A Comparative Study on the Long-Term Outcome of Total Knee Arthroplasty Performed for Knees Stiff in Extension and Those Stiff in Flexion

Background: Patients with chronic stiff knee with extremely restricted arc of motion (AOM < 20 degrees) may present with stiffness either in extension (stiff in extension [SE]) or in flexion (stiff in flexion [SF]). The difference in the functional outcome after total knee arthroplasty between these 2 groups has not been elaborated in literature. Methods: We retrospectively analyzed 96 patients (115 knees), who had undergone total knee arthroplasty between January 1990 and December 2010 for stiff or spontaneously ankylosed knees (AOM <= 20 degrees). This included 51 knees in SE group and 64 knees in SF group. Results: The average duration of follow-up was 9.7 years (2-17.5 years). The total AOM improved from an average of 10.9 degrees +/- 7.4 degrees preoperatively to 86.5 degrees +/- 13.5 degrees postoperatively in SE group and 8.7 degrees +/- 6.8 degrees to 92.2 degrees +/- 16.8 degrees in the SF group. The mean Knee Society Score in the SE group improved from 23.2 +/- 5.7 preoperatively to 74.1 +/- 8.9 postoperatively and that of SF group from 14 +/- 5.2 to 71.2 +/- 12.5. At 3 months follow-up, Knee Society Score for SE group were higher than that for SF group (P=.03). This difference was not noted beyond 1 year. Complications were noted in 24 (20.9%) knees-10 (23.5%) in SE group and 14 (21.9%) in SF group. Conclusion: The maximum mean AOM achieved was higher in SF group but the incidence of residual flexion contracture was also higher as compared to SE group. The long-term functional outcome scores in SE and SF groups are similar. (C) 2017 Elsevier Inc. All rights reserved.