Return-to-Sport Decision After ACL Reconstruction With a Stiff Knee
A 19-year-old recreational basketball player is 7 months post primary ACL reconstruction with hamstring autograft. He has completed formal physical therapy and wants to be cleared for full basketball. On exam: knee flexion 125 degrees, extension lag 5 degrees, quadriceps limb symmetry index (LSI) 78%, hamstring LSI 85%, single-leg hop for distance LSI 82%, and a Y-balance anterior reach deficit of 6 cm. He reports no pain, no giving way, and has been doing plyometrics in an unsupervised gym. His surgeon's note says 'cleared for sport at 9 months.'
1. Should he be cleared for full basketball now? Justify your answer with the specific data.
Read the worked answer
No. The data show multiple unmet criteria:
- Extension lag of 5 degrees - a stiff knee alters gait and landing mechanics and increases reinjury risk.
- Quadriceps LSI 78% - below the commonly used ≥90% threshold for return to sport.
- Hamstring LSI 85% - below threshold.
- Single-leg hop LSI 82% - below the ~90% threshold.
- Y-balance anterior asymmetry of 6 cm - indicates residual dynamic control deficit.
These deficits cluster and indicate incomplete neuromuscular recovery despite being 7 months out. The surgeon's '9 months' note is a general timeline, not an individualized clearance; the physical therapist's functional assessment should drive the decision.
Recommendation: do not clear; continue targeted rehabilitation with re-testing in 4-6 weeks. Document the specific deficits and the rationale, and communicate with the surgeon and athlete.
2. What specific interventions would you prioritize, and what would you require before re-testing?
Read the worked answer
Priorities:
- Restore full extension - low-load, long-duration stretching, prone hangs, and quadriceps setting; extension lag is a mechanical and functional priority.
- Quadriceps strength - progressive loading, blood flow restriction if tolerated, and open- and closed-chain work.
- Hamstring strength - given hamstring autograft, address donor-site deficits with eccentric loading.
- Neuromuscular control - supervised plyometrics and landing mechanics rather than unsupervised gym work.
- Address the Y-balance deficit with single-leg balance and reach progressions.
Re-test criteria before clearance:
- Extension lag ≤5 degrees (ideally 0), flexion ≥130 degrees.
- Quadriceps and hamstring LSI ≥90%.
- Hop tests LSI ≥90% with good landing quality.
- Y-balance asymmetry <4 cm.
- Completion of a supervised sport-specific progression including cutting and jumping.
Re-test in 4-6 weeks; if criteria are not met, extend. Emphasize that time since surgery alone is not a clearance criterion.