Evaluation of Joint Function and Hand Mobility in the Rehabilitation Process Using Kinematic Modeling and Statistical Analysis

Rheumatoid arthritis (RA) progressively alters hand biomechanics, disrupting interjoint coordination and promoting compensatory movement patterns that are insufficiently captured by conventional range-of-motion assessment. This longitudinal case report (n = 1) investigated the functional reorganization of the digital joint chain during rehabilitation using an integrated framework combining kinematic modeling and descriptive statistical analysis. A patient with RA was evaluated at three time points (Day 1, Day 10, Day 20) during a structured physiotherapeutic program. Flexion–extension movements of the dominant index finger were recorded using an inertial measurement unit (IMU)-based system, and kinematic parameters were processed through a MATLAB-based graphical interface to quantify joint behavior. Results demonstrated a progressive redistribution of motion within the digital chain. Distal compensatory flexion decreased, the proximal interphalangeal joint shifted from hyperextension toward functional flexion, and the metacarpophalangeal joint showed increased participation in movement generation. These changes reflect improved interjoint coordination and a more balanced functional organization of the finger. Technology-assisted kinematic assessment provides an objective approach for monitoring rehabilitation-induced adaptations and supports quantitative evaluation of functional recovery in rheumatoid arthritis.