Gastrocnemius, soleus and plantaris, the triceps surae, supplied by the tibial nerve
Mnemonic
“Gastrocnemius, Soleus, Plantaris”, the superficial compartment, all inserting via the Achilles (calcaneal) tendon and supplied by the tibial nerve:
- Gastrocnemius - two heads from the femoral condyles, so it crosses the knee as well as the ankle
- Soleus - from the tibia and fibula, crossing the ankle only
- Plantaris - small, absent in about 10 per cent, with a long thin tendon
“Gastrocnemius crosses two joints, soleus only one”, which is the basis of the Silfverskiold test: if ankle dorsiflexion improves with the knee flexed, the tightness is in gastrocnemius; if not, it is in soleus.
Soleus is the calf muscle pump, its venous sinuses emptying with each contraction, which is why immobility causes deep vein thrombosis and why calf exercises are prescribed.
Simmonds’ (Thompson’s) test for Achilles rupture: squeezing the calf with the patient prone produces no plantarflexion if the tendon is ruptured.
Expansion
- Gastrocnemius
- Soleus
- Plantaris
Together the gastrocnemius and soleus form the triceps surae, insert via the Achilles (calcaneal) tendon, and powerfully plantarflex the ankle. All are supplied by the tibial nerve.