# Elevated risk of patellofemoral osteoarthritis following ACL reconstruction compared to contralateral knees: A systematic review and meta‐analysis

## TL;DR

This study finds that patients who undergo ACL reconstruction are more likely to develop patellofemoral osteoarthritis in the treated knee compared to the untreated one.

## Contribution

The study is the first to systematically compare the risk of patellofemoral osteoarthritis in ACL-reconstructed knees versus contralateral knees using a meta-analysis.

## Key findings

- ACL-reconstructed knees had a significantly higher likelihood of patellofemoral osteoarthritis compared to contralateral knees.
- No significant difference in PFOA risk was found between patellar tendon and hamstring autografts.
- The pooled analysis included 1206 participants with an average follow-up of 5 years.

## Abstract

To investigate the development of patellofemoral osteoarthritis (PFOA) in the affected knee of anterior cruciate reconstruction (ACL‐R) patients compared to their contralateral knee. The impact of graft choice on PFOA progression was also examined.

A systematic literature search was performed up to 1 June 2025. Studies at level of evidence II and III reporting imaging outcomes of the patellofemoral (PF) joint following ACL‐R and contralateral knees were included. Studies involving isolated primary ACL‐R procedures, regardless of meniscus status, were considered. The meta‐analysis was performed to assess if ACL‐R was associated with a higher likelihood of PFOA compared to contralateral knees. Furthermore, a sub‐analysis was conducted to evaluate whether the patellar tendon autograft was associated with a higher chance of PFOA than hamstring autografts. The random effects model was used to calculate the pooled odds ratio of PFOA in patients following ACL‐R compared to the control group. Meta‐regression analysis was performed to determine whether sample size, follow‐up duration and population age significantly influenced the odds ratio.

Eleven studies met the inclusion criteria and were included in this review. A total of 1206 participants were included, with an average male/female ratio of 57/49 and a pooled weighted mean age of 27 years. The follow‐up duration varied from 1 to 17.8 years, with an average of 5 years. Radiographic definitions of PFOA were determined using the Kellgren–Lawrence and the Osteoarthritis Research Society International (OARSI) classifications, while the magnetic resonance imaging (MRI) PFOA definition was derived from the MRI Osteoarthritis Knee Score (MOAKS) grading. Patients undergoing ACL‐R demonstrated a significantly higher likelihood of PFOA compared to their contralateral knees (p = 0.01). The use of patellar tendon or hamstring autografts did not show significant differences.

Patients undergoing ACL‐R are more likely to develop PFOA than their contralateral knees. No significant difference in risk of PFOA development was found between hamstrings tendon and patellar tendon autografts.

Level II and III, systematic review and meta‐analysis studies.