Knee knee is a modified hinge joint, a type of synovial joint, which is composed of three functional compartments: the patellofemoral articulation, consisting of the patella, or "kneecap", and the patellar groove on the front of the femur through which it slides; and the medial and lateral tibiofemoral articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg. The joint is bathed in synovial fluid which is contained inside the synovial membrane called the joint capsule. The posterolateral corner of the knee is an area that has recently been the subject of renewed scrutiny
Vertical clinging and leaping phalangeal index, low intermembral index, femurs with cylindrical head and high, narrow patellar grooves, and fused fibula and tibia. The high phalangeal index is the elongation of the phalangeal finger bones, which helps vertical clingers who require increased prehensile power in their hands to support their large bulk. The low intermebral index is the total length of the humerus and radius in percentage of total length of the femur and tibia. The features of the femur is part of an evolution of elongated femurs that helps the primates' extreme range of flexion and extension, which allows them to perform their