--- title: "Back to sport after an ACL: what strength testing shows" id: "8522" type: "post" slug: "acl-return-to-sport-testing" published_at: "2026-10-11T07:42:33+00:00" modified_at: "2026-10-11T07:42:33+00:00" url: "https://www.allforone.com.au/acl-return-to-sport-testing/" markdown_url: "https://www.allforone.com.au/acl-return-to-sport-testing.md" excerpt: "When can you play again after an ACL reconstruction? What the research says about timing and strength, and how VALD testing compares your two legs." taxonomy_category: - "All in" --- Physio · 7 minute read After an ACL reconstruction, the date you go back to sport matters less than whether your leg is ready. Strength testing measures that by comparing the operated leg with the other one in force, jumping and landing. ### The short version - A large review found 81% of people played some sport again after ACL surgery, but only 55% got back to competitive sport. - In a Melbourne study of people who had surgery before age 20, 35% went on to injure an ACL again, either the graft or the other knee. - Waiting longer (up to about 9 months) and getting the quads closer to even were both linked with fewer reinjuries. Most people coming back from an ACL reconstruction ask their physio the same thing: when can I play? Time since surgery is part of the answer. The rest depends on how strong the operated leg is, how well it absorbs a landing, and how it compares with the other side. You can’t judge those by feel, because a knee can feel fine long before the muscles around it have caught up. ## ACL injuries and reinjuries in numbers ACL reconstructions are becoming more common in Australia. Over 15 years, the yearly rate rose by 43%, and by 74% in people under 25, according to an Australian study. The people most at risk were men aged 20 to 24 and women aged 15 to 19. Surgery is only the start. A review of 69 studies found 81% of people returned to some kind of sport, 65% got back to their previous level, and 55% returned to competitive sport. A second injury is the bigger worry. Researchers at a Melbourne knee clinic followed patients who had their ACL reconstructed before age 20. Over about five years, 35% had another ACL injury, split almost equally between the new graft and the other knee. ## Time, strength and reinjury Two findings come up again and again. The first is time. In the Delaware-Oslo study, which followed people in Norway after ACL surgery, each month they waited cut the reinjury rate by 51%, up to about 9 months after the operation. After that, waiting longer made little difference. The second is strength, in particular the quadriceps at the front of the thigh. The same study found that more even quad strength between the legs before returning was linked with fewer reinjuries. People who returned without passing the study’s tests reinjured their knee far more often (38%) than those who passed (under 6%), though the group was small enough that this gap fell just short of statistical certainty. A study of 158 male professional athletes found something similar. Those who went back without meeting all six discharge tests were four times as likely to rupture the new graft, and weaker hamstrings compared with the quads was also linked to rupture. These were elite players, so the exact figure may not apply to recreational players. [Book at Yarraville](https://momence.com/appointments/appointment-reservation/37352?boardId=14183&serviceId=324079&venueId=21391) [Book at Hampton East](https://momence.com/appointments/appointment-reservation/37352?boardId=14785&serviceId=324079&venueId=22183) ## What a strength test measures We use VALD force plates and a VALD ForceFrame at our Yarraville and Hampton East studios. The force plates read how much force each leg makes as you jump, land and hop, and how quickly it makes it. The ForceFrame isolates single muscle groups, so your physio can compare your left quads with your right, and your hamstrings against your quads. The result is shown as a percentage. If your operated leg produces 85% of the force of your other leg, the gap is 15%. Many physios look for that gap to be within about 10% before a return to sport, alongside the hop tests, time since surgery and how confident you feel in the knee. ## Why one test isn’t enough Comparing one leg with the other has a catch. After surgery, the good leg loses some strength too, because you have been doing less on it. That can make the operated leg look closer to normal than it is. One study found 57% of people passed when their operated leg was compared with the other leg, but only 29% passed when it was compared with what both legs could do before the injury. Hop tests can also hide differences. In one study of male athletes who had been cleared to play, hop distance and strength looked even between the legs, yet the operated leg jumped clearly lower in a vertical jump. That’s why your physio will look at several measures together, and why a retest every few weeks during rehab tells you more than one test at the end. ## Who makes the call An international consensus on return to sport describes it as a gradual process that runs alongside rehab, ideally decided together by you, your physio and, where there is one, your coach. Strength testing doesn’t make the decision. It gives you all the same numbers to look at. If you’re still in rehab with us, your [physiotherapist](https://www.allforone.com.au/treatment/physiotherapy/) can build the testing into your plan. ## Getting tested 1. 1**Book in, no referral needed**Strength testing is a 40-minute physiotherapy appointment, claimable on private health extras. 2. 2**Bring your surgery details**Tell us the date of your operation and what your surgeon has said about returning to sport. 3. 3**Do the tests**Your physio picks tests that suit where you are in rehab, from strength checks early on to jumps and hops later. 4. 4**Go through your report**You’ll see each measure for both legs, the gap between them, and what to work on next. 5. 5**Retest**Your physio will suggest when to come back so you can see the gap closing. ## The takeaway After an ACL reconstruction, enough time and even strength between your legs are both linked with fewer reinjuries. Strength testing measures the second one, so you and your physio can decide on your return based on what your leg can do. ### Worth checking with your physio or surgeon before you return if - Your knee still swells after training - You avoid landing or turning on the operated leg - It’s been less than 9 months since your surgery - You haven’t had your strength compared between legs Find out where your knee is at A [strength test](https://www.allforone.com.au/treatment/strength-testing/) is 40 minutes with one of our physios at Yarraville or Hampton East. You’ll get each leg’s numbers, the gap between them, and clear next steps for your rehab. [Book at Yarraville](https://momence.com/appointments/appointment-reservation/37352?boardId=14183&serviceId=324079&venueId=21391) [Book at Hampton East](https://momence.com/appointments/appointment-reservation/37352?boardId=14785&serviceId=324079&venueId=22183) ## Common questions ### When can I return to sport after an ACL reconstruction? It depends on your knee, your sport and your surgeon’s advice. Research links waiting until about 9 months after surgery, and having even strength between your legs, with fewer reinjuries. Your physio and surgeon will look at both. ### What is a limb symmetry index? It’s the operated leg’s result shown as a percentage of the other leg’s. A result of 90% means the operated leg produced 90% of what the other leg did. Many physios look for 90% or more before a return to sport. ### Can I do strength testing while I’m still in rehab? Yes. Early on your physio will test strength in positions that suit your stage of recovery, then add jumps and hops when you’re ready. Regular retests show how your rehab is going. ### Do I need a referral? No. It’s a physiotherapy appointment, so you can book without a referral and claim it on private health extras. ### Is strength testing only for athletes? No. Anyone returning to running, netball, footy, skiing or any other sport after a knee injury can be tested. ### Where can I get ACL strength testing in Melbourne? We test at our Yarraville studio in the inner west and our Hampton East studio in the bayside south east, using VALD force plates and the ForceFrame. ### Keep reading - [What a strength test measures and why it matters](https://www.allforone.com.au/what-a-strength-assessment-measures/) - [Understanding ACL injuries in women](https://www.allforone.com.au/physiotherapy-acl-injuries-women/) - [Physiotherapy for knee injuries](https://www.allforone.com.au/physiotherapy-for-knee-injuries/) **General information only.** This article is general information, not advice for your situation. Every knee and every surgery is different, so follow your surgeon’s and physio’s advice about when and how to return to sport. ### Sources - Zbrojkiewicz D and others. [Increasing rates of anterior cruciate ligament reconstruction in young Australians, 2000-2015](https://pubmed.ncbi.nlm.nih.gov/29669497/) . Medical Journal of Australia, 2018. - Ardern CL and others. [Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors](https://pubmed.ncbi.nlm.nih.gov/25157180/) . British Journal of Sports Medicine, 2014. - Webster KE, Feller JA. [Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction](https://pubmed.ncbi.nlm.nih.gov/27390346/) . American Journal of Sports Medicine, 2016. - Grindem H and others. [Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study](https://pubmed.ncbi.nlm.nih.gov/27162233/) . British Journal of Sports Medicine, 2016. - Kyritsis P and others. [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](https://pubmed.ncbi.nlm.nih.gov/27215935/) . British Journal of Sports Medicine, 2016. - Wellsandt E and others. [Limb symmetry indexes can overestimate knee function after anterior cruciate ligament injury](https://pubmed.ncbi.nlm.nih.gov/28355978/) . Journal of Orthopaedic and Sports Physical Therapy, 2017. - Kotsifaki A and others. [Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes](https://pubmed.ncbi.nlm.nih.gov/35135826/) . British Journal of Sports Medicine, 2022. - Ardern CL and others. [2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern](https://pubmed.ncbi.nlm.nih.gov/27226389/) . British Journal of Sports Medicine, 2016. - O’Malley E and others. [Countermovement jump and isokinetic dynamometry as measures of rehabilitation status after anterior cruciate ligament reconstruction](https://pubmed.ncbi.nlm.nih.gov/30109947/) . Journal of Athletic Training, 2018.