The gastrocnemius is the superficial, diamond-shaped calf muscle visible on the posterior lower leg, forming the largest and most prominent part of the calf complex. Its two heads originate from the posterior femoral condyles, making it one of the few lower leg muscles to cross the knee, and merge with the soleus to form the Achilles tendon, the strongest tendon in the body. It is the primary power generator for push-off during walking and running, working explosively during jumping and sprinting.
| Origin | Posterior surface of the medial femoral condyle; Posterior surface of the lateral femoral condyle |
|---|---|
| Insertion | Posterior surface of the calcaneus via the Achilles tendon, shared with the soleus |
| Nerve Supply | Tibial nerve (S1, S2) |
| Blood Supply | Sural branches of the popliteal artery |
| Actions | Plantarflexion of the ankle; Flexion of the knee (when the ankle is free); Supination of the foot during plantarflexion |
|---|
Because it crosses both the knee and ankle, the gastrocnemius is most effective as a plantarflexor when the knee is extended, stretching it properly therefore requires the knee to be straight, whereas calf raises with a bent knee preferentially target the soleus.
Gastrocnemius tears, sometimes called 'tennis leg', are a common clinical presentation in middle-aged athletes, most often involving the medial head at its musculotendinous junction, producing sudden sharp calf pain during a push-off or acceleration movement. The gastrocnemius is also a key contributor to Achilles tendinopathy load, making calf strengthening programmes, particularly heavy eccentric heel drops, a mainstay of treatment. Deep vein thrombosis in the posterior compartment can mimic a calf strain closely and must be excluded before aggressive rehabilitation.
The two heads of the gastrocnemius are visible and easily palpable as the bulge of the calf, with the medial head typically larger and lower than the lateral. The medial head musculotendinous junction, the most common tear site, is found just above the midpoint of the posterior calf.
A partial or complete tear of the medial head musculotendinous junction during a push-off or sudden acceleration, producing an immediate sharp calf pain often described as feeling like a kick, followed by bruising that tracks toward the ankle over 24–48 hours.
Degenerative changes in the Achilles tendon shared by the gastrocnemius and soleus, producing mid-portion stiffness and pain that is worst after rest and with initial activity, typically responsive to a heavy slow resistance programme.
Complete failure of the Achilles tendon, most commonly 2–6 cm above its calcaneal insertion, producing a sudden audible pop and immediate inability to push off, with a positive Thompson test confirming the diagnosis.
