Fixed flexion deformity following total knee arthroplasty. A prospective study of the natural history.
INTRODUCTION: Stiffness following total knee arthroplasty (TKA) is a disabling problem resulting in pain and reduced function. OBJECTIVE: The aim of our study was to evaluate the natural course of fixed flexion deformity (FFD ) following primary total knee arthroplasty. METHODS: Prospective review of 1626 patients undergoing primary TKA from 2001 to 2006 with a minimum of 4 year follow up. Demographic data included post-operative range of motion; type of prosthesis used, treatment modalities for stiffness and the final range of motion were recorded. FFD was defined as class 1(5-15 degrees) and Class 2 (> 15 degrees). Patients with a pre-operative FFD of >15, infection, stiffness treated with manipulation or revision surgery were excluded from the study. RESULTS: Of the 1626 patients evaluated, 170 (10.5%) presented with a FFD. 18 patients were excluded from the study and 16 were lost to follow up. 124 (91.2%) were class 1 and 12 (8.8%) were class 2. FFD improved from a mean of 8.8 degrees to 0.4 degrees (p<0.0001) in 11.4 months. In 94.1% patients the FFD completely resolved (i.e. < 5 degrees) at a mean of 10.8 months (p<0.0001). In the remaining 5.9% of patients, FFD improved from a mean of 16.4 to 6.9 degrees at a mean follow up of 21.5 months (p<0.0001). CONCLUSION: A gradual improvement in the FFD can be expected up to 2 years and a small residual flexion contracture does not cause functional deficit. LEVEL OF EVIDENCE: Prospective cohort study, level 3.