Equivocal Physical Activity Outcomes 10 Years After Patellofemoral vs Total Knee Replacement: Follow-Up of a Previously Reported Randomised Controlled Trial in Isolated Patellofemoral Joint Osteoarthritis

INTRODUCTION: The purpose of this study was to determine differences in physical activity amongst patients who had had a total knee replacement (TKR) or patellofemoral joint replacement (PFR), in a randomised controlled trial, 10 years after surgery.

METHODS: Patients with isolated patellofemoral joint osteoarthritis (PFJ OA) were recruited to a randomised controlled trial. Patients were randomised 1:1 to PFR or TKR between 2007 and 2014. Patients were invited back to participate 10 years later. Those who accepted wore a GENEActiv wrist-worn accelerometer for 7 days. The duration of inactivity, light, moderate, and vigorous activity was compared between groups. Total physical activity, total step count, and 24-hour (Euclidean norm minus 1g- ENMO) acceleration were measured and compared using T-tests or Wilcoxon tests.

RESULTS: There were a total of 30 patients recruited as part of the study; 17 patients had a PFR, and 13 patients had a TKR. PFR patients did an average of 2% more minutes of total physical activity, 1154.2 minutes per week, compared to TKR patients, 1132.1 minutes per week; no significant difference was found (p=0.89). PFR patients had a 8.6% higher step count compared to TKR patients per week, but did not show a statistically significant difference p > 0.05. There was no statistically significant difference between the duration of light, moderate and vigorous activity performed.

CONCLUSION: Although PFR had a higher step count and total physical activity per week, this was there was no statistically significant difference in physical activity levels between PFR and TKR participants at the 10-year follow-up.

LEVEL OF EVIDENCE: Level 2.