ACL Reconstruction Timeline Calculator
Return-to-sport protocol milestones after ACL surgery.
About this calculator
Beischer et al. (Journal of Orthopaedic & Sports Physical Therapy, 2020;50(2):83-90) found that young athletes who returned to sport before 9 months after ACL reconstruction had roughly seven times the rate of a second ACL injury compared with those who waited longer -- building on earlier work by Grindem et al. (British Journal of Sports Medicine, 2016), which found each additional month rehabilitation was delayed, up to 9 months, was associated with roughly a 51% reduction in reinjury rate. Consensus rehabilitation guidance (van Melick et al., British Journal of Sports Medicine 2016) built on findings like these to establish 9 months as a minimum, criteria-based floor for return to competitive sport rather than a fixed calendar target -- which is why this calculator enforces 36 weeks as an absolute minimum for Return to Sport regardless of how favorable the other inputs are. Getting there faster is not necessarily better: graft-to-bone healing and neuromuscular control both take time to mature, and readiness is increasingly assessed by objective criteria rather than time alone -- commonly a quadriceps strength limb symmetry index (LSI) and a battery of single-leg hop tests, each compared against the uninjured leg, with 90% LSI a commonly cited passing threshold (routinely raised to 90% specifically for higher sport-demand athletes here, since a stricter standard is generally warranted before returning to cutting and pivoting sports).
Several factors extend the published timeline further: allograft tissue incorporates into bone more slowly than autograft, a concomitant meniscus repair restricts early weight-bearing and knee flexion to protect the repair, revision surgery (a repeat reconstruction) generally requires more cautious progression, and older patients tend to need more time for the same biological healing. Estimated re-tear risk is shown alongside the timeline because it is not zero at any point -- it is elevated for allograft tissue, for younger athletes returning to high-demand cutting or pivoting sports, and for revision surgery, which is worth weighing against the temptation to accelerate the published timeline. Pre-injury Tegner score is recorded for the case file only -- the rehab timeline, re-tear risk, and LSI targets are driven entirely by graft type, meniscus repair, patient age, sport demand level, and revision status, so a patient's prior activity level plays no role in the numbers this calculator produces.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Return to sport (weeks)
36
Figures current as of 2020. Sources: Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after anterior cruciate ligament reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016. doi:10.1136/bjsports-2016-096031, Beischer S, Gustavsson L, Senorski EH, Karlsson J, Thomeé C, Samuelsson K, Thomeé R. Young athletes who return to sport before 9 months after anterior cruciate ligament reconstruction have a rate of new injury 7 times that of those who delay return. J Orthop Sports Phys Ther. 2020;50(2):83-90.
How to Use This Calculator
- Select the Graft type used in surgery: BPTB autograft, hamstring autograft, quadriceps tendon, or allograft.
- Indicate whether a Meniscus repair was performed simultaneously (No or Yes) — this extends early restrictions.
- Enter the patient's Age in years and Sport demand level (Sedentary through Elite/competitive).
- Enter the Pre-injury Tegner score (0–10) for the case record, and select whether this is a Revision surgery.
- Review the milestone timeline including jogging clearance (weeks), return-to-sport (weeks and months), and estimated graft re-tear risk (%).
What each input means
- Graft type
- Graft source used for the reconstruction.
- Meniscus repair?
- Meniscus repair restricts early weight-bearing and flexion.
- Patient age (years)
- Age in years. Younger patients heal faster but have higher re-tear rates.
- Sport demand level
- Sport demand level to return to.
- Pre-injury Tegner score (0-10)
- Tegner activity level scale (10=competitive sports, 0=sick leave), recorded for the case record. This calculator's rehab timeline is driven by graft type, meniscus repair, age, sport demand, and revision status rather than the pre-injury Tegner score.
- Revision surgery?
- Revision surgery requires longer rehab.
What each result means
- Return to sport (weeks)
- Estimated earliest return to full competitive sport.
- Return to sport (months)
- Same milestone in months.
- Full extension (week)
- Target week for achieving full knee extension (0°).
- Full weight-bearing (week)
- Expected week for walking without crutches.
- Jogging cleared (week)
- Earliest week for straight-line jogging.
- Agility drills (week)
- Earliest week for lateral movement and agility drills.
- Full practice (week)
- Earliest week for full sport-specific practice.
- Re-tear risk (%)
- Estimated graft re-tear risk based on patient profile.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersGraft type = 0, Meniscus repair? = 0, Patient age (years) = 28, Sport demand level = 3 = 6 input(s) provided
- Calculate Return to sportReturn to sport36 = 36
- Calculate Return to sportReturn to sport8.3 = 8.3
- Calculate Full extensionFull extension2 = 2
Figures and sources
- ACL reconstruction return-to-sport reinjury-risk timing (Delaware-Oslo cohort) (2016) — Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after anterior cruciate ligament reconstruction: the Delaware-Oslo ACL cohort study. Br J Sports Med. 2016. doi:10.1136/bjsports-2016-096031
- 9-month minimum floor for ACL return-to-sport (2020) — Beischer S, Gustavsson L, Senorski EH, Karlsson J, Thomeé C, Samuelsson K, Thomeé R. Young athletes who return to sport before 9 months after anterior cruciate ligament reconstruction have a rate of new injury 7 times that of those who delay return. J Orthop Sports Phys Ther. 2020;50(2):83-90.
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why is 9 months (36 weeks) treated as a hard floor for return to sport, not just a typical timeline?
A widely cited 2020 study (Beischer et al., JOSPT) found that athletes who returned to sport before 9 months post-reconstruction had roughly seven times the rate of a subsequent ACL injury compared with those who waited longer, echoing earlier work (Grindem et al., 2016) linking each month of delay up to 9 months with roughly a 51% lower reinjury rate -- and consensus rehabilitation guidelines built on evidence like this since treat 9 months as a minimum floor rather than an average -- regardless of how well an individual patient's strength and hop testing look earlier than that, tissue healing and neuromuscular retraining are not considered complete enough to safely resume cutting and pivoting sport before then.
Why does allograft tissue take longer to clear for return to sport than an autograft?
An allograft (donor tissue) generally incorporates into the surrounding bone tunnels more slowly than an autograft (the patient's own tendon), because it does not carry the same living cell population that speeds early biological remodeling -- which is why this calculator adds extra time to jogging clearance, agility drills, full practice, and return to sport specifically for allograft cases.
Why does a meniscus repair performed at the same time as ACL reconstruction slow down the whole timeline?
A meniscus repair needs protection from excessive load and deep knee flexion while its own healing matures, which is a more restrictive early rehabilitation phase than ACL reconstruction alone typically requires -- so when both are performed together, the more conservative meniscus-repair restrictions govern early weight-bearing and range of motion, and that caution carries forward into later milestones as well.
What do the Quad LSI Target and Hop LSI Target numbers mean?
Both compare strength or hop-distance performance on the surgical leg against the uninjured leg as a percentage (limb symmetry index, LSI) -- a 90% target means the surgical leg needs to reach at least 90% of the uninjured leg's performance before that criterion is considered met. This calculator sets a stricter 90% target for higher sport-demand levels (cutting/pivoting and elite/competitive) and a somewhat more lenient 85% for lower-demand return-to-activity goals.
Is re-tear risk the same for every patient regardless of graft type or age?
No -- this calculator's estimated re-tear risk starts from a baseline for autograft reconstruction and adds to it for allograft tissue (which carries a higher published failure rate), for younger athletes (who return to higher-demand activity more often and for longer), for higher sport-demand levels, and for revision surgery, since a second reconstruction generally carries a higher risk of a further failure than a first-time primary reconstruction.
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