The plantaris muscle: too important to be forgotten. A review of evolution, anatomy, clinical implications and biomechanical properties.

Plantaris muscle (lat. musculus plantaris) is a fusiform muscle of the superficial posterior leg compartment, characterized with a small muscle belly and very long and slender tendon. Many anatomical variations of plantaris muscle have been reported previously, including its inconstancy. Evolutional studies strongly suggest that plantaris muscle is a rudimentary muscle that plays minor role in gait biomechanics. However, plantaris muscle seems to have very important proprioceptive role since it has very high density of muscle spindles. Clinically, plantaris muscle is involved in differential diagnosis of posterior leg pain and several pathological entities such as: plantaris muscle rupture, non-insertional Achilles tendinopathy and popliteal artery compression syndrome. Different surgical specialties have recognized plantaris muscle tendon as a valuable graft. However, literature on plantaris muscle tendon biomechanical properties is rather scant and inconsistent with several limitations for proper data comparison and interpretation. Further comparative studies are needed to properly define biomechanical properties of plantaris muscle tendon grafts for various ligament and tendon reconstructive procedures.