The lower extremities consist of the feet, legs, and the pelvic muscles.
The feet have more tendons than muscles. These tendons attach the muscles of the calf to the bones in the feet. Some of these muscles include the flexor digitorum longus, flexor hallucis longus, extensor digitorum longus, extensor hallucis longus, lumbricales, dorsal interossei, and plantar interossei.
Other muscles of the calf include the infamous gastrocnemeus which is found on the posterior of the calf. The gastroc, for short, creates the outline on the back of the calf and is prominent when women wear high heels. Under the gastrocnemeus is the soleus which helps the body stand upright. It can get sore during sports like running. The tibialis anterior and tibialis posterior perform opposite functions. The anterior dorsiflexes the foot or lifts the foot up towards the knee. The posterior plantar flexes the foot or send the foot away from the body.
The knee has ligaments that connect one bone to the other. Some of the main ligaments are the anterior cruciate ligament (ACL) that prevents hyperextension, medial cruciate ligament (MCL) that prevents the knee from moving out to the side, the posterior cruciate ligament (PCL) prevents hyperflexion, the lateral cruciate ligament (LCL) that keeps the knee from going in, and the meniscus that is a buffer between the bones in the knee.
The main muscles on the anterior side of the thigh are the quadriceps. This is a group of four muscles, the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedias. These powerful muscles extend the leg. The opposing muscles on the posterior side of the leg are the hamstrings. There are three hamstrings, the biceps femoris, semimembranous, and semitendionsus. These muscles flex the leg. The adductors, gracilis, and sartorius are found on the inside or medial part of the thigh. The adductors bring the legs together. The gracilis also brings the legs together and it flexes the leg. The sartorius is the longest muscle in the body and it flexes the thigh. The tensor fasciae latae on the lateral part of the thigh, abducts the thigh.
The pelvis has a variety of muscles that assist in rotation and abduction of the thigh. The largest and most superficial in the pelvis is the gluteus maximus. This muscle extends the thigh and rotates the hip. Under that is the gluteus medius that rotates and abducts the thigh. The deeper muscles are the gluteus minimus and piriformis. The gluteus minimus also rotates and abducts the thigh. The piriformis is used to hold the femur in place and it rotates the hip. There are a few deep lateral hip rotators as well, the gemellus superior, gemellus inferior, obturator internus, and quadratus femoris.