The knee is made up of four bones that interact in two joints: the tibiofemoral and patellofemoral joints. These joints allow flexion/extension, rotation, and translation while providing load transfer. The knee flexes from 0-135 degrees, and the femoral condyles translate posteriorly during flexion. The tibia externally rotates in extension and internally rotates in flexion, locking the knee. Larger Q angles increase risk of lateral patellar subluxation. Forces through the knee increase with activity from 0.3 times body weight while walking to 7 times body weight while squatting.