Orthopedics - Oleksa A.P. 2006

Congenital and acquired deformities of the lower extremity
Congenital defects of the knee joint
Meniscal developmental anomalies

The menisci of the knee joint are vital anatomical and functional structures. They ensure congruence and proper alignment between the differently shaped articular surfaces of the Femur and Tibia, evenly distribute the load of the bone processes during movement, reduce friction, and stabilize the knee joint alongside the ligamentous apparatus. Notably, the menisci also act as Shock absorbers and braking elements, preventing excessive mobility of the knee joint in the sagittal plane.

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Fig. 173. Flexed knees resulting from spastic paralysis.

According to embryologists, the femur and tibia begin to form as early as the 40th–45th day of gestation. They appear as embryonic Cartilage tissue separated by a cleft filled with mesenchymal tissue, from which the menisci develop. During this period, three distinct zones can be identified within this blastemal mesenchymal disc: upper and lower zones (which later form the femoral and tibial processes) and an intermediate zone (from which the synovial membrane and menisci develop).

This mesenchymal disc varies in thickness—thinner in the center and thicker at the edges—and the joint cavity is not yet formed.

By the 56th–58th day of gestation, the embryo's menisci are already well-defined as triangular structures, and by the 70th–72nd day, The Structure of the knee joint is largely formed. The femur and tibia undergo chondrification, and the Patella and ligamentous apparatus appear. Over the next 10 days, the knee joint cavity forms. Thus, by the end of the twelfth week of gestation, all Structural elements of the knee joint are established (with the menisci acquiring a crescent shape as they develop), featuring excellent Blood supply across all areas, an increasing density of Collagen fibers near their attachment sites, and radial fibers along the tibial surface.

In the postnatal period, the menisci and ligaments grow and develop in tandem with the bone processes. Their cellularity decreases while the proportion of fibrous fibers increases; the blood supply on the inner side gradually diminishes until vessels disappear entirely, after which these Regions of the menisci are nourished by synovial fluid. By the age of 12, a child's menisci reach their mature shape, which essentially remains unchanged throughout life.

However, anomalies in meniscus morphogenesis have been recognized for over a century. As early as 1889, R. B. Young described a meniscus that was disc-shaped rather than crescentic. Subsequently, discoid menisci were documented by R. Fick (1904), A. G. Fisher (1924), M. Langer (1928), and D. Dunkan (1932), as well as reported as casuistic cases by several other authors. Meniscal pathology in children and adolescents was also highlighted by B. I. Simenach (1977).

E. F. Samoylovich, O. K. Shaklichev, and Y. Y. Serafin (1993) identified Developmental anomalies of the menisci, ligaments, and their attachments to the Joint Capsule and bones in 109 children (3.49% of all knee injuries and conditions they treated). This cohort was clinically diverse, as such anomalies and malformations are highly variable and present numerous transitional forms.

O. F. Snellman and R. H. Stenstrom distinguish five MAIN TYPES OF discoid meniscus, as illustrated in Fig. 174.

Anomalous menisci may present a round-oval shape, occasionally with a central perforation—this is the primitive type. The intermediate type features a disc that is pathologically altered on one side. The infantile type occurs when the horns of the meniscus retain normal shape and dimensions while the body is broadened and thickened. An enlarged anterior horn (megacornu anterius) constitutes the fourth type, and an enlarged posterior horn (megacornu posterior) represents the fifth type.

Some orthopedists describe an inconstant meniscocapsular sulcus—a shallow, gentle groove between the superior surface of the meniscus and the joint capsule—whereas others note it as deep and slit-like, particularly in the region of the posterior horn of the lateral meniscus. In such cases, the meniscus is anchored to the capsule only by a thin duplication of the synovial membrane.

Occasionally, surgery reveals an abnormal attachment of the transverse ligament of the knee, which normally connects and stabilizes the anterior horns of the menisci. When malformed, it typically fails to connect with the edge of the tibia, leading to herniation of Hoffa's fat pads. There are also instances where discoid menisci are associated with anomalous attachments of the cruciate ligaments. Such anomalies may occur in older children in either one or both knees, and are more frequently observed in the lateral meniscus, although bilateral discoid menisci have also been documented (G. P. Rieumau, L. Ficat, 1954; E. A. Riachi, 1963; P. A. Nathan, S. C. Cole, 1969; and others).

S. Y. Doletsky (1983) considers The Emergence of meniscal pathology to be a congenital embryopathy that develops between the 6th and 12th weeks of fetal life. As the embryo and subsequent fetus grow and develop, a gradual mutual adaptation of the articular ends and the Ligamentous apparatus of the knee joint takes place. These adaptive mechanisms can compensate for a long time for any anatomical discrepancies in joint components during function. Consequently, in some children, abnormal meniscus Morphology may remain clinically silent and is only discovered incidentally during knee surgeries performed for other reasons. Decompensation typically occurs only when the child finishes GROWTH AND DEVELOPMENT, at which point Clinical symptoms of joint pathology may manifest.

Fig. 174. Variants of discoid meniscus shapes (R. H. Stenstrom).

Literature data indicate that the leading symptom of a discoid meniscus is the "snapping knee" phenomenon (*schnappendes knie*), first described by Lannelongue and later investigated by F. Kroiss in 1910. The snapping sound is caused by the femoral condyle sliding over the thickened portion of the meniscus during knee flexion and extension. However, this snapping does not occur when the thickening is confined to the anterior or posterior horn. In such cases, patients may experience limited extension or flexion of the leg at the knee joint, intermittent locking, occasional mild Muscle atrophy, or even recurrent synovitis.

Patients sometimes complain of joint pain following physical overload or sudden knee movements. Sharp pain resolves quickly, but protective muscle guarding and restricted joint mobility may persist for some time. Palpation can occasionally reveal tenderness over the PROJECTION OF THE discoid meniscus.

Thus, the presence of these signs of a discoid meniscus warrants further knee evaluation. Standard radiography of the knee joint in three projections does not always confirm the clinical Diagnosis of a discoid meniscus.

Contrast arthrography (Tarkhanov's method) involving the injection of contrast agents into the joint is a more informative diagnostic Procedure; however, even this method—particularly pneumoarthrography—yields inaccurate results in nearly half of patients.

Today, sonography is most commonly used for diagnosis, allowing the joint to be examined in multiple planes to detect pathological changes within the meniscus, though it may complicate or even preclude the visualization of other structural knee abnormalities.

Diagnostic arthroscopy remains the most informative method and can simultaneously serve a therapeutic purpose, allowing pathologically altered areas of the meniscus to be resected and removed. Furthermore, it provides visualization of nearly 75% of all intra-articular structures of the knee, which, when combined with prior clinical and radiological data, helps clarify the knee pathology.

Opinions vary regarding the management of congenital knee meniscus pathology. R. McAusland suggests that if a child has no functional Impairment of the knee joint, surgery is unnecessary. Other orthopedists argue that even in the presence of mild knee instability, children under six should not undergo surgery, as spontaneous resolution can occur.

As noted earlier, congenital discoid meniscus manifests clinically in older children during the decompensation phase. Therefore, once the diagnosis is confirmed, surgical intervention is indicated to prevent impaired joint function, instability, pain, synovitis, articular surface incongruity, and The Development of osteoarthritis.

The Use of arthroscopic techniques in orthopedic surgery allows for minimally invasive partial resection or removal of the pathological meniscus, thereby preventing potential complications. Notably, the young patient's body possesses a remarkable capacity to restore the integrity of the resected meniscus and the function of the knee joint.

Fabella of the Knee Region

The fabella is a round or oval sesamoid bone identified radiologically at the level of the popliteal fossa. The name originates from the Latin word "fabella", meaning "little bean". It is present in approximately 20% of individuals examined (M.V. Volkov, 1968).

Located within the tendon of the lateral HEAD of the gastrocnemius muscle (note: adapting to standard Anatomical Terminology while keeping the Translation natural; or staying true to the source: the tendon of the lateral head of the quadriceps muscle), the fabella is clinically asymptomatic and is typically discovered incidentally on radiographs.

Volkov points out that trauma to the bone may lead to pain. In such cases, patients should be prescribed thermal treatments and temporary limb immobilization. As for surgery, difficulties often arise during its excision without significant damage to the tendon.