The Bands of the Lateral Meniscus

Abstract

On the basis of examination of 100 mixed preparations of the knee-joint, we have come to the following conclusions:

1. — The posterior surface of the articular capsule is strengthened by the lig. popliteum obliquum and the lig. popliteum arcuatum, the parts of the capsule not strengthened by the bands being situated proximally to and distally from the trairsverse expansion of the oblique popliteal ligament.

(a) The lig. popliteum obliquum is a fasciculus derived from the tendon of the Semimembranosus. From the direction they branch out in, the fibres of the oblique popliteal ligament can conveniently be diviđed into (1) the oblique upward, (2) the transverse and (3) the vertical downward ones, ali of which intersect with the arcuated fibres of the lig. poplitei arcuati, the capsule shovving a thickening at the point of intersection. The oblique upward fibres proceed from the medial side in the direction of the lateral condyle of the femur, laterally delimiting the proximal portion of the capsule in the medial surface of the condyle. The transverse fibres run from the medial to the lateral side to intersect the tendon fibres of the lateral head of the m. gastrocnemius near the lateral condyle of the femur. The vertical dawnward fibres arise from the medial part of the transverse expansion of the oblique popliteal ligament and cross with the arcuated fibres of the arcuate popliteal;

(b) The lig. popliteum arcuatum arises from the lateral epicondyle of the femur and tendon fibres of the lateral head of the m. gastrocnemius, its retinaculum — strengtened by the tendon fibres of the m. popliteus — ending at the capitulum fibulae;

(c) The proximal portion of the capsule not being strenghtened by any of the bands mentioneđ consists, laterally, of the upward and, below, of the transverse fibres of the oblique popliteal ligament. Medially, this portion is delimited by the capsule that covers the medial condyle of the thigh-bone, vvhich is strenghtened by the tendon fibres of the medial head of the m. gastrocnemius. The fibrous layer of the capsule passes upward to the periosteum of the femur;

(d) The distal portion of the capsule, where strengthening bands are equally lacking, is represented, laterally, by hte crossed fibres of the oblique and arcuate popliteal ligaments, above by the transverse prolongation of the oblique popliteal, medially by the initial descending fibres of the lig. popliteum obliguum, and below, the fibrous layer of the capsule passes downward to the periosteum tibiae;

(e) The fat tissue between the fibrous and synovial layers of the capsule is particularly marked below the transverse expansion of the oblique popliteal ligament, and less so around the proximal and distal poitions of the capsule. By its position, the fatty tissue corresponds to corpora adiposa articuli cubiti; its outward appearance, hcwever, is rathei  suggestive of pads of fat associated with the fatty tissue of the popliteal fossa and that investings the cruciate ligaments;

(f) The fibrous layer of the capsule sends off, from the point of intersection of the oblique and arcuate popliteal fibres, fasciculi or sheaves of fibres that proceed in 3 directions to form a kind of fibrous knot situated 1 cm behind the fixed position of the posterior end of the lateral meniscus. One fasciculus passes to the starting point of the lig. menisci lateralis forming a sort of fulcrum for this band. Another fasciculus of fibres passes to the posterior side of the posterior cruciate ligament, and the third part of the capsule is strengthened by the cross-fibres and descends downward, thus laterally delimiting the distal portion of the capsule.

2. The lateral meniscus is in the shape of the letter C, its thickness being 5.2, 7.7, and 6.3 mm in front, laterally and at the posterior end respectively. In front and laterally as far as the lig. collaterale fibulare, it blends completely with the capsule; in the portion of the popliteal groove and bursae m. poplitei, hovvever, it not blends with the capsule. At a distance of 1 cm from the fixed position of its posterior end, the lateral meniscus blend with the capsule which is strengthened up to 1 cm in breadth by the cruciate fibres of the oblique and arcuate popliteal ligaments. In the case of communication betvveen the bursae m. poplitei and the tibiofibular joint, the lateral meniscus blends with the capsule ali around except for the portion of the popliteal groove.

3. The lig. menisci lateralis starts from the posterior part of the lateral meniscus. 1 cm behind the attached position of its posterior end, and passes obliquely, contiguous to the posteror cruciate, to the lateral side of the medial condyle of the femur where it connects. In its initial part, this band receives a fasciculum of fibres from the capsule, the lateral meniscus sending off here fibrous oblique threads to the lateral border of the lig. decussatum posterius as weel as transverse fibres to the anterior side of the posterior cruciate ligament. The lateral meniscus ligament was present in 66 p.c. of our cases, and in 50 p.c. of cases was found together with the Ug. transversum genu. Moreover, with the markedly pronounced menisci twofold bands were also found on its posterior side. Where the lateral meniscus was lacking (34 p.c.) the presence of an anterior prolongation established vvhich we have designated as the lig. menisci lateralis accessorius ventralis; it proceeds, in two hrids of the cases examined, 0.5 cm behind the attached position of the posterior hom of the lateral meniscus and passes along the anterior side of the posterior cruciate joining the fibres of this ligament in its upper course. In one third of the cases this band is completely isolated and passes in front of the posterior cruciate connecting below the attachment of the lig. decussatum posterius at the lateral side of the medial condyle of the thigh-bone.

4. The lig. transversum genu connects the anterior ends of the two menisci; it,s central part looks rather like a ribbon, while the attached parts have the appearance of a triangle. This band sends off from its lateral part fibrous threads which pass into the capsule, thus strengthening the lateral attachment of the lig. transvcrsum genu. It was present and chearly noticeable in 70 p.c. of our cases. The band was lacking in 16 p.c. of the cases; 14 p.c. of the cases showed a lateral prolongation of the lig. transversum genu which is attached to the intercondyloid fossa of the tibia by the major part of its fibres, the rest of the fibres passing into lig. decussatum anterieus.

5. The ligaments of the lateral meniscus function, in our opinion, in the manner of of amplitude regulators of its movements. Since the ligg. decussata establish and ensure the contact vvith articular bodies, and seeing that the menfsci are concerned with the removal of ancongruities of the articular bodies, the conclusion inevitably follovvs that the ligaments regulating the amplitudes of movements of the lateral meniscus must necessarily coact functionally with the cruciate ligaments. Hence it is that we have observed the fact that in cases of extensions, common flexions as well as those of internal and external rotation the lig. transversum genu behaves rather like the anterior part of the lig. decussatum anterius, whereas the lig. menisci lateralis functions in the manner of the posterior end of the posterior cruciate. The lig. menisci lateralis accessorius ventralis, hovvever, behaves in the way of the anterior part of the posterior cruciate. The ligaments proceeding from the capsule towards the lateral meniscus and passing to its posterior end 1 cm behind the attachment of its posterior horn act in the manner of levers reguating and balancing the power of elasticity together with the other bands of the lateral meniscus. It is for this reason also that we have observed the existence of other bands that compensate to some extent the missing ones. Moreover, the functional significance of the ligaments of the lateral meniscus is particularly noteworthy in hyperextensions as well as in rotatory movements in the knee-joint.