Biomechanics and Orthopedics
Core concepts
Understand normal gait: heel strike, midstance, toe-off, and the role of the subtalar joint in shock absorption and propulsion. Know the windlass mechanism, the first ray, and the relationship between pronation/supination and common pathology (plantar fasciitis, tibialis posterior dysfunction, lateral ankle sprain). Familiarize yourself with the physical examination maneuvers for each condition and the orthotic principles-medial posting for excessive pronation, lateral posting for supination, and the role of rocker-bottom soles for rigid deformity. Know common pediatric conditions (intoing, flatfoot, toe walking) and when they are physiologic versus pathologic.
Traps in questions
A frequent trap is confusing pronation with supination and applying the wrong orthotic correction. Another is missing that a rigid flatfoot is pathologic (tarsal coalition, arthritis) while a flexible flatfoot may be physiologic. Questions often test the windlass mechanism and the role of the plantar fascia in arch support.
Rule of thumb
Match the orthotic to the deformity: post medially for excessive pronation, laterally for supination, and use rocker-bottom soles for rigid deformities that cannot adapt.
Worked example
A runner with medial arch pain worse in the morning has plantar fasciitis. The windlass mechanism explains the pain: dorsiflexion of the toes tightens the fascia, so stretching and orthotic support are key.