The Anatomy of the Lower Leg Muscles

The lower leg lies between the knee and the ankle. There are many muscles located in the lower leg, but there are three that are particularly well known: the gastrocnemius and the soleus, which are the most powerful muscles in the lower leg, and the anterior tibialis. The Achilles tendon is also located in the lower leg.

The lower leg is made up of two very strong, long bones: the tibia and the fibula. The tibia, also known as the shin bone, is the stronger and larger of the two. It is located toward the middle of the lower leg. The fibula, or calf bone, is smaller and is located on the outside of the lower leg.

The lower leg is also home to nerve fibers, including the superficial fibular nerve, the deep fibular nerve, and the tibial nerve. The primary muscle in this part of the body is the gastrocnemius, which gives the calf its signature bulging, muscular appearance.

The anterior tibial, posterior tibial and fibular arteries are responsible for blood supply to the lower leg. The lower leg makes up a large portion of an individual's overall body weight. It is an essential structure for any weight-bearing activity, such as walking, stand, running or jumping. Common conditions that affect the lower leg include stress fractures, compartment syndrome, shin splints, and muscle tears.

The lower leg is divided into four compartments that contain the various muscles of the lower leg: anterior, lateral, posterior and deep posterior.

• The anterior compartment, in the front of the shin, holds the tibialis anterior, the extensor digitorum longus, the extensor hallucis longus, and the peroneus tertius muscles. These muscles pull the toes and feet upward, a process known as dorsiflexion. The tibialis anterior also assists in turning the foot inward. You can feel these muscles contract by placing your hand just to the outside of the tibia and pulling your foot up.
• The lateral compartment is along the outside of the lower leg. It contains the peroneus longus and peroneus brevis muscles. These muscles pull the toes and feet outward. They also help with pointing the foot, or plantarflexion. To feel these muscles contract, place your hand on the outside of your shin and turn your foot out.
• The posterior compartment holds the large muscles that we know as the calf muscles: the gastrocnemius and soleus. This compartment also contains plantaris muscle. The gastrocnemius is shorter, thicker and has two inner and outer attachments. It is the most visible of the calf muscles. The soleus lies underneath. These three muscles attach to the Achilles tendon, and they all aid with plantarflexion.
• The deep posterior compartment lies deep within the back of the lower leg. It includes the tibialis posterior, the flexor digitorum longus and the flexor hallucus longus. The tibialis posterior pulls the foot inward, the flexor digitorum longus flexes the toes the and flexor hallucus longus flexes the big toe. All three aid in plantarflexion.