There is little knowledge of the functional performance of patients with talocalcaneal coalition because of the marginal quantitative information accessible using current motion-analysis and plantar pressure-measurement techniques. A novel system was developed for comprehensively measuring foot-floor interaction during the stance phase of gait that integrates instrumentation for simultaneously measuring bony segment position, ground reaction force, and plantar pressure with synchronization of spatial and temporal variables. An advanced anatomically based analysis of foot joint rotations was also applied. Tracking of numerous anatomical landmarks allowed accurate selection of three footprint subareas and reliable estimation of relevant local forces and moments. Eight patients (11 feet) with talocalcaneal coalition were analyzed. Major impairment of the rearfoot was found in nonsurgical patients, with an everted attitude, limited plantarflexion, and overloading in all three components of ground reaction force. Surgical patients showed more normal loading patterns in each footprint subarea. This measuring system allowed for accurate inspection of the effects of surgical treatment in the entire foot and at several footprint subareas. Surgical treatment of talocalcaneal coalition seems to be effective in restoring more physiologic subtalar and forefoot motion and loading patterns.