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°) 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°). 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° ± 7.4° preoperatively to 86.5° ± 13.5° postoperatively in SE group and 8.7° ± 6.8° to 92.2° ± 16.8° 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.