Unterschenkel

Unterschenkel, or lower leg, is the region of the leg between the knee and the ankle. It contains two long bones, the tibia and fibula, bound by the interosseous membrane. The tibia bears most of the body's weight, while the fibula mainly provides stabilization and serves as an attachment site for muscles. Together with surrounding muscles and vessels, these bones form four compartments: anterior, lateral, superficial posterior, and deep posterior.

The anterior compartment houses the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and sometimes fibularis tertius; it dorsiflexes the ankle and extends the toes. The lateral compartment contains the fibularis longus and fibularis brevis, which evert and assist in plantarflexion. The superficial posterior compartment includes the gastrocnemius, soleus, and plantaris, all contributing to plantarflexion of the foot and, for gastrocnemius, knee flexion. The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which plantarflex and invert the foot, and flex the toes.

Nerve supply comes from the sciatic nerve in the popliteal fossa, which divides into the tibial nerve and the common peroneal nerve. The common peroneal nerve further divides into superficial and deep peroneal nerves; the tibial nerve supplies the posterior compartments. Sensory innervation includes branches such as the saphenous and sural nerves.

The arterial supply derives from the anterior tibial, posterior tibial, and fibular (peroneal) arteries. Clinically, the region is associated with shin splints, tibial and fibular fractures, compartment syndrome, and calf strains.