Third Gastrocnemius Muscle Head: A Case Report

Abstract

Introduction: The gastrocnemius is one of the muscles of the posterior leg. It usually has two heads, which originate from the medial and lateral condyles of the femur respectively. The two heads come together to form the bulk of the muscle and then fuse with the tendon of the soleus muscle to form the calcaneal tendon. This case report documents a unilateral third head of the gastrocnemius muscle. Background: The presence of a third head has recently gained attention for its possible involvement in popliteal vessel entrapment syndrome. The muscle's close proximity to the popliteal artery and vein can potentially cause pain and claudication. Surgical resection of the muscle has been found to provide symptomatic relief, however in one study, 20 out of 1,039 cases found a third head of the gastrocnemius in patients with pain, but without symptoms of claudication. Case Findings: During a detailed dissection of a 74 year-old male cadaver, a third head of the gastrocnemius muscle was found in the right leg. This atypical muscle head originated from the medial third of the lateral femoral condyle, ran inferolaterally across the joint space, merged with the medial aspect of the lateral muscle head. Conclusion: This case report documents a third head of the gastrocnemius. This variant could have possible clinical implications, such as popliteal vessel entrapment. Due to the incidence of a third muscle head in literature, in patients presenting with popliteal claudication symptoms, an atypical anatomical variant etiology should at least be considered by clinicians.