Muscle Anatomy:  Material to Study

Leg Model

Certain muscles that are located on the thigh cross both the hip joint and the knee joint and so they have different actions at each joint.  For instance, the rectus femoris causes flexion at the hip and extension at the knee.  Rectus femoris is the central superficial muscle in the quadriceps group:  a group of 4 muscles on the anterior thigh that insert via the patellar tendon at the tibial tuberosity.  "Quadriceps" means 4 heads, head being a term for the origin of a muscle.  The muscles in the quadriceps group are:  rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

The sartorius is another muscle with actions at both the hip (flexion and lateral rotation) and knee (weak flexion).  The sartorius is the strap-like muscle crossing the front of the thigh diagonally.  Just medial to sartorius at the top of the thigh is adductor longus.  The muscles in the adductor group are easier to see in the medial view of the leg model.

The only muscle that abducts the thigh and is clearly visible on the model is the tensor fasciae latae. This muscle is so named because it inserts into a wide band of connective tissue called the fascia lata.  The central thickened part of the fascia lata is called the iliotibial tract or iliotibial band.  The IT band helps to stabilize the knee.

On the posterior side of the thigh is the hamstring group, which consists of two medial muscles, semimembranosus and semitendinosus, and one lateral muscle, biceps femoris.  These muscles all have their origin on the ischial tuberosity and their insertions on the bones of the lower leg on either side of the knee.  Thus they have two actions:  extension of the thigh and flexion of the knee.  The hamstring tendons are the cords of tissue that you can feel at the back of your knee.  Powerful extension of the thigh (such as when one is climbing stairs) is performed by the gluteus maximus.

The medial view of the thigh allows you to see the adductors, known colloquially as the groin muscles.  Gracilis is a thin strap-like muscle that runs along the middle of the medial thigh.  Although adductor magnus is visible in this view, it isn't highlighted because it is mostly deep to other muscles and can be confusing to identify on this model.  Similarly, semitendinosus and semimembranosus are visible in this view but difficult to distinguish on the model.

On the anterior part of the lower leg are two muscles that perform dorsiflexion:  tibialis anterior and extensor digitorum longus.  Extensor digitorum longus is the lateral muscle whose tendon runs under the white band and then fans out to attach to bones of the four little toes.

The posterior lower leg has the much stronger muscles that perform plantar flexion:  gastrocnemius and soleus.  (Although soleus is a large muscle, I am not requiring you to identify it because it is deep to gastrocnemius and difficult to see on the model).  If you hold your leg in the air, pointing your toe is plantar flexion.  This action is important for pushing off when walking or jumping or peddling a bicycle.

Also visible in the posterior view is fibularis longus. This muscle causes eversion, which is turning of the sole of the foot outward.