Knee Joint (Left)

Description

The knee joint is the largest joint in the body. It consists of three articulations, two femorotibial articulations between the femoral and the tibial condyles, and one intermediate patellofemoral articulation between the patella and the femur. The articulating surfaces are covered over by hyaline cartilage. It should be noted that the fibula does not contribute to the knee joint.

The knee joint is a hinge variety of synovial joint, bringing about movements such as flexion and extension. In addition, rotatory movements occur on the knee joint. For instance, medial rotation of the femur occurs in full extension (locking of knee joint), while lateral rotation (unlocking) occurs due to contraction of popliteus muscle, prior to bringing about flexion at the knee joint.

The fibrous capsule of the knee joint encloses the articulating surfaces and is lined on its inner surface by a synovial membrane. In certain places, the synovial membrane protrudes from the capsule to form extracapsular fluid-filled sacs called bursae. The bursae function as gliding surfaces to reduce friction between moving tissues of the body, such as between tendon and bone, ligament and bone, tendons and ligaments, and between muscles.

Ligaments of the knee joint include collateral and patellar ligaments and the cruciate ligaments. The collateral ligaments are extracapsular and reinforce the fibrous capsule. The patellar ligament also lies outside the capsule and is a continuation of the quadriceps tendon, which attaches to the tibial tuberosity. The anterior and posterior cruciate ligaments are intracapsular and prevent posterior and anterior dislocation of the femur on the tibia, respectively.