DO NOT Return to Sport After ACL Surgery... Until You Pass These 5 Tests

By: Tanner Bishop — Physiotherapist, CSCS, MSc PT, BSc Kine, NCCP Coach

Tearing your ACL is one of the most significant injuries an athlete can face. Surgery is only the beginning. What happens during rehab determines whether you get back to sport safely and return to your best.

I don't guess when you're ready. We test, we measure, and we make sure. Here are the five criteria I assess before clearing an athlete for return to sport.

No. 1: Timeline — A Minimum of 9 Months Post-Surgery

Your new ACL graft needs time to heal, mature, and integrate with your body. I respect that biology.

Athletes who return before 9 months have a re-injury rate 7 times higher than those who wait. For every month return is delayed, up to 9 months, re-injury risk drops by roughly 51%.

That doesn't mean you sit around waiting. From 6 to 9 months, we progressively introduce sport-specific work: running, cutting, jumping, and drills that simulate your sport. My goal is that you arrive at 9 months fully prepared, not just having "waited long enough."

No. 2: Quadriceps & Hamstring Strength Testing

Your quads are the most commonly weakened muscle after ACL surgery. Roughly one in three patients achieves adequate quad strength symmetry by 6 months. That's why I test rather than assume.

I require at least 90% Limb Symmetry Index (LSI), meaning your surgical leg produces at least 90% of the force your healthy leg does. Both quadriceps and hamstrings must meet this threshold. Patients at or above 90% quad LSI perform similarly to uninjured individuals, while those below 85% show measurable functional deficits.

I also assess absolute strength relative to your bodyweight, not just symmetry. Your "healthy" leg can lose strength during recovery too, which makes the LSI look artificially good. A percentage of a weakened leg is a low bar.

Why I test this: Weak quads change the way you run, jump, and land, putting your knee in vulnerable positions. Strength symmetry is one of the strongest protective factors against re-injury.

No. 3: Drop Jump Testing (Reactive Strength Index)

Sport demands that your knee absorb force and redirect it instantly. I measure that ability using VALD force deck technology.

The key metric is your Reactive Strength Index (RSI): jump height divided by ground contact time. The minimum thresholds I follow for field sport athletes:

• Bilateral (double leg): RSI > 1.3

• Single leg: RSI > 0.5

I also look for greater than 90% symmetry in jump height and in both concentric and eccentric impulse.

Why I test this: Sport rarely gives you time to think. This test captures your knee's ability to react under rapid, high-force conditions. It closely mimics the exact demands that caused the original injury.

No. 4: ACL-RSI (Psychological Readiness Questionnaire)

Physical readiness is only half the equation.

The ACL-RSI is a validated 12-item questionnaire measuring your emotional readiness, confidence in your knee, and perceived risk of re-injury, scored 0 to 100.

Your mindset directly affects how you move, and the research suggests risk lives at both ends of the scale. Scores that are too low reflect high fear, movement avoidance, and lack of confidence. That shows up as altered landing mechanics, reduced muscle activation, and hesitation during play. Scores at the very top can reflect overconfidence and underestimation of risk, leading to a reckless return before the body is truly ready.

I monitor this throughout your rehab so we can address psychological barriers early, not just at the finish line.

Why I test this: Fear makes you move differently. Overconfidence makes you move carelessly. Both put your knee at risk. I want you confident AND realistic.

No. 5: Triple Hop Test

You hop forward three consecutive times on one leg. I measure total distance on each side and require a minimum 90% LSI compared to the uninjured side.

I'm transparent about this test's limitations. Athletes can achieve symmetrical hop distances while still carrying significant deficits in the surgical knee. Compensating through the hip, or hopping shorter on the healthy side, can mask true weakness. This is why I never use the triple hop in isolation. It is one piece of a larger picture.

Within the broader battery, it tells me about your horizontal power, acceleration, and multi-joint coordination.

Why I Hold These Standards

The landmark Delaware-Oslo ACL Cohort Study found that passing criteria combining time, strength, and function reduced re-injury risk by 84%. Kyritsis and colleagues found athletes who did not meet clinical discharge criteria had a 4 times greater risk of graft rupture.

Each test addresses a different piece of the puzzle: biological healing, strength, reactive ability, psychological readiness, and functional power. I test all five because no single measure tells the whole story.

My commitment is simple: when I clear you, you are fully prepared for your return to sport. That is how I keep my athletes safe and performing at their best.

Book an assesment

References

1. Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. "Simple Decision Rules Can Reduce Reinjury Risk by 84% After ACL Reconstruction: The Delaware-Oslo ACL Cohort Study." British Journal of Sports Medicine 50, no. 13 (2016): 804–808.

2. Beischer S, Gustavsson L, Senorski EH, et al. "Young Athletes Who Return to Sport Before 9 Months After ACL Reconstruction Have a Rate of New Injury 7 Times That of Those Who Return Later." British Journal of Sports Medicine 54, no. 18 (2020): 1117–1123.

3. Cristiani R, Mikkelsen C, Edman G, Forssblad M, Engström B, Stålman A. "Only One Patient Out of Five Achieves Symmetrical Knee Function 6 Months After Primary Anterior Cruciate Ligament Reconstruction." Knee Surgery, Sports Traumatology, Arthroscopy 28 (2020): 3461–3470.

4. Schmitt LC, Paterno MV, Hewett TE. "The Impact of Quadriceps Femoris Strength Asymmetry on Functional Performance at Return to Sport Following Anterior Cruciate Ligament Reconstruction." Journal of Orthopaedic & Sports Physical Therapy 42, no. 9 (2012): 750–759.

5. Kotsifaki R, Van Rossom S, et al. "Aspetar Clinical Practice Guideline on Rehabilitation After Anterior Cruciate Ligament Reconstruction." British Journal of Sports Medicine 57, no. 9 (2023): 500–514.

6. Kotsifaki A, Whiteley R, Hansen C, et al. "Single Leg Hop for Distance Symmetry Masks Lower Limb Biomechanics: Time to Discuss Hop Testing Validity After ACL Reconstruction." British Journal of Sports Medicine 56, no. 5 (2022): 249–256.

7. Kotsifaki A, Whiteley R, Van Rossom S, et al. "Single Leg Vertical Jump Performance Identifies Knee Function Deficits at Return to Sport After ACL Reconstruction in Male Athletes." British Journal of Sports Medicine 56, no. 9 (2022): 490–498.

8. Kyritsis P, Bahr R, Landreau P, Miladi R, Witvrouw E. "Likelihood of ACL Graft Rupture: Not Meeting Six Clinical Discharge Criteria Before Return to Sport Is Associated with a Four Times Greater Risk of Rupture." British Journal of Sports Medicine 50, no. 15 (2016): 946–951.

9. McPherson AL, Feller JA, Hewett TE, Webster KE. "Psychological Readiness to Return to Sport Is Associated with Second Anterior Cruciate Ligament Injuries." American Journal of Sports Medicine 47, no. 4 (2019): 857–862.

10. Paterno MV, Thomas S, VanEtten KT, Schmitt LC. "Confidence, Ability to Meet Return to Sport Criteria, and Second ACL Injury Risk Associations After ACL-Reconstruction." Journal of Orthopaedic Research 40, no. 1 (2022): 182–190.

11. Losciale JM, Zdeb RM, Ledbetter L, Reiman MP, Sell TC. "The Association Between Passing Return-to-Sport Criteria and Second Anterior Cruciate Ligament Injury Risk: A Systematic Review with Meta-Analysis." Journal of Orthopaedic & Sports Physical Therapy 49, no. 2 (2019): 43–54.

This article is educational content and general information. It is not individual medical advice. For assessment and treatment specific to you, consult a qualified health professional.