Gastrocnemius Muscle Anatomy

Location & Overview

The gastrocnemius muscle is a fundamental muscle of the lower leg used for walking and postural purposes. The gastrocnemius has two heads, a medial and a lateral head. The medial head is generally thicker and wider than the lateral head. These two heads connect to the epicondyles of the femur. Combined together with the soleus, the gastrocnemius forms what is commonly referred to at the ‘calf muscle’. The official term for the grouping of these two muscles is the ‘triceps surae’. Along with the plantaris muscle, these three muscles make up the superficial flexor group of the lower leg. The gastrocnemius is the most superficial of these three muscles, meaning it is closest to the skin’s surface ^{[1] [2] [3]}.

The aponeurosis of the gastrocnemius muscle connects to the calcaneal tendon. The calcaneal tendon is also more commonly known as the ‘Achilles tendon’ and is the longest and widest tendon of the human body. Achilles was a character of Greek mythology who’s entire body was made invulnerable except for the calcaneal tendon, which is where the reference ‘Achilles heal’ comes from in relation to a weakness in spite of overall strength ^{[4] [5] [6]}.

Origin & Insertion

The gastrocnemius has two heads which originate from the lateral and medial condyles of the femur. Its origin also crosses onto the popliteal surface of the femur. As the muscle works its way down the leg, the two heads join together. They then form a large aponeurosis which inserts into the calcaneal tendon. This calcaneal tendon then inserts onto the posterior surface of calcaneus ^{[7] [8]}.

Actions

The first action of the gastrocnemius muscle is to cause plantarflexion of the foot at ankle joint. This action is commonly performed when walking/running/jumping for example during the ‘pushing away’ part of the movement. It also works alongside its neighbour the soleus as part of the triceps surae group to accomplish this. Another action of the gastrocnemius muscle is to cause flexion of the leg at knee joint. However, the gastrocnemius is not able to exert its full power when flexing the knee and plantarflexing the ankle at the same time. Rather, it is most powerful when performing its actions separately ^{[9] [10] [11]}.

Innervation

The gastrocnemius is innervated by the tibial nerve (S1-S2). This nerve innervates the majority of the calf muscle ^{[12] [13]}.

Blood Supply

Blood is supplied to the gastrocnemius via the sural arteries. The sural arteries are collateral arteries of the popliteal artery, which is derived from the femoral artery ^{[14] [15]}.