Stifle joint

The stifle joint (often simply stifle) is a complex joint in the hind limbs of quadruped mammals such as the sheep, horse or dog. It is the equivalent of the human knee and is often the largest synovial joint in the animal's body. The stifle joint joins three bones: the femur, patella, and tibia. The joint consists of three smaller ones: the femoropatellar joint, medial femorotibial joint, and lateral femorotibial joint.

The stifle joint consists of the femorotibial articulation (femoral and tibial condyles), femoropatellar articulation (femoral trochlea and the patella), and the proximal tibiofibular articulation.

The joint is stabilized by paired collateral ligaments which act to prevent abduction/adduction at the joint, as well as paired cruciate ligaments. The cranial cruciate ligament and the caudal cruciate ligament restrict cranial and caudal translation (respectively) of the tibia on the femur. The cranial cruciate also resists over-extension and inward rotation, and is the most commonly damaged stifle ligament in dogs.

'Cushioning' of the joint is provided by two C-shaped pieces of cartilage called menisci which sit between the medial and lateral chondyles of the distal femur and the tibial plateau. The main biomechanical function of the menisci is probably to divide the joint into two functional units—the 'femoromeniscal joint' for flexion/extension movements and the 'meniscotibial joint' for rotation—a function analogous to that of the disc dividing the temporomandibular (jaw) joint. The menisci also contain nerve endings which are used to assist in proprioreception.

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