Range of Motion (ROM) and Gait Function

The primary motions of the normal knee joint are extension and flexion, and the passive ROM is approximately 0–160°. Active extension ROM is 0°. In contrast, the flexion ROM is affected by the hip joint position and is 140° in hip flexion and 120° in hip extension because the medial and lateral hamstrings, which are the agonist muscles of knee flexion, are biarticular muscles. Osteoarthritis of the knee causes various degrees of ROM limitation depending on the degree of progression, which leads to difficulties in carrying out daily activities (Table 67.1) [1]. Factors that cause ROM limitation include pain, knee joint effusion, periarticular muscle tightness, osteophyte formation, and ligament and joint capsule degeneration.