Unicompartmental Knee Arthroplasty Patients Recover More Like Total Hip Patients Than Total Knee Patients: A Prospective Longitudinal Study

The differences in physical activity (PA) recovery between patients who have total hip arthroplasty (THA), unicompartmental (UKA), and total knee arthroplasty (TKA) are lacking. We described the trajectory of recovery based on objective metrics of PA over the first 12 months post-joint arthroplasty (JA). Data from 4,700 patients who underwent a primary unilateral JA surgery between November 2018 and September 2021 from a multi-site prospective study were analyzed. Generalized estimating equations, with an unstructured correlation matrix, were used to evaluate objective PA metrics over time, and the appropriate post-estimation commands were used to compare scores between time intervals. The PA (step count, stair count, gait speed, gait asymmetry) metrics were recorded pre-JA and one, three, six, and 12 months post-JA. Recovery curves were created using longitudinal estimating equations. All groups showed significant improvement in PA metrics over the first 12 months post-JA (all, P < 0.001). The THA and UKA patients were similar at almost all time points in terms of step count, stair count, gait speed, and gait asymmetry, while TKA patients had significantly lower PA scores in nearly all metrics (P < 0.05). The largest margin of meaningful improvement in PA was obtained by three months across all groups, with marginal additional improvement being made up to 12 months post-JA. This study shows early PA improvement post-JA with the greatest recovery being observed in patients post-THA and UKA compared to those post-TKA. Patients can expect the greatest proportion of PA recovery by three months for most PA metrics with less meaningful improvements from six to 12 months post-JA. Clinicians can use this data to educate patients perioperatively, set realistic expectations, and monitor recovery following JA.