"Tennis leg": gastrocnemius injury is a far more common cause than plantaris rupture.

We report a typical case of "tennis leg", in which the main finding was a fluid collection between the medial head of the gastrocnemius and soleus muscles. Since the first clinical description of this entity in 1883, the injury has been attributed to rupture of the plantaris tendon. However, recent studies of this condition with sonography and magnetic resonance imaging have shown that most of these cases are actually due to injury to the gastrocnemius and/or soleus muscles, and up to 10% are due to deep venous thrombosis masquerading as muscle injury. The plantaris muscle and tendon are only rarely involved in this injury.