Return to play: the criteria most clinicians underweight.
Time-based return is the lazy default. Criteria-based return — strength symmetry, sport-specific load tolerance, psychological readiness — produces lower re-injury rates across virtually every condition that has been studied.
Time-based return to sport — 'six weeks for a hamstring, nine months for an ACL' — is the lazy default of return-to-play planning. Criteria-based return outperforms it on virtually every metric that has been studied.
Why time-based return persists
Time-based return is administratively convenient. Insurers like it, schedules respect it, and it gives a clean answer to the question every injured athlete asks first. The problem is that healing time and functional readiness are correlated but not identical, and the cost of misjudgement falls almost entirely on the athlete who returns to a sport-specific load test for the first time inside a competitive match.
The literature is consistent across hamstring strains, ACL reconstruction, ankle ligament injury and post-concussion return: athletes returned on criteria-based protocols re-injure at half to a third the rate of those returned on time alone.
What criteria-based return actually measures
A useful return-to-sport battery covers four domains. Each has measurable thresholds and each tells you something different.
- Strength symmetry — typically a Limb Symmetry Index (LSI) >90% on the involved versus uninvolved limb, measured isokinetically or with single-leg performance tests.
- Functional / performance tests — single-leg hop for distance, triple hop, crossover hop; LSI >90% on each.
- Sport-specific load tolerance — a structured progression of cutting, jumping, accelerating that mimics in-competition demands.
- Psychological readiness — instruments like the ACL-RSI or Tampa Scale of Kinesiophobia capture fear of re-injury, which independently predicts re-injury risk.
Why athletes fail the psychological criterion most often
The strength and functional metrics tend to recover before the psychological metric. ACL-RSI scores below 60 at 'physical clearance' have been shown to predict re-injury independently of any biomechanical measure. Pushing an athlete back onto the field while they still 'don't trust the knee' raises injury risk and shortens career length.
Addressing this is not a separate clinical specialty. Graded exposure to sport-specific tasks — the same progression that builds physical tolerance — also rebuilds confidence. Skipping the gradient is what fails.
What this looks like in practice
For a typical recreational athlete with a moderate hamstring strain, a criteria-based return might run two to three weeks longer than a calendar-based one. The trade is a meaningful reduction in re-injury rate over the following season. For elite athletes, the trade is the same; for most amateurs, the calendar pressure is lower and the case for criteria-based return is even stronger.
Frequently asked
How do I find the right person to assess return-to-sport criteria?
A sports physiotherapist or sport-medicine clinician with experience in your sport is the right starting point. Ask explicitly whether they use criteria-based return testing — many clinics still default to time-based discharge.
Can I do return-to-sport testing on myself?
Strength symmetry and hop tests can be self-administered with reasonable accuracy if you film and measure carefully. Sport-specific load progression and psychological assessment benefit from external eyes.
What if I fail one of the criteria?
Failing one criterion is information, not a verdict. The point of the battery is to identify which capacity still needs work, then target it. Returning anyway is the high-risk path.