part of part of Homo sapiens calcaneus surface groove groove for tendon of flexor hallucis longus muscle of calcaneus 2026-03-19T00:00:00Z A surface groove running longitudinally along the inferior aspect of the sustentaculum tali of the calcaneus, through which the tendon of the flexor hallucis longus muscle passes distally toward the hallux. The tendon is held within the groove by a fibrous retinaculum. David Osumi-Sutherland