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The main goals of total knee arthroplasty (TKA) are to provide pain relief, joint stability, and satisfactory range of motion. Generally, a minimum of 90° range of motion in the knee is required in daily activities.1,2 Knee flexion of at least 65° is required in the swing phase of normal gait, and 106° of flexion is necessary to rise easily from a chair or to tie shoelaces.3,4 A range of motion of 0° to 105° is desirable, particularly in patients with involvement of multiple joints.5 In some cases of bilateral hip and knee replacement, combined hip and knee flexion > 190° is necessary.6
Limited range of motion in the knee that presents as stiffness, flexion contracture, or ankylosis may be a severe complication after TKA. This article focuses on the etiology, prevention, treatment options, and prognosis of this severe complication.
THE PROBLEM
An ankylosed knee is defined as one with 0° of motion and a stiff knee, a total range of motion <50°, or a flexion contracture of >20°, or both.7
Permanent flexion or extension contracture after TKA not only produces problems with motion but also usually causes pain.8·9 In a stiff knee with severe flexion contracture after TKA, weight bearing may put an excessive load on the back of the posterior condyles of me femoral component and on the posterior one half of the tibial plateau of the polyethylene linear insert.10 The quadriceps force required to stabilize the flexed knee during weight bearing increases with increasing flexion of me knee and may lead to impaired endurance and function clinically."
INCIDENCE
The frequency of limited knee flexion after TKA is difficult to assess from the reports in the literature and depends on the criteria used to determine "acceptable" range of motion versus "stiffness" or unacceptable motion. The rate of fibrous ankylosis as a complication of TKA has been reported to be 0.1%.12 In anotJier series, which spanned a 21 -year period and involved multiple designs, postoperative knee stiffness (defined as range of motion <50°) was present in 0.3% of patients.13
ETIOLOGY
The cause of stiffness after TKA may not be clear for every patient and may be multifactorial. Factors that do not affect knee flexion after TKA are patient gender and age,9 extent of...