The physical therapist has recognized the importance of evaluating foot and ankle function in patients who have spinal and lower extremity dysfunction. The ability to properly evaluate a joint requires a thorough understanding of the biomechanics of the involved articulations. This paper presents the clinician with a concise explanation of the biomechanical functions required of the foot during the walking cycle. A detailed description of two of the primary joints responsible for performing these functions are also reviewed. J Orthop Sports Phys Ther 1985;7(2):69-72.