatellar (Fig. 6 a, b) bursitis is rare, mainly in rheumatoid and infectious arthritis, fractures of the patella, partial damage to the patellar ligament, as well as as a result of the activities of patients (parquet floor workers). Bursitis as a result of long-term use of anticoagulants is quite rare.

Rice. 5.

A) Longitudinal section of prepatellar hemorrhagic bursitis in the first 2 hours after injury. The anechoic contents of the bursitis with the presence of thin hyperechoic inclusions are determined.

b) Longitudinal section of hemorrhagic bursitis 16 hours after injury. In the anechoic contents, more pronounced hyperechoic inclusions are revealed.

Rice. 6.

A) Longitudinal section of the patellar ligament at its attachment to the tibial tuberosity.

When assessing the prepatellar bursa, it is necessary to carry out a sonographic assessment of the contour of the patella (Fig. 7) and the place of attachment of its own and suspensory ligaments (Fig. 8), since as a result of traumatic effects, damage to the periosteum and suspensory ligament occurs, most often the medial one (in case of patellar dislocation). Injuries to the medial collateral ligament are the most common knee injuries.

Rice. 7.

A) With a slight dislocation in the distal direction, the presence of a hematoma at the fracture site (thick arrow) and hemorrhagic prepatellar bursitis (arrow).

b) Fracture of the lower pole of the patella with pronounced dislocation in the distal direction.

In the space between the bone fragments there is a large semi-organized hematoma (arrow); N - patella.

Rice. 8. Longitudinal sonograms of damage to the medial suspensory ligament of the patella and changes in the contour of the patella at its insertion.

The location of the ligament damage (arrows) is determined by its thickening, decreased echogenicity, and disruption of the structuring of the ligament. Under the distal part of the ligament there is a small hematoma in the form of a hypoechoic formation (thin arrow). Detachment of a bone fragment of the patella (curly arrow).

Sonography in diagnosing the pathology of extra-articular ligaments has a high diagnostic value and must be carried out in a longitudinal section, parallel to the long axis of the ligament. When stretched, the ligament thickens and its structure becomes hypoechoic.

In case of partial or complete damage to the ligaments, a violation of its anatomical continuity is determined. The size and extent of damage depends on the type of tear. The hyperechoic structure of the ligament at the site of the rupture becomes hypo- or anechoic, the site of damage is filled with a hematoma, which can be detected as a hypoechoic or anechoic zone with or without hyperechoic inclusions (Fig. 9). Ultrasonographic examination determines the location of the ends of the damaged ligament.

Rice. 9. Complete injury to the medial tibial collateral ligament.

A) rupture of the upper layer of the ligament with filling of the ligament defect with hematoma (arrow) and partial damage in the medial part of the ligament (arrow).

b) complete damage to the ligament at its attachment to the medial femoral condyle.

Thickening at the site of injury and filling with a hypoechoic hematoma with hyperechoic inclusions (arrow);
B - distal femur.

The external fibular collateral ligament is damaged to a lesser extent than the internal one. Ruptures of the external fibular collateral ligament occur with severe internal rotation of the tibia (Fig. 10).

Rice. 10. Longitudinal sonogram of a complete tear of the lateral fibular collateral ligament of the knee with hypoechoic areas (arrow) and small bone fragments (thick arrows) at the insertion of the lateral femoral condyle.

M - head of the fibula.
B - lateral femoral condyle.

Ruptures of the lateral collateral ligaments are often combined with meniscus tears (Fig. 11), and sometimes with damage to the anterior cruciate ligament. According to various authors, ruptures of the cruciate ligaments of the knee joint occur with a frequency of 7.3-62% among all injuries of the capsular ligament apparatus of the knee joint.

Rice. eleven. Complete tear of the medial tibial collateral ligament (arrows) and medial meniscus of the knee joint. A cartilaginous intra-articular body is identified in the interarticular space.

B - distal end of the femur.
T - tibia.

The diagnostic effectiveness of the sonography method in the study of injuries to the anterior and posterior cruciate ligaments depends on the experience of the researcher, the availability of modern ultrasound equipment, knowledge of the clinical signs and anatomy of the knee joint. The most accessible and convenient place for examining the cruciate ligaments is the popliteal fossa. This is the site of attachment of the distal ligaments. The anterior cruciate ligament is attached to the back of the femur, and the posterior cruciate ligament is attached to the back of the tibia.

Both cruciate ligaments appear on sonograms as hypoechoic stripes in a sagittal section. The anterior cruciate ligament is best examined transversely in the popliteal fossa, since full flexion of the knee joint is impossible in acute injury. A comparative study of the contralateral joint is necessary. Complete damage to the ligament is detected as a hypo- or anechoic formation at the site of attachment to the femur. The posterior cruciate ligament can be damaged by severe sprains or a car injury where the knee hits a dashboard. Partial or complete damage is revealed as global thickening of the ligament (Fig. 12 a, b, c).

Rice. 12. Injuries to the cruciate ligament in the popliteal region using a 3.5 MHz transducer.

b) Transverse sonogram. At the site of attachment of the anterior cruciate ligament, a hypoechoic zone is identified (arrow).

V) Damage to the anterior and posterior cruciate ligaments (thin arrows) with separation of a bone fragment (curly arrow), damage to the posterior joint capsule (thick arrow). In the posterior part of the knee joint there are fragments of damaged ligaments floating in a hypoechoic fluid component (hematoma).

B - femur.
T - tibia.
L - lateral femoral condyle.
M - medial femoral condyle.

Ultrasonographic examination must be carried out in two projections: in the transverse - this requires visualization of both femoral condyles - and at an angle of 30° from the longitudinal projection, capturing the lateral part of the medial condyle of the tibia and the medial part of the lateral condyle of the femur in the studied image.

According to the CITO Sports and Ballet Injury Clinic, where mainly athletes are treated, meniscus injuries occupy first place among internal injuries of the knee joint.

The following types of meniscal injuries are distinguished:

• separation of the meniscus from the attachment sites in the area of ​​the posterior and anterior horns and the body of the meniscus in the paracapsular zone;
• ruptures of the posterior and anterior horns and the body of the meniscus in the transchondral zone;
• various combinations of the listed damages;
• excessive mobility of the menisci (rupture of the intermeniscal ligaments, meniscal degeneration);
• chronic trauma and degeneration of the menisci (meniscopathy of a post-traumatic and static nature - varus or valgus knee);
• cystic degeneration of the menisci (mainly external).

Meniscus tears can be complete, incomplete, longitudinal (“watering can handle”), transverse, flap-like, fragmented (Fig. 13 a, b).

Rice. 13. Paracapsular injury of the medial meniscus.

A) Almost complete damage to the meniscus, manifested by a hypoechoic zone (arrow) at the site of attachment of the meniscus to the ligament.

b) Partial damage to the medial ligament (thick arrow) and meniscus (arrows).

In the clinical picture of meniscus damage, acute and chronic periods are distinguished. Diagnosis of meniscal injuries in the acute period is difficult due to the presence of symptoms of reactive nonspecific inflammation, which also occurs with other internal injuries of the joint. Characterized by local pain along the joint space, corresponding to the area of ​​damage (body, anterior, posterior horn), severe limitation of movements, especially extension, the presence of hemarthrosis or effusion. With a single injury, bruises, tears, pinching, and even crushing of the meniscus often occur without tearing it off and separating it from the capsule (Fig. 14 a-d). Predisposing factors for complete rupture of a previously intact meniscus are degenerative phenomena and inflammatory processes in it. With proper conservative treatment of such damage, complete recovery can be achieved (Fig. 15 a-d).

Rice. 14.

A) Complete separation of part of the meniscus (arrow) and its migration into the joint cavity.

b) Transverse tear of the meniscal body (arrow).

The most complete answers to questions on the topic: “superior volvulus of the knee joint fluid.”

Arthritis (synovitis) of the knee joint.
Fluid in the joint cavity is present normally, but in very small quantities. Usually, it is not even detected on ultrasound. Arthritis is inflammation of a joint. On ultrasound you can often find the wording “synovitis”, which in essence is about the same thing. But "arthritis" is a clinical diagnosis. The wording “synovitis” indicates that fluid is found in the joint cavity. There can be many reasons for the appearance of fluid - inflammation, injury, reactive arthritis, cancer, etc.

Fluid in the joint cavity is clearly visible on ultrasound. It accumulates in the upper inversion of the knee joint. As in other organs, the fluid on ultrasound is anechoic (black). A liquid can be homogeneous or inhomogeneous. The fluid may become heterogeneous due to a long-term inflammatory process in the joint cavity. Against the background of anechoic fluid, a thickened synovium can be detected. The synovium produces synovial fluid, which serves to lubricate the joint. But with inflammation, it thickens, sometimes villous growths form on it, which are clearly visible against the background of the liquid. The synovial membrane on ultrasound has increased echogenicity. Its contour is uneven and clear. Based on the amount of fluid, the ultrasound physician can subjectively indicate in the conclusion the severity of synovitis.

Often, fluid descends from the superior inversion to the popliteal region, where it takes on a characteristic appearance (resembles a comma on ultrasound). This formation is called a Baker's cyst. Sometimes loose bodies – bone fragments, calcifications – can be found in the cyst cavity.

Hemarthrosis– presence of blood in the joint cavity. Hemarthrosis occurs due to joint injuries. On ultrasound on the first day after injury, blood has a characteristic appearance. This is a heterogeneous liquid of mixed echogenicity.
Sometimes, clots with increased echogenicity can be detected. In the future, blood on ultrasound can be difficult to distinguish from ordinary fluid. As a rule, it becomes anechoic and homogeneous. And as the hemarthrosis “matures,” the fluid begins to organize, a large number of fibrin fibers appear in it and it becomes heterogeneous, with areas of increased echogenicity. It is impossible to say with certainty about the nature of the fluid in the joint cavity using ultrasound. If the doctor, with the eye of a specialist, suspects that the fluid he removed is blood, then most likely he will write this in the ultrasound report. But the wording “synovitis” in this case will not be considered an error. Because According to ultrasound, synovitis is the presence of fluid in the joint cavity of any nature.

Articulatio genus

Knee-joint form: femoral condyles, tibial condyles and patella. In half of the cases, the lengths of the femoral condyles are equal; in the second half, the length of the external condyle predominates. The medial condyle in all cases is wider and higher than the external one. The articular platforms of the tibia have the following dimensions: at the medial condyle - length 4.1-5.3 cm, width - 2.8-3.8 cm, at the lateral condyle - length 3.3-4.9 cm, width - 3 .0-4.1 cm. The thickness of the cartilaginous cover at the condyles of the femur in the center is 1.6-6 mm, and gradually decreases towards the periphery. The patella has on average: a length of 3.3-5.3 cm, a width of 3.6-5.5 cm and a thickness of 2-2.8 mm.

The articular surface of the femoral condyles is convex, the upper articular surface of the tibia is concave. The congruence of the articular surfaces is increased by cartilaginous menisci. Meniscus lateralis is wider and shorter than the medial meniscus, its shape resembles an incomplete ring, but it can have the form of a disk (1.6%), completely separating the articulating surfaces, or be close in shape (6.5%), having a hole in the center. The meniscus medialis, semilunar in shape, has unequal width, tapering in the middle part. The anterior horns of the meniscus are fixed by the anterior ligaments to the tibia and are connected to each other by lig. transversum genus (occurs from 56 to 73.5% of cases). In addition, medial meniscus using lig. meniscofemorale anterius, which starts from the anterior part of the meniscus and attaches to the inner surface of the lateral condyle in front of the posterior cruciate ligament (occurs from 20.6 to 45.3% of cases). Lateral meniscus with lig. meniscofemorale posterius (occurs from 33.3 to 60% of cases), which starts from the posterior edge of the lateral meniscus behind the posterior cruciate ligament and attaches to the outer surface of the medial condyle of the femur. The inner, thin edge of the meniscus is free, the outer is fused with the joint capsule, with the exception of the posterolateral surface of the lateral meniscus, which is in direct contact with the tendon of the popliteus muscle, covered with a synovial membrane within the recessus subpopliteus. The length of this section is on average 1/5 of the outer circumference of the meniscus.

Rice. 150. Opened knee joint; front view.

The cavity of the knee joint is a complex complex of communicating gaps bounded by articulating bones, menisci, joint capsule, synovial membrane-covered intra-articular ligaments and fatty protrusions. The capacity of the joint cavity in adults with a bent knee ranges from 75 to 150 cm3. The maximum capacity of the joint cavity in men is 150 cm3, in women 130 cm3.

The knee joint capsule has an outer fibrous and inner synovial membrane (layers). The synovial membrane is attached to the edges of the menisci and articular cartilages and, adjoining in certain areas to the femur and tibia, to the inner surface of the fibrous layer of the joint capsule, fatty tissue, intra-articular ligaments and the tendon of the quadriceps femoris muscle, forms protrusions in various places - inversions. The fibrous shell of the capsule on the tibia is attached, slightly moving down from the articular cartilage and reaching the tibial tuberosity in front; it is firmly fixed to the edges of the patella, above which the capsule is attached to the tendon of the quadriceps femoris muscle, then passes well above the articular cartilage to the anterolateral surfaces of the femur, descends along them, bends around the bottom and then behind the epicondyles and is attached above the condyles along the linea intercondylaris.

The knee joint has nine twists: five in the front and four in the back. The protrusion of the synovial membrane, located above the patella and forming the superior patellar inversion, is limited: in front - by the quadriceps femoris muscle, in the back - by the femur, at the top and partially on the sides - by a fold resulting from the transition of the synovial membrane from the posterior surface of the quadriceps femoris muscle to the anterior surface of the femoral muscle bones. According to data, in 90.5% of cases in the arch of the superior inversion there is a larger or smaller hole through which the inversion communicates with the bursa suprapatellaris, and sometimes forms a joint protrusion rising above the patella by 10-12 cm. The length of the upper inversion is 5-8 cm (on average 6.4 cm), width - 3-10 cm.

From above, from the sides and from behind, the upper turn is surrounded by fiber. M. approaches the synovial membrane of the volvulus from above. articularis genus. The inferolateral sections of the superior inversion pass from the medial side into the anterior superior medial inversion, and from the lateral side into the anterior superior lateral inversion. Both last inversions are located on the sides and above the patella, respectively, in front of the anteromedial and anterolateral surfaces of the femoral condyles and behind the fibrous layer of the joint capsule, covered by mm. vastus medialis and lateralis, as well as retinacula patellae mediale and laterale. On the sides of the articular surfaces of the femur, these inversions descend down to the menisci. The gaps between the menisci and the articular surface of the tibia communicate with the lower inversions, and the gaps between the outer surfaces of the condyles and the joint capsule and between the inner surfaces of the condyles and the cruciate ligaments covered with the synovial membrane communicate with the posterior superior inversions. In this case, the medial condyle-capsular fissure is wider than the lateral one. The narrowest part of the condylar-ligamentous gap is located at the intercondylar eminence of the tibia, and the condylar-ligamentous gaps themselves are smaller and shorter than the condylar-capsular ones.

Rice. 151. Articular surfaces, menisci and ligaments of the knee joint in a cross section at the level of the joint space (3/4).
Individually expressed folds protrude into the anterior part of the joint cavity on the sides of the patella - plicae alares, from which or from the apex of the patella to the anterior cruciate ligament the plica synovialis infrapatellaris is directed. These folds of the synovial membrane are formed by a protrusion of adipose tissue - corpus adiposum infrapatellare, which is located below the patella and behind the lig. patellae and the fibrous membrane of the joint capsule, separating the bursa infrapatellaris profunda from the joint cavity.

Rice. 152. Ligaments that strengthen the bursa of the knee joint; back view.

Below the medial and lateral menisci, between the joint capsule and the anterior superomedial and superolateral parts of the tibia, the anterior inferior medial and anterior inferior lateral inversions are located, respectively. At the top, both inversions of the gap between the meniscus and the cartilaginous surface of the tibia communicate with the common cavity of the knee joint. The ends of the inversions facing the midline of the joint are closed and limited in front by the corpus adiposum infrapatellare. The anterior lower medial and lateral inversions each pass on their side into the posterior lower medial and lateral inversions, which, like the anterior ones, are bounded above by the meniscus, in front and on the sides by the tibia, and behind by the joint capsule. The ends of the inversions facing the midline of the joint are closed: at the medial inversion along the inner edge of the posterior cruciate ligament, at the lateral inversion - slightly outward from the lateral edge of the same ligament.

The posterior superior medial and lateral inversions are each located on its own side above the menisci, between the posterior parts of the medial and lateral condyles and the covering parts of the knee joint capsule. The posterior superior inversions, like the inferior ones, do not communicate with each other. They are separated by the fiber of the intercondylar fossa, covered with synovial membrane on the medial and lateral sides. In front, this fiber is adjacent to the cruciate and meniscofemoral ligaments, and behind - to the fibrous membrane of the joint capsule. Adjacent to the posterior superior and inferior lateral inversions is the popliteus tendon, which here is covered in front and on the sides with a synovial membrane, forming the recessus subpopliteus. This pocket, through larger or smaller openings, can communicate with the posterior superior and inferior lateral inversions, as a result of which both inversions communicate with each other by a canal, which occurs in 85% of cases. In other cases, this canal is closed and is represented by a protrusion from the side of the posterior superior lateral inversion. The lower end of the recessus subpopliteus in 88% of cases is directly adjacent to the posterior surface of the articulatio tibiofibularis, and in 18.5% of cases it communicates with it, connecting the cavities of the knee and tibial and fibular joints. Of great practical importance (penetration of pus when driven outside the joint, the occurrence of para-articular phlegmon) are the connections between the cavity of the knee joint and the synovial bursae of the muscles, which are weak points of the capsule of the knee joint. According to the observations of V. M. Ambardzhanyan, such communications occur between the posterior superior medial inversion of the knee joint and the bursa subtendinea m. gastrocnemii medialis (80%) or bursa m. semimembranosi (10%) and between the posterior superior lateral inversion and bursa subtendinea m. gastrocnemii lateralis (24%). The weak points of the knee joint capsule also include the recessus subpopliteus and the superior patellar inversion. Breaking through weak spots, pus can form anterior deep swellings of the thigh in the form of inter- and subfascial phlegmons under the heads of m. quadriceps femoris. With popliteal swelling, pus from the popliteal fossa can spread to both the thigh and lower leg. The capsule of the knee joint is strengthened by the tendons of the adjacent muscles, internal and external ligaments. In addition to the meniscofemoral ligaments described above, the cruciate ligaments of the knee are located between the synovial and fibrous membranes of the joint. Lig. The cruciatum anterius begins from the posterior part of the inner surface of the lateral condyle of the femur, goes down, forward and medially and is attached to the posterior part of the area intercondylaris anterior and to the anterior part of the tuberculum intercondylare mediale of the tibia.

Rice. 153. Opened knee joint; back view.
The length of the ligament along the medial edge is 3.3 cm, along the lateral edge - 2.6 cm. Lig. The cruciatum posterius starts from the outer surface of the medial femoral condyle, goes down and slightly back and, crossing with the anterior cruciate ligament, attaches to the area intercondylaris posterior and to the posterior edge of the upper articular surface of the tibia. The length of the ligament along the lateral edge is 3.9 cm, along the medial edge - 2.9 cm.

Rice. 154. Opened knee joint; view from the medial side.

Rice. 155. Opened knee joint; view from the lateral side.

The joint is strengthened in front by lig. patellae, running from the patella to the tibial tuberosity. In front and medially - retinaculum patellae mediale, consisting of transverse fibers running from the medial epicondyle to the patella, and longitudinal fibers. The retinaculum patellae laterale is located anteriorly and laterally, the transverse fibers of which go from the lateral epicondyle to the patella, and the longitudinal fibers from the patella to the anterolateral edge of the tibia and to the tractus iliotibialis. On the lateral side the joint is strengthened by lig. collateral fibulare. The fibular collateral ligament originates from the lateral epicondyle of the femur and is attached to the head of the fibula in the form of a flat-rounded cord. The length of the ligament is 4-7 cm, thickness - 2-8 cm. The ligament runs isolated from the articular capsule. Below, at the head of the fibula, it is covered by a sheath or simply adjacent to it behind or outside the tendon of the biceps femoris muscle. On the medial side, the capsule of the knee joint is strengthened by lig. collateral tibiale. It starts from the medial epicondyle of the femur and attaches to the medial surface of the tibia. The length of the ligament is 7.1-12.5 cm, width - 5-15 mm. In almost half of the cases, the ligament has the appearance of a wide limited strip, sometimes (22%) only the anterior part of the ligament is developed, sometimes (13%) the entire ligament is insufficiently developed. At the back, the articular bursa of the knee joint is strengthened by the oblique popliteal ligament, which is isolated from the outside but intimately connected to the bursa. Lig. popliteum obliquum runs from the posteromedial edge of the tibia to the lateral condyle of the femur; most often well expressed. The ligament is a continuation of the lateral bundle of the semimembranosus tendon. Another ligament is lig. popliteum arcuatum - arcuately covers the posterior superolateral part of the popliteus muscle and is part of its fibrous sheath. The knee joint is spherical in shape, and block-rotatory in function.

Rice. 156. Sagittal section of the knee joint.

The blood supply to the knee joint comes from the rete articulare genus. From the arterial network of the knee joint, networks of the synovial membrane are formed, located in the subsynovial layer and in the thickness of the synovial membrane. The menisci are supplied with blood vessels from the adjacent sections of the synovial membrane, from the middle and lower medial and lateral arteries of the knee. The cruciate ligaments are supplied with blood by the middle artery of the knee, which near the ligaments is divided into ascending and descending branches that supply not only the ligaments, but also the epiphyses of the femur and tibia, tissue, synovial membrane, and menisci. The descending branch of the anterior cruciate ligament forms a permanent anastomosis with branches penetrating the plica synovialis infrapatellaris from the inferior arteries of the knee and the anterior tibial recurrent artery.

Rice. 157. Frontal cut of the knee joint.

Veins from all parts of the knee joint originate from capillary networks. Small veins run independently of the arteries, while large veins accompany the arteries one or two at a time. The small veins of the condyles of the femur are united into a single plexus, from which larger veins are formed that extend to the surface of the bone along the lateral surfaces of the condyles above the facies patellaris, in the area of ​​the intercondylar fossa and in the lower part of the popliteal surface. In the condyles of the tibia, the intraosseous veins are located in the frontal plane perpendicular to the long axis of the diaphysis and with 8-10 trunks they reach the surface of the bone in the area of ​​the lateral surfaces of the condyles.

Lymph from the knee joint flows through lymphatic vessels that accompany the blood vessels. From the superomedial part of the bursa of the knee joint, lymphatic vessels along the course of a. genus descendens and a. femoralis go to the deep inguinal lymph nodes. From the area of ​​branching of the superior and inferior medial and lateral arteries of the knee and the anterior tibial recurrent artery, lymph flows into the popliteal lymph nodes. From the posterior sections of the joint capsule, from the cruciate ligaments, lymph flows into a lymph node located on the capsule, most often near a. genus media.

Numerous branches of the femoral, obturator and sciatic nerves approach the knee joint. The capsule and ligaments of the anterior surface of the joint are innervated by: I) in the area of ​​the medial quadrants - branches from rr. cutanei anteriores and the musculocutaneous branch of the femoral nerve (sometimes very large - from 0.47 to 1.2 mm in diameter), descending down m. vastus medialis and dividing into 3-5 branches. Sometimes smaller branches from this branch penetrate into the anterior inferolateral quadrant; 2) stems of the muscular branch innervating m. vastus medialis; 3) g. infrapatellaris from n. saphenus innervates the inferomedial and inferolateral quadrants of the joint capsule. The branches of M. infrapatellaris can also penetrate into the upper quadrants of the capsule. Branches of the obturator nerve, which are part of n. saphenus, innervate more often the superomedial and less often the superolateral quadrants of the capsule; 4) the capsule and ligaments of the superior lateral quadrant are innervated by branches from the muscular branch to m. vastus lateralis from the femoral nerve and a branch of the sciatic nerve emerging from under the biceps femoris muscle above the lateral epicondyle of the femur; 5) the inferolateral quadrant of the anterior surface of the joint is also innervated by the branches of n. peroneus communis, extending in the region of the head of the fibula, and the branches of n. peroneus profundus, accompanying the branches of a. recurrens tibialis anterior.

The posterior surface of the joint capsule is innervated by: 1) lateral quadrants - branches of the sciatic nerve, extending 6-8 cm above the level of division of the sciatic nerve with its low division, and from the tibial nerve - with high division. The branches are located lateral to the vascular bundle. From the common peroneal nerve in the region of the head of the fibula, branches begin that return back and innervate the joint capsule in its lower parts. Branches to the joint can also extend from muscle branches to the short head of the biceps femoris muscle; 2) the medial quadrants of the capsule are innervated by the branches of the tibial nerve and the posterior branch of the obturator nerve, emerging from the adductor magnus muscle and reaching the joint capsule along its posterior surface.

The most developed intraorgan nervous apparatus is found in the retinaculum patellae mediale, lig. collaterale tibiale and in the area of ​​the medial surface of the knee joint capsule. In the fibrous and synovial membranes of the capsule there is a single nerve plexus. Nerves enter the menisci from the side of the synovium and, to a lesser extent, from the side of the cruciate ligaments. In ligaments, nerve elements are localized mainly in the peritenonium and endotenonium. The interconnected nerves of the ligaments, menisci and capsule form the complete nervous system of the knee joint.

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The knee joint, along with the hip joint, is the largest and most powerful joint in the human skeleton. It unites the bones of the thigh and lower leg, which provide range of motion when walking. The joint has a complex complex structure, in which each element ensures the functioning of the knee in particular and the ability to walk in general.

The structure of the human knee joint explains the cause of emerging pathologies and helps to understand the etiology and course of inflammatory and degenerative diseases. Even small deviations from the norm in any element of the joint can cause pain and limited mobility.

Anatomy

Three bones of the knee joint are involved in the formation of the joint: the femur, tibia and patella. Inside the joint, on the tibial plateau, are located that increase the stability of the structure and ensure rational distribution of the load. During movement, the menisci spring - they compress and unclench, ensuring a smooth gait and protecting the articulation elements from abrasion. Despite their small size, the importance of the menisci is very great - when they are destroyed, the stability of the knee decreases and arthrosis inevitably occurs.

In addition to bones and menisci, the constituent elements of the articulation are the articular capsule, which forms the inversions of the knee joint and the synovial bursae, and ligaments. The ligaments that form the knee joint are formed by connective tissue. They fix bones, strengthen joints and limit range of motion. Ligaments provide stability to the joint and prevent movement of its structures. When injuries occur, ligaments are sprained or torn.

The knee is innervated by the popliteal nerve. It is located behind the joint and is part of the sciatic nerve that passes to the foot and leg. The sciatic nerve provides sensation and movement to the leg. The popliteal artery and vein are responsible for the blood supply, repeating the course of the nerve branches.

Structure of the knee joint

The main joint-forming elements are considered to be the following:

• femoral condyles
• tibial plateau
• knee cap
• menisci
• joint capsule
• ligaments

The knee joint itself is formed by the heads of the femur and tibia. The head of the tibia is almost flat with a slight depression, and it is called a plateau, in which there is a medial part, located in the midline of the body, and a lateral part.

The head of the femur consists of two large rounded spherical protrusions, each of which is called the condyle of the knee joint. The condyle of the knee joint located on the inside is called medial (internal), and the opposite one is called lateral (external). The articular heads do not match in shape, and their congruence (correspondence) is achieved due to two menisci - medial and lateral, respectively.

The articular cavity is a gap that is limited by the heads of the bones, menisci and capsule walls. Inside the cavity there is synovial fluid, which ensures optimal gliding during movement, reduces friction of the articular cartilages and nourishes them. The surfaces of the bones entering the articulation are covered with cartilage tissue.

Hyaline cartilage of the knee joint is white, shiny, dense, 4-5 mm thick. Its purpose is to reduce friction between articular surfaces during movement. Healthy knee joint cartilage has a perfectly smooth surface. Various diseases (arthritis, arthrosis, gout, etc.) lead to damage to the surface of hyaline cartilage, which, in turn, causes pain when walking and limited range of motion.

Knee cap

The sesamoid bone, or patella, covers the front of the knee joint and protects it from injury. It is located in the tendons of the quadriceps muscle, has no fixation, is mobile and can move in all directions. The upper part of the patella has a rounded shape and is called the base, the elongated lower part is called the apex. On the inside of the knee is the pes anserine - the junction of the tendons of the 3 muscles.

Joint capsule

The bursa of the knee joint is a fibrous sheath that limits the outside of the articular cavity. It is attached to the tibia and femur bones. The capsule has low tension, which ensures a large range of motion in the knee in different planes. The joint capsule nourishes the articulation elements, protects them from external influences and wear. The posterior section of the capsule, located on the inside of the knee, is thicker and resembles a sieve - blood vessels pass through numerous holes, and blood supply to the joint is ensured.

The capsule of the knee joint has two membranes: internal synovial and external fibrous. The dense fibrous membrane performs protective functions. It has a simple structure and is firmly fixed. The synovial membrane produces a fluid that is appropriately named. It is covered with small outgrowths - villi, which increase its surface area.

In places of contact with the bones of the articulation, the synovial membrane forms a small protrusion - inversion of the knee joint. In total, there are 13 inversions, which are classified depending on their location: medial, lateral, anterior, inferior, superior inversion. They increase the cavity of the joint, and in pathological processes they serve as places for the accumulation of exudate, pus and blood.

Knee joint bags

They are an important addition, thanks to which muscles and tendons can move freely and painlessly. There are six main bags, which look like small slit-like cavities formed by the tissue of the synovial membrane. Inside they contain synovial fluid and can communicate with the articulation cavity or not. Bags begin to form after a person is born, under the influence of loads in the area of ​​the knee joint. With age, their number and volume increase.

Biomechanics of the knee

The knee joint provides support for the entire skeleton, bears the weight of the human body and experiences the greatest load when walking and moving. It performs many different movements, and therefore has complex biomechanics. The knee is capable of flexion, extension and circular rotational movements. The complex anatomy of the human knee joint ensures its wide functionality, coordinated work of all elements, optimal mobility and shock absorption.

Pathologies of the knee joint

Pathological changes in the musculoskeletal system can be caused by congenital pathology, injuries and diseases. The main signs indicating the presence of violations are:

• inflammatory process;
• painful sensations;
• limitation of mobility.

The degree of damage to the elements of the articulation, coupled with the cause of their occurrence, determines the localization and intensity of the pain syndrome. Pain can be diagnosed periodically, be constant, appear when trying to bend/extend the knee, or be a consequence of physical activity. One of the consequences of ongoing inflammatory and degenerative processes is deformation of the knee joint, leading to serious illnesses including disability.

Anomalies of the development of the knee joint

There is valgus and varus deformity of the knee joints, which can be congenital or acquired. The diagnosis is made using an x-ray. Normally, the legs of a standing person are straight and parallel to each other. With valgus deformity of the knee joint, they are curved - on the outside, an open angle appears in the knee area between the lower leg and the thigh.

The deformity may affect one or two knees. With bilateral curvature, the legs resemble the letter “X” in shape. Varus deformity of the knee joints bends the bones in the opposite direction and the shape of the legs resembles the letter “O”. With this pathology, the knee joint develops unevenly: the joint space decreases on the inside and widens on the outside. Then the changes affect the ligaments: the outer ones stretch, and the inner ones atrophy.

Each type of curvature is a complex pathology that requires complex treatment. If left untreated, the risk of excessive knee mobility, habitual dislocations, severe contractures, ankylosis and spinal pathologies is quite high.

Valgus and varus deformity in adults

It is an acquired pathology and most often appears with deforming arthrosis. In this case, the cartilage tissue of the joint undergoes destruction and irreversible changes, leading to loss of mobility of the knee. Also, deformation can be a consequence of injuries and inflammatory-degenerative diseases that cause changes in the structure of bones, muscles and tendons:

• compound fracture with displacement;
• ligament rupture;
• habitual knee dislocation;
• immune and endocrine diseases;
• arthritis and arthrosis.

In adults, treatment of a deformed knee joint is inextricably linked to the underlying cause and is symptomatic. Therapy includes the following points:

1. painkillers;
2. NSAIDs - non-steroidal anti-inflammatory drugs;
3. glucocorticosteroids;
4. vasoregulating drugs and venotonics;
5. chondroprotectors;
6. physiotherapeutic treatment;
7. massage.

Drug treatment is aimed at eliminating pain, restoring cartilage, improving metabolism and tissue nutrition, and maintaining joint mobility.

Valgus and varus deformity in children

Acquired varus or valgus deformity of the knee joints in children, which appears by 10-18 months, is associated with deviations in the formation of the child’s musculoskeletal system. As a rule, the deformity is diagnosed in weakened children with muscle hypotonia. It appears as a result of stress on the legs against the background of a weak muscular-ligamentous system. The cause of such a deviation may be prematurity of the child, intrauterine malnutrition, congenital weakness of connective tissue, general weakness of the body, or previous rickets.

The cause of the secondary pathology that causes abnormalities in the formation of the knee joint is neuromuscular diseases: polyneuropathy, cerebral palsy, muscular dystrophy, poliomyelitis. Deformation of the joint not only causes curvature of the legs, but also has an extremely detrimental effect on the entire body.

Quite often the feet and hip joints suffer, and with age, flat feet and coxarthrosis develop.

Treatment of hallux valgus and varus deformity in children includes:

• load limitation;
• wearing orthopedic shoes;
• use of orthoses and splints;
• massage;
• physiotherapy, most often paraffin wraps;
• physical therapy classes.

Conclusion

Having a complex structure, the knee joint bears a large load and performs many functions. It is a direct participant in walking and affects the quality of life. Paying attention to your body and taking care of the health of all its constituent elements will help you avoid knee pain and maintain an active lifestyle for a long time.