Early ACL Reconstruction or Rehab First
An ACL tear can end a young athlete's season, and choosing early surgery or rehab first shapes the knee's stability, meniscal health and function for decades.
Key terminology
- Anterior cruciate ligament (ACL)
- This ligament runs from the lateral femoral condyle to the front of the tibia inside the knee. It stops the tibia sliding forward on the femur and controls pivoting.
- ACL reconstruction
- A tendon graft replaces the torn ligament through tunnels drilled in the femur and tibia. The torn ACL itself is not sewn back together.
- Knee Injury and Osteoarthritis Outcome Score (KOOS)
- This questionnaire scores pain, symptoms, sport function and knee-related quality of life from 0 (worst) to 100 (best). It was the main outcome in the ACL trials.
- Giving way
- The knee suddenly buckles or shifts, usually when the patient cuts, pivots or lands. In an ACL-deficient knee it is the main sign of instability.
- Medial meniscus
- This C-shaped cartilage pad sits between the medial femoral condyle and the tibia. It is firmly attached and backs up the ACL against forward tibial glide.
- Coper
- This patient returns to pivoting activity without an ACL and without episodes of giving way. A noncoper has recurrent instability after the tear.
- Clinically relevant difference
- This threshold is the smallest change in a score that patients would notice. A result can be statistically significant and still fall below it.
Takeaways
- An acute ACL tear can be treated with structured rehab first, saving reconstruction for knees that stay unstable. The KANON trial randomized 121 young active adults (mean age 26) to early ACL reconstruction or rehab with optional delayed reconstruction. Gain in the Knee Injury and Osteoarthritis Outcome Score at 2 years was 39.2 vs 39.4 points (P=0.96), and only 23 of 59 (39%) in the rehab arm had chosen surgery (Frobell et al, N Engl J Med 2010;363:331-342, PMID 20660401).
- The rehab-first result held up long term, and about half of rehab patients never had surgery. At 5 years 51% of the rehab arm had been reconstructed, with no difference in KOOS, meniscal surgery or radiographic arthritis. At 11 years 52% had been reconstructed and KOOS gain was 46 vs 45 points (P=0.67) (Frobell et al, BMJ 2013;346:f232, PMID 23349407; Lohmander et al, NEJM Evid 2023;2:EVIDoa2200287, PMID 38320141).
- Recurrent giving way is the reason a rehab-first patient goes on to reconstruction. Delayed surgery in KANON was offered for symptomatic instability despite rehab. A Cochrane review found no difference in patient-reported function and noted that many patients stayed symptomatic after rehab and later chose reconstruction (Monk et al, Cochrane Database Syst Rev 2016;4:CD011166, PMID 27039329).
- An unstable ACL-deficient knee puts the medial meniscus at risk, so surgery should not drift once it is chosen. Reconstruction >3 months after injury was associated with more medial meniscal tears (OR 2.24) and no more lateral tears. On KANON MRIs the rehab-first arm had more new medial meniscal damage (RR 2.1) and no more lateral damage. Most pooled studies were retrospective, so cause is unproven (Prodromidis et al, Am J Sports Med 2021;49:2551-2562, PMID 33166481; Snoeker et al, Br J Sports Med 2020;54:612-617, PMID 31653779).
- ACL reconstruction restores stability and does not prevent knee arthritis. At 11 years 44% of KANON knees had radiographic arthritis, and new arthritis features scored higher after early reconstruction (2.4 vs 1.0). The Cochrane review found very low-quality evidence of more arthritis in the surgery arm (35% vs 18%) (Lohmander et al, NEJM Evid 2023;2:EVIDoa2200287, PMID 38320141; Monk et al, Cochrane Database Syst Rev 2016;4:CD011166, PMID 27039329).
- A second trial found a small edge for early reconstruction that fell below a clinically relevant difference. COMPARE randomized 167 patients aged 18-65. Early surgery scored 5.3 points better on the IKDC knee score at 2 years (95% CI 0.6-9.9, P=0.026), and the rehab arm scored better at 3 months. Half of the rehab arm (50%) was reconstructed (Reijman et al, BMJ 2021;372:n375, PMID 33687926).
- No early screening test reliably predicts who will cope without an ACL. In 125 ACL-injured patients, 37% screened as potential copers. At 1 year 70% of those screened as noncopers who skipped surgery had become true copers, so the screen had poor prognostic accuracy. A trial of rehab is the better test (Moksnes et al, J Orthop Sports Phys Ther 2008;38:586-595, PMID 18979658).
- Reconstruction does not guarantee a return to competitive sport. Across 69 studies and 7556 patients, 81% returned to any sport, 65% to their preinjury level and 55% to competitive sport. Younger age, male sex, elite level and a positive psychological response favored a return (Ardern et al, Br J Sports Med 2014;48:1543-1552, PMID 25157180).