Three sets of muscles in the upper leg all attached to the knee joint. As mentioned above, pectineus, satorius and quadriceps are in anterior group; hamstring muscles are in posterior group; adductor magnus, adductor longus and adductor brevis and gracilis are in medial group. Tensor fasciae continuing with iliotibial tract are in the lateral side. Inflamed iliotibial band is one common cause of pain on the outer side of the knee.
Two sets of muscles in the lower leg are also attached to the knee joint: extensors at the front and flexors at the back. The soleus muscle together with the its superficial muscle gastrocnemius are known as calf of the leg. Calf muscle is at the back of the leg which originates from the distal end of the femur through the calcaneal (Achilles) tendon and ends to the calcaneus of the heel. It flexes the knee.
