Most people should wait at least NINE months after ACL surgery before going back to cutting, pivoting or contact sport, and only after passing strength and hop tests.
Both parts matter. For every month you wait up to nine months, the chance of injuring the knee again roughly halves. People who pass a full set of tests have far fewer re-injuries than people who don’t.
The date on the calendar is not the green light. Your results are.
What the numbers show
- Going back before nine months: about 4 in 10 re-injured the knee in one well-known study
- Going back after nine months: about 2 in 10
- Passing every test before going back: about 1 in 20 re-injured
- Failing one or more tests: nearly 4 in 10
- After nine months, waiting longer didn’t add much extra protection. Passing the tests did
Nine months is the minimum. Passing the tests is the permission.
The tests
- Thigh strength: your operated leg at 90 percent or more of the other one, measured on a machine, not guessed
- Hop tests: single hop for distance, triple hop, crossover hop and a timed hop, each at 90 percent or more of the other leg
- Knee questionnaires: how your knee feels and works in daily life and sport
- No swelling after sport-type training, full movement and good landing control
The catch with “90 percent of the other leg”
- Your GOOD leg has also lost strength after a year of less training. So 90 percent of a weaker leg can flatter you
- In one study, most people who passed the 90 percent test were still well short of where they’d been before the injury, and most of the later re-injuries happened in that group
- If you have strength numbers from before the injury, use those as the target. If not, treat 90 percent as the floor, not the finish line
Feeling ready too early
- Confidence is usually treated as a good sign. But in one study, people who felt VERY confident at three months had more second injuries than those who felt less sure
- The likely reason: confident people do more, in exactly the window when the new ligament is weakest
- Feeling ready at month three isn’t a green light. See ACL recovery month by month
The other knee
- Around 1 in 7 people have a second ACL injury, split roughly evenly between the new graft and the OTHER knee
- Under 25 and back to sport: closer to 1 in 4
- In teenagers followed for ten years, about 1 in 3 injured the other knee. Over time, the other knee became the bigger risk
- So train both legs. Landing, cutting and strength work are for the whole body, not just the operated side
Will I get back to my old level?
- About 8 in 10 get back to some sport
- About 2 in 3 get back to the level they played at before
- About half get back to competitive sport
- Better odds go with being younger, being confident at the RIGHT time, and good strength and hop results
Passing the tests lowers the risk. It doesn’t remove it.
Not every sore knee on the way back is the graft. Pain around the kneecap, or on the outside of the knee as running builds up, is often runner’s knee or IT band syndrome, and both usually settle with changes to training load.
Get checked before going back if
- The knee swells after training
- It gives way, catches or locks
- You haven’t had formal strength and hop testing
- You can’t fully straighten it, or it doesn’t bend as far as the other knee
Wait for nine months, then earn it with the tests. And train both legs, because the other knee is at risk too.