The plantaris has a tiny muscle belly (7-10 cm) producing the longest tendon in the body (30-45 cm). Its vestigial motor function is negligible — its primary clinical significance is as a tendon graft donor. Absent in 7-10% of individuals. The plantaris muscle belly tears in tennis leg — acute tearing of the muscle belly between the gastrocnemius and soleus produces a sharp calf pop with immediate swelling and bruising.
| Origin | Lateral supracondylar ridge of the femur (just above the lateral gastrocnemius head) |
|---|---|
| Insertion | Medial calcaneus — between the gastrocnemius and the Achilles tendon |
| Nerve Supply | Tibial nerve (S1, S2) |
| Blood Supply | Popliteal and sural arteries |
| Actions | Weak plantarflexion of the ankle; Weak knee flexion; Primary function as a tendon graft donor (the longest tendon in the body — 30-45 cm) |
|---|
Tennis leg classically presents as a sudden sharp pain in the medial posterior calf during explosive push-off in tennis or other sports, followed by significant bruising tracking down the medial calf. MRI shows the fluid collection between the medial gastrocnemius and soleus at the musculotendinous junction level. The injury is to the plantaris muscle belly or the medial gastrocnemius medial head — managed conservatively with compression, elevation, and early mobilisation.
The plantaris muscle is not palpable separately from the lateral gastrocnemius. Its tendon is palpable in the posterior calf between the Achilles and soleus after harvest.
Plantaris or medial gastrocnemius tear producing acute calf pop and bruising managed with RICE protocol and progressive rehabilitation.
