The effects of intermittent passive exercise on joint stiffness following periarticular fracture in rabbits

To determine the effects of intermittent passive motion on joint stiffness following periarticular fracture, bilateral distal tibia fractures were produced in 31 rabbits. Following immobilization and fracture union at three weeks, one ankle on each rabbit underwent passive exercise daily until sacrifice at six weeks. The contralateral ankle remained immobile, except for weekly stiffness determinations. Passive exercise produced limb swelling and resulted in temporarily decreased ankle stiffness to, but not significantly below, control values. Between exercise sessions, the exercised ankles became significantly stiffer than the contralateral immobilized ankles. The cause of stiffness was not determined, but extrapolation from other work would suggest that the regimens of intermittent passive exercise tested in this study additionally traumatized the healing tissues surrounding the fracture.