The ventral capsule is attached to the borders of the articular surfaces of the femur and tibia on their ventral sides, to the menisci, and to the epicondyles of the femur and the tuberosities of the tibia. Its walls are stronger and its cavity smaller than those of the dorsal capsule.
The ligaments of the knee-joint (Figs. 60 and 61), aside from the capsules, may be classified into: (1) those which are connected with the patella; (2) =collateral= ligaments (Fig. 60, _i_ and _j_), which pass from the epicondyles directly distad along the sides of the joint to the tibia or fibula; (3) =crucial= ligaments (Fig. 60, _g_ and _h_; Fig. 61, _c_ and _d_), which cross within the joint from one side of the femur to the opposite side of the tibia; (4) ligaments which hold the menisci in place (Fig. 60, _e_ and _f_; Fig. 61, _e_ and _f_).
(1) LIGAMENTS OF THE PATELLA.--The patella is imbedded in the dorsal wall of the dorsal capsule of the joint. From its distal end a strong tendon or ligament passes distad to the crest of the tibia. This is known as the =ligamentum patellæ=: it may be considered a part of the tendon of M. quadriceps femoris. On the lateral side the capsule of the joint is strengthened by the transverse fibres of the tendon of M. plantaris, which aid in holding the patella in place.
(2) COLLATERAL LIGAMENTS.--Of these there are two. The =ligamentum collaterale fibulare= (Fig. 60, _j_) is attached to the lateral epicondyle of the femur and passes distad across the tendon of the plantaris muscle to the head of the fibula. Dorsad of the fibular ligament and parallel with it passes the tendon of origin of the extensor longus digitorum. The =ligamentum collaterale tibiale= (Fig. 60, _i_; Fig. 61, _g_) begins on the medial epicondyle of the femur and passes distad to the lateral tuberosity of the tibia; part of it passes one to one and a half centimeters distad of the tuberosity to be attached to a rough ridge on the side of the tibia.
[Illustration: FIG. 60.--KNEE-JOINT, FROM THE DORSAL OR PATELLAR SIDE.
FIG. 61.--KNEE-JOINT, FROM THE VENTRAL OR FLEXOR SIDE.
Fig. 60.--The patella has been removed. 1, femur; 2, tibia; 3, fibula. _a_, patellar surface of femur; _b_, tubercle for attachment of ligamentum patellæ; _c_, medial meniscus; _d_, lateral meniscus; _e_, _f_, ligaments of the menisci; _g_, ligamentum cruciatum anterius; _h_, ligamentum cruciatum posterius; _i_, ligamentum collaterale tibiale; _j_, ligamentum collaterale fibulare.