Increased symptoms of stiffness 1 year after total knee arthroplasty are associated with a worse functional outcome and lower rate of patient satisfaction.

PURPOSE: Symptoms of stiffness after total knee arthroplasty (TKA) cause significant morbidity, but there is limited data to facilitate identification of those most at risk after surgery. Stratifying risk can aid earlier directed treatment options.

METHODS: A retrospective cohort consisting of 2589 patients undergoing a primary TKA was identified from an established arthroplasty database. Patient demographics, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and short form (SF) 12 scores were collected pre-operatively and 1 year post-operatively. In addition, patient satisfaction was assessed for 1 year. Patients with a worse WOMAC stiffness score in 1 year were defined as the "increased" stiffness group and the other cohort as the non-stiffness group.

RESULTS: At 1 year after surgery 129 (5%) patients had a significant increase in their stiffness symptoms (20%, 95% confidence interval (CI) 17.9-22.0, p < 0.001), and had significantly (all p < 0.001) less of an improvement in their pain, function and total WOMAC scores, and SF-12 scores compared to the non-stiffness group (n = 2460). Patient satisfaction was significantly lower (odds ratio (OR) 0.178, CI 0.121 to 0.262, p < 0.001) for the increased stiffness group. Logistic regression analysis identified male gender (OR 1.66, p = 0.02), lung disease (OR 2.06, p = 0.002), diabetes (OR 1.82, p = 0.02), back pain (OR 1.81, p = 0.005), and a pre-operative stiffness score of 44 or more (OR 5.79, p < 0.001) were significantly predictive of increased stiffness.

CONCLUSION: Patients with increased symptoms of stiffness after TKA have a worse functional outcome and a lower rate of patient satisfaction, and patients at risk of being in this group should be informed pre-operatively.

LEVEL OF EVIDENCE: Retrospective prognostic study, Level III.