Post-operative knee stiffness (flexion < 90 degrees) occurs in 1.3%-12% of patients who undergo TKA. The preoperative risk factors for stiffness include decreased preoperative range of motion, age, diabetes mellitus, and socioeconomic status. Surgical factors can also contribute, including overstuffing the patellofemoral joint, tight flexion/extension gaps, and excessive tightening of the extensor mechanism. If left untreated, loss of flexion negatively impacts functional outcomes, patient satisfaction, and the ability to perform activities of daily living. MUA is considered the initial management for patients with flexion less than 90 degrees.
