Step count recovery patterns in the first six weeks after knee replacement in individuals with knee osteoarthritis: a secondary analysis of a prospective observational cohort study using wrist-worn accelerometry.

Effective patient education and activity expectation-setting following knee replacement requires understanding postoperative recovery patterns. We investigated step-count recovery patterns, identified recovery trajectory clusters, and examined differences in postoperative outcomes and preoperative factors associated with those clusters. Using wrist-worn accelerometer, step-counts were measured for one week preoperatively and six weeks postoperatively in patients with knee osteoarthritis undergoing total or unicompartmental knee replacement (UKR). Patient-reported outcomes (OKS, EQ-5D-3L, EQ-VAS) were collected preoperatively and at six postoperative weeks. The proportion of participants exceeding their preoperative step-count was calculated. Latent class growth analysis identified trajectories of absolute (postoperative) and relative (postoperative-to-preoperative ratio) step-counts. Kruskal-Wallis with Dunn's test assessed differences in postoperative outcomes across trajectories, and multinomial logistic regression assessed associations between trajectories and preoperative factors. Eighty-two participants (aged 42-89 years; 52% women) were included. Within six weeks, 32% exceeded preoperative step-counts. Three trajectories (high, moderate and low recovery) were identified for both absolute and relative step-counts. For absolute steps, the "high recovery" group (n = 30, 37%) began with a median of 991 steps [IQR 1,335] at Week1 and achieved a median of 6,606 steps [IQR 2,940] by Week6. This compares to the "moderate" group (n = 24, 29%) who improved from 360 steps [IQR 481] at Week1 to 3,739 steps [IQR 1,918] at Week6, and the "low" group (n = 28, 34%) who increased from 29 steps [IQR 176] at Week1 to 1,452 steps [IQR 1,504] by Week6. For relative steps, the "high recovery" group (n = 39, 47%) reached 92% [IQR 29%] of their preoperative step-count at Week6, compared with 64% [IQR 25%] in the "moderate" group (n = 26, 32%) and 31% [IQR 7%] in the "low" group (n = 17, 21%). Patients in the high recovery trajectories reported less pain, better knee function (OKS) and better health status at six weeks versus low recovery trajectories. Membership of the high trajectories was more likely in those with higher preoperative step-count and for those managed with UKR. Patients with lower preoperative step-count were unlikely to achieve high absolute step-count and less likely to achieve high- or moderate-relative recovery trajectories versus those with a higher preoperative step-count. One in three individuals regained preoperative step-count by six weeks, with heterogeneity in recovery patterns. Greater recovery was associated with higher preoperative step-count and UKR procedures.