The leg consists of the tibia and fibula. Proximally, the tibia of the leg articulates with the femur of the thigh through the knee joint. Distally, the tibia and fibula of the leg articulate with the talus bone of the foot through the ankle joint. The muscles of the leg that act on the knee and ankle as well as on the joints of the foot are organized into three fascial compartments, similar to those of the thigh muscles (Figure 37-1A). The anterior compartment primarily contains muscles that produce extension (dorsiflexion) and inversion; the posterior compartment primarily contains muscles that produce flexion (plantarflexion) and inversion; and the lateral compartment primarily contains muscles that produce flexion (plantarflexion) and eversion.
A. Cross-section of the right leg. B. Movements of the ankle. C. Muscles of the anterior compartment of the leg.
The ankle (talocrural) joint consists of articulations between the tibia and talus (tibiotalar joint) and the fibula and talus (talofibular joint) and allows for motion primarily in the saittal plane, as (Figure 37-1B) follows:
- Plantar flexion (flexion). Movement in which the angle between the leg and foot increases.
- Dorsiflexion (extension). Movement in which the angle between the leg and foot decreases.
The subtalar joint is formed by articulations between the talus and the calcaneus and allows for motion primarily in the coronal plane, as follows:
- Inversion (prontation). Movement in which the plantar surface of the foot faces medially.
- Eversion (supination). Movement in which the plantar surface of the foot faces laterally.
Muscles of the Anterior Compartment of the Leg
The muscles of the anterior compartment of the leg produce numerous actions because some muscles cross the ankle, foot, and digits, and perhaps a combination of each of these joints (Table 37-1). The muscles in the anterior compartment of the leg have the following similar features:
- Common innervation. Deep fibular nerve.
- Common action. Dorsiflexion.
- Common vascular supply. Anterior tibial artery.
Table 37-1. Muscles of the Leg |Favorite Table|Download (.pdf)
Table 37-1. Muscles of the Leg
Anterior compartment of the leg
Tibia and interosseous membrane
Medial cuneiform and base of metatarsal 1
Dorsiflexion of foot at ankle joint; inversion of foot
Deep fibular n. (L4, L5)
Extensor digitorum longus
Fibula and lateral tibial condyle
Via dorsal digital expansions into digits 2–5
Extension of lateral digits 2–5 and dorsiflexion of foot
Deep fibular n. (L5, S1)
Extensor hallucis longus
Fibula and interosseous membrane
Distal phalanx of great toe
Extension of great tow and dorsiflexion of foot