A muscle variant in the region of the popliteal fossa associated with the semitendinosus muscle

Posterior thigh pain is frequently caused by straining the posterior thigh muscles. Because of these clinical implications, it is important for surgeons to have a comprehensive knowledge of muscle variations. During a routine dissection class at Ross University School of Medicine, a 57-year-old male cadaver presented with a unilateral muscle variation of the semitendinosus.

In this case, an accessory muscle appears to originate from the belly of the semitendinosus muscle and passes down, through the popliteal fossa, to insert between the medial and lateral heads of the gastrocnemius muscle. The variant muscle may have compressed the popliteal vein and part of the tibial nerve during its pathway with potential implications for muscle function in the leg and foot. To the best of the author’s knowledge, such a rare anatomical variation has not yet been reported in the literature before.