Calf Strain – Medial Head of the Gastrocnemius Partial Tear! Calf strains are usually due to tears of the medial head of the Gastrocnemius, which usually happens with forceful foot dorsiflexion while the knee is on extension. For many years, the term “tennis leg” has been used to describe rupture of the plantaris muscle or tendon, which courses between the gastrocnemius and soleus muscles. In imaging, any blood seen at the inter muscular space between the gastrocnemius and the soleus was thought to be related to tear of the plantaris. Today, it is known that this finding is overwhelmingly due to partial tears of the medial head of the gastrocnemius with extension of hemorrhage into the inter muscular space through an associated defect/tear of the deep muscle aponeurosis. Better MRI machines, coils and sequences help in the recognition of even small tears of the gastrocnemius muscle fibers associated to calf strains. In this particular case, the US showed an anechoic collection (hematoma) between the gastrocnemius and soleus muscle bellies. Further evaluation with MRI confirmed a posteromedial hematoma (which shows increased T1 signal intensity due to methemoglobin) at the inter muscular space between the gastrocnemius and soleus. Furthermore, the MRI shows discontinuity/tear of the deep aponeurosis with extension of hemorrhage into the inter muscular, inter fascial space. Of interest, posteromedial leg hematomas are commonly misdiagnosed as intra muscular hematomas. Gastrocnemius tears are classified by the pattern of injury; L-, U- or stair step pattern, which is usually better identified on coronal images. Next time you think there is a plantaris tear, make sure to follow the muscle and tendon from origin to insertion – statistically, you’ll find it to be intact!
