Kinematic changes in the rheumatoid arthritic foot are related to pathologies of foot joints and tendons

In rheumatoid arthritis, pathologic changes in structures and in gait kinematics of the foot and ankle occur from onset of the disease. The aim of this study was to explore the relationship between these clinical and kinematic factors at various phases of stance. Foot and ankle kinematics of 25 subjects with RA was assessed and related to the following clinical factors: Magnetic Resonance Imaging scores of joint swelling and erosions and leg tendon involvement, as well as Joint Alignment and Motion scores. The upper and lower confidence intervals of Spearmans correlation coefficient were used to explore the relationships between clinical and kinematic parameters. Maximum first metatarsal-phalange (MTP I) dorsiflexion at pre-swing was related to reduced MTP I passive motion, MTP I synovitis and erosion, midfoot synovitis and erosion as well as hindfoot erosion. Midfoot pronation rang of motion during single-stance was related to subtalar alignment and Achilles tendon involvement. Hindfoot eversion range of motion during single-stance was related to subtalar alignment and peroneus longus tendon involvement. Involvement of the tibialis posterior tendon could not be identified as an independent factor influencing foot or ankle kinematics. In conclusion, changes in gait kinematics could be related to structural pathologies. Such findings may provide guidelines for foot and ankle therapies.