Os Trigonum (OT) and Stieda Process (SP), separate or extensive ossification of the lateral tubercule of poste- rior face of Talus (TA), respectively, are indicative of causal factors of the Posterior Impingement Syndrome of The Ankle (PISA) - disturbance, sharp or chronic pain, with pain in the posterior region of the ankle caused by foot movements. The objective of this study was to analyze the morphological importance of the presence of OT and or SP and the possible relationship with PISA for which we used 80 dry TA. The morphometry of TA and Lateral Tubercule of TA (LT) were calculated and expressed as mean: LTA= total length of TA; WTA= total width of TA; LLT/LPS= total length of LT/SP; TLT= total thickness of LT/SP. The measures were LTA: 55.22 (±4.16) mm; WTA: 39.51 (±2.46) mm; LLT/LPS: 8.06 (±2.14) mm; TLT: 8.46 (±1.01) mm. Our results provide useful information not found in the specialized literature and are of assistance in the diagnosis and treatment of PISA.

KEY WORDS: Os Trigonum; Stieda Process; Talus; Foot Anatomy.