The motor innervation of the muscle group of the lower extremities is easily remembered since it progresses in a logical pattern. Individual testing and bilateral comparison of the muscle groups is strongly recommended. L3 is responsible for hip flexion. L4 innervates the quadriceps and a lesion at this level will cause a reduced patellar reflex and difficulty in squatting. L5 lesions cause weakness of foot dorsiflexion and great toe extension (difficulty in walking on the heels). S1 radiculopathy is manifested by the inability to flex the calf muscles (difficulty in walking on the toes) and an asymmetric Achilles tendon reflex. L4 compression causes radicular pain or paresthesias in the knee, anteromedial tibia and foot; L5 compression affects the great toe and midportion of the foot; and S1 compression affects the little toe and posterolateral calf.