In short: You're not ready on a certain date, but once you've met the criteria: usually no earlier than 9 months after surgery, strength symmetry to the healthy leg (LSI ≥ 90 %), a passed hop-test battery, clean landings without the knee giving way – and the confidence to trust your knee in a challenge. That last, psychological point is the one most often overlooked, and it's one of the strongest factors for a re-tear.
"When can I play again?" was my first question after every surgery. I wanted a date. Something I could write in the calendar. And that's exactly the trap almost everyone falls into.
After my second ACL tear, my knee was objectively stable after ten months – all tests passed, clearance given. Even so, my head sounded the alarm at the first sharp change of direction. That made one thing clear to me: "cleared" and "ready" are two different things. Your body can be far enough along that a physio gives the green light – and your head still lags weeks behind.
That's why the honest answer to "How do I know I'm ready?" isn't a number in the calendar, but a checklist that both your leg and your head have to pass.
Important upfront: This article is no substitute for medical advice. Clearance to return to sport is always made by your surgeon or physiotherapist based on your individual healing. The values mentioned here are for orientation, not for self-diagnosis.
At a glance
- Criteria, not calendar: It's not the date that decides, but whether you've met the test criteria. "Cleared" doesn't automatically mean "ready".
- Time as a lower limit: Usually no earlier than 9 months after surgery. Every month earlier measurably increases the re-rupture risk (Grindem et al.).
- Strength symmetry: Quadriceps strength side-to-side – target LSI ≥ 90 % relative to the healthy leg.
- Hop-test battery: Single-hop, triple-hop, crossover-hop, 6-metre timed hop – each at ≥ 90 % symmetry.
- No warning signs: No swelling, no giving-way (buckling) under load.
- Mental readiness: Trust in your knee during a challenge – the most commonly overlooked point.
Why criteria-based and not date-based?
A biological graft needs time to remodel – and this time can't be shortened by diligent training. That's why time on its own is a lower limit, not a goal. Studies (including Grindem et al., 2016) suggest that returning to sport before 9 months and without passing the test criteria significantly increases the risk of re-injury – every month earlier counts measurably against you.
The thinking error almost everyone makes: "The doctor cleared me, so I'm ready." Clearance means that from a medical point of view there's nothing more against loading your leg. You're only ready for full-contact challenges once your leg passes the tests and your head comes along. Both have to be right.
The criteria battery: your decision path
Instead of waiting for a date, you work your way through five stages. Only once one is met do you move on to the next.
- Time criterion (≥ 9 months): The biological lower limit. Coming back earlier means a higher re-rupture risk – no matter how good you feel.
- Measure strength symmetry (LSI ≥ 90 %): Your physio measures quadriceps strength on both sides. The Limb Symmetry Index (LSI) puts your operated leg in relation to the healthy one. Target: at least 90 %.
- Pass the hop-test battery: Four jump tests compared side-to-side – single-hop (single-leg long jump), triple-hop (three jumps in a row), crossover-hop (with a change of direction) and 6-metre timed hop (against the clock). Each individually at ≥ 90 % symmetry.
- Sport-specific loading & landing training: Agility, cutting, unexpected changes of direction, clean landings without the knee buckling. Here you train exactly the movements in which cruciate ligaments tear.
- Check mental readiness: Do you trust your knee in a challenge? Do you go into the situation without protecting yourself? This is the stage that no strength gauge captures.
The LSI and the hop tests – briefly explained
The Limb Symmetry Index is the ratio of your operated leg's performance to the healthy side, in percent. An LSI of 90 % means: your operated leg achieves 90 % of what the healthy one manages. An important catch that good physios know: if your "healthy" leg has also become weaker during the time off, the LSI can look too optimistic. That's why it's only one building block, not the whole picture.
The "when" table: criteria, not calendar
| Criterion | Target/timeframe | Condition |
|---|---|---|
| Time since surgery | usually ≥ 9 months | biological lower limit, non-negotiable |
| Quadriceps strength (LSI) | ≥ 90 % | measured side-to-side |
| Hop-test battery | each ≥ 90 % | all four tests passed |
| Swelling / effusion | none | symptom-free even after loading |
| Giving-way | none | no buckling under load |
| Mental readiness | trust in a challenge | be honest with yourself |
Psychological readiness – the overlooked factor
Here's the point that Dranbleiben is really about at its core: your head often lags behind your knee. You can pass every physical test and still not feel ready – because your nervous system has stored the moment of the tear.
In sports medicine this is measured with the ACL-RSI scale (Anterior Cruciate Ligament – Return to Sport after Injury). It captures your trust in your knee, your fear of re-injury and your emotional readiness. And the research is clear here: low psychological readiness is one of the strongest predictors of someone not returning to sport – and fear of re-injury is linked to a measurably increased risk of re-injury.
The important thing about this: that "I don't feel ready yet" is not a sign of weakness and no reason to push. It's information to be taken seriously. Many are physically cleared and still don't feel ready – that's normal. The right approach isn't to force yourself, but to gather the experience in controlled steps that your knee holds up. Confidence comes through experience, not through willpower.
When to see a doctor or physio
Warning signs: If you don't meet the criteria – LSI under 90 %, failed hop tests, recurring swelling – or if your knee buckles under load (giving-way), you don't belong back in full contact. Talk to your physio or surgeon before you return. A single challenge taken too early can undo months of rehab.
Frequently asked questions
When can I do sport again after an ACL tear? Not on a fixed date, but once you've met the criteria – usually no earlier than 9 months after surgery, combined with strength symmetry (LSI ≥ 90 %), a passed hop-test battery and mental readiness. An earlier return to sport measurably increases the re-rupture risk. The specific clearance is always made by your physio or surgeon. You'll find a compact return-to-sport checklist to tick off in the download area of Dranbleiben.
What is the LSI for the ACL? The Limb Symmetry Index (LSI) is the ratio of your operated leg's performance to the healthy leg, in percent. For return to sport, an LSI of at least 90 % in strength and jump tests is usually taken as a guide value. Important: if the healthy leg has also been weakened by the time off, the value can turn out too optimistic. The rehab roadmap in the download area of Dranbleiben shows you how to interpret the individual test values across your rehab.
Why isn't medical clearance alone enough? Because "cleared" and "ready" aren't the same thing. Clearance says there's nothing more against loading from a medical point of view – whether you really trust your knee in a challenge is a second, psychological question. It's exactly this point that often decides whether there's a re-tear. How to honestly assess your mental readiness is the core topic of the chapter "The path ahead" in Dranbleiben.
Is it normal not to feel ready despite passing the tests? Yes, and it should be taken seriously rather than glossed over. Very many are physically cleared and still feel hesitant at the decisive moment – the head often needs longer than the knee. That's no reason to hold back or force yourself, but a sign to build trust in small steps. You'll find exercises for this in the rehab community and in the download area of Dranbleiben.
Read more
- When can I go running again after an ACL tear? – the step before return to sport, with a realistic timeframe
- The fear of a second ACL tear – how to deal with the re-rupture fear that comes up during your comeback
Return to sport is the moment the whole rehab works towards – and it's precisely here that most protocols leave you alone with your head. In Dranbleiben I describe both sides of the comeback: the measurable criteria for your knee and the honest path to regaining confidence. You take the return-to-sport checklist from the download area straight to your next physio appointment, and in the rehab community you'll find people standing at exactly this point like you.