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.
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.
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.
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.