Semilunar Cartilages, Coronary And Transverse Ligaments

The semilunar cartilages are used to deepen the joint in the same manner as the cotyloid of the hip and glenoid of the shoulder. It is their method of attachment that is important. The external is nearly circular, the internal is semi-elliptical. The ends are fibrous and are attached in front of and behind the spine of the tibia. The transverse ligament is a band passing across the front from one semilunar cartilage to the other (Fig. 549) As Macalister has pointed out, there is no true coronary ligament. It is the part of the capsular ligament running from the semilunar cartilages to the tibia.

The semilunar cartilages are attached by their outer edges to the capsular ligament. This attachment is less in extent in the case of the external, because its outer surface is obliquely grooved by the tendon of the popliteus muscle, but it has an additional attachment in the ligament of Wrisberg, as stated under the posterior crucial ligament. Humphry("Human Skeleton," 546) has pointed out that the semilunar cartilages in-flexion and extension move with the tibia, but in pronation and supination (rotation) move with the femur.

Ligamenta Alaria And Muco-Sum

Below the patella is a pad of fat extending under the upper portion of the tendo patellae; a bursa is under the lower portion. Passing up from this pad to the intercondyloid notch and crucial ligaments is the ligamen-tum mucosum; below, it is continuous with the synovial fringes at each side of the lower edge of the patella which form the ligamenta alaria. We would suggest that it is possible that these ligaments perform for the knee-joint what Allis has suggested the ligamentum teres does for the hip, viz.: act as a swab to distribute the synovia over the articular surfaces.

Bursae Of The Knee

There are a number of bursae about the knee-joint, but they are not all of importance. Anteriorly there are the prepatellar, suprapatellar, and deep and superficial infrapatellar.

The prepatellar bursa lies in the subcutaneous tissue between the skin and patella. It is often enlarged, constituting "housemaid's knee" (Fig. 550). The bursa is almost always present, but often irregular in shape and character. Injuries frequently cause it to inflame, as do also rheumatoid affections. Sometimes the tendon of the quadriceps over the patella is ossified clear to the surface, which is often irregular and rough, and is felt immediately beneath the skin with apparently no subcutaneous tissue intervening. In these cases the bursa may be very irregular or loculated in shape, or there may be more than one. The sac of the bursa is usually very thin, but becomes thick and distinct as the result of irritation. Excision is usually the quickest way of curing housemaid's knee, but often the easier way of simple incision and drainage with a wick of gauze is sufficient.

The suprapatellar or subfemoral bursa extends from 5 to 7.5 cm. (2 to 3 in.) above the patella beneath the crureus muscle. It is liable to be injured by stabs or punctures, and thereby infect the joint with which it communicates in 8 out of 10 cases. It becomes distended in intra-articular effusions.

Fig. 549.   View of the interior of the knee joint, looking forward.

Fig. 549. - View of the interior of the knee-joint, looking forward.

The infrapatellar bursa are one between the skin and tibial tubercle and the other between the under surface of the tendo patellae and the upper end of the tibia - they are unconnected with the joint and are not often diseased.