An orthopedic brace is provided with an adjustable support assembly having a support arm, a housing and a locking mechanism. The housing includes a travel track which slidably receives the support arm. The locking mechanism includes a lock lever which selectively applies a sufficient force to the support arm to prevent slidable displacement of the support arm in the travel track. The orthopedic brace is further provided with a hinge having a first rotation plate, a second rotation plate, a pivotal connector connecting the first and second rotation plates, a rotation limiting mechanism, and a rotation locking mechanism.