Arthroscopic partial meniscectomy for a degenerative meniscus tear: a 5 year follow-up of the placebo-surgery controlled FIDELITY (Finnish Degenerative Meniscus Lesion Study) trial

Key points

1. 01No clinically relevant difference in knee symptoms or function between APM and placebo surgery at 5 years
2. 02APM group had a 13% higher absolute risk of radiographic osteoarthritis progression (Kellgren-Lawrence grade increase) compared with placebo
3. 03APM group showed greater OARSI sum score progression (adjusted mean difference 0.7, 95% CI 0.1 to 1.3)
4. 04More participants in the APM group reported mechanical symptoms at 5 years (adjusted risk difference 18%, 95% CI 5% to 31%)
5. 05Satisfaction and self-reported improvement rates were similar in both groups (78% vs 84% satisfied; 81% vs 88% improved)

How it was conducted

Design

Multicentre, randomised, participant- and outcome assessor-blinded, placebo-surgery controlled efficacy trial (FIDELITY trial), 5-year follow-up

Participants

146 adults aged 35-65 years (mean 52 years) with MRI- and arthroscopically-verified degenerative medial meniscus tear and no advanced knee osteoarthritis, recruited from 5 Finnish orthopaedic centres

Groups

APM (n=70): removal of damaged meniscus tissue; Placebo surgery (n=76): diagnostic arthroscopy only, simulating APM sounds and sensations

Primary outcomes

Radiographic OA progression (Kellgren-Lawrence grade increase >=1 and OARSI sum score); patient-reported knee symptoms and function (WOMET, Lysholm, knee pain after exercise NRS) at 60 months

Follow-up

60 months (5 years); questionnaires at 2, 6, 12, 24, 36, 48, and 60 months; clinical examination at 24 and 60 months

What they found

• At 5 years, 72% (48/67) in the APM group vs 60% (44/74) in the placebo group had at least one grade progression in radiographic knee OA; adjusted absolute risk difference 13% (95% CI -2% to 28%)
• Adjusted absolute mean difference in OARSI sum score: 0.7 (95% CI 0.1 to 1.3), with more progression in the APM group
• WOMET score at 60 months: APM 84.3 (95% CI 80.1 to 88.6) vs placebo 84.6 (95% CI 80.5 to 88.7); between-group difference -1.7 (95% CI -7.7 to 4.3)
• Lysholm knee score at 60 months: APM 83.7 (95% CI 80.3 to 87.1) vs placebo 85.8 (95% CI 82.6 to 89.0); between-group difference -2.1 (95% CI -6.8 to 2.6)
• Knee pain after exercise at 60 months: APM 2.0 (95% CI 1.5 to 2.6) vs placebo 2.2 (95% CI 1.6 to 2.7); between-group difference -0.04 (95% CI -0.81 to 0.72)
• Mechanical symptoms at 5 years: 29% in APM group vs 12% in placebo group; adjusted absolute risk difference 18% (95% CI 5% to 31%)
• Satisfaction: 78% (APM) vs 84% (placebo); risk difference -0.06 (95% CI -0.19 to 0.08)
• Reoperations: 10% (APM) vs 11% (placebo); risk difference 0.00 (95% CI -0.11 to 0.10)

Limitations

• Crossovers from placebo to APM (intention-to-treat analysis used) may have biased the OA risk estimate towards the null, meaning true APM harm may be underestimated
• Radiographic assessment is inherently subjective and flexion angle was not uniform across all centres, requiring cautious interpretation of joint space width changes
• Only patients with degenerative medial meniscus tears without advanced OA were included, limiting generalisability to traumatic tears or those with more severe OA
• Relatively small sample size (146 participants) means some between-group differences in OA progression did not reach statistical significance

Why it matters

For patients

Middle-aged patients with knee pain from a degenerative meniscus tear should know that meniscus surgery is unlikely to relieve symptoms better than a placebo procedure and may slightly increase the risk of developing arthritis.

For clinicians

These 5-year data reinforce existing guideline recommendations against routine APM for degenerative meniscus tears, and highlight a potential long-term harm of increased radiographic OA progression and mechanical symptoms.

For readers

The FIDELITY trial is one of very few placebo-controlled surgical trials, making its findings particularly reliable; both the lack of benefit and the signal of harm from APM are now supported at the 5-year mark.