Three things to know about ACL injuries

Written by Dr Sean Leo, a consultant orthopaedic surgeon whose clinical focus is the knee, sports injuries and the lower limb.

Last updated: 9 October 2026.

Not every anterior cruciate ligament (ACL) tear needs surgery. ^[2] Some knees do well with structured rehabilitation, while others need more stability for work or for sport that involves cutting and pivoting. A torn ACL does not always mean the end of an active life. It does mean the knee needs a proper assessment.

What is the short answer on ACL tears and surgery?

Not every anterior cruciate ligament (ACL) tear needs surgery. ^[2] Some knees do well with structured rehabilitation, while others need more stability for work or for sport that involves cutting and pivoting. Results of reconstruction, an operation that replaces the torn ligament with a graft (a piece of tendon), are generally good, but they are not a promise ^[1], and recovery is judged by milestones rather than a date.

What does this page cover?

• Does every ACL tear need surgery?
• Can the knee compensate for a torn ACL?
• What can someone expect from ACL reconstruction?
• What should I do next?

Does every ACL tear need surgery?

No. Some people can regain useful function with structured rehabilitation and changes to activity. Others keep having episodes of giving way, or need stability for work or for sport that involves cutting and pivoting.

• A torn ACL does not always mean the end of an active life. It does mean the knee needs a proper assessment.
• Other injuries in the same knee, such as the meniscus, cartilage or another ligament, can change the decision.
• Advice for a newly injured knee should not be applied automatically to someone who has had giving way for a long time.

More on what rehabilitation-led care involves

Rehabilitation-led care is not “doing nothing”. It usually involves progressive work on swelling, motion, strength, balance, movement control and a graded return to the activities that matter to you. The response is reviewed along the way. If the knee keeps giving way, or important work or sport demands cannot be met, reconstruction may be reconsidered.

Owner clinical review required · not a release asset

Can the knee compensate for a torn ACL?

Sometimes, to a degree. When the injury involves only the ACL, the muscles around the knee may partly stabilise it. That is a possibility, not a guarantee, and it differs from one knee to the next.

• Some torn knees stay steady for everyday activity, while others repeatedly give way during sport, work or ordinary turning.
• A knee that copes for daily life may still not cope with cutting or pivoting.

More on what the ACL does

The ACL is one of the major ligaments inside the knee. It helps control forward and rotational movement of the shin bone relative to the thigh bone, particularly in landing, cutting and pivoting.

What can someone expect from ACL reconstruction?

Reconstruction is considered when the knee has persistent instability or repeated giving way, when someone wants to return to demanding cutting or pivoting activity, or when other injuries change the balance of the decision. Results are generally good but that is not a promise for any one knee. ^[1]

• Not every athlete needs reconstruction, and age alone does not decide the treatment.
• Repair of the ligament, rather than reconstruction, is a selective option for some tears, and its longer-term evidence is limited.
• The ACL pillar page sets out the options side by side, and the decision is made after an assessment.

How is recovery after reconstruction judged?

Recovery after reconstruction is better described as overlapping phases than as a guaranteed calendar. Progress is judged by milestones as well as time, and the calendar alone is not clearance to return to sport.

• Progress can pause or move backwards if symptoms increase or a milestone is not met.
• Associated injuries can change how quickly each stage is reached.

When should a knee injury be checked urgently?

What should I do next?

If you have hurt your knee, or have been told you have a torn ACL, an assessment is a sensible next step. It brings together what happened, an examination and any tests that help, so that you and your clinician can decide what to do next. An appointment supports an informed decision. It is not a commitment to surgery.

• Read how an ACL injury is assessed and how the treatment options compare on the ACL reconstruction surgery page.
• For a fuller look at ACL injuries, read the comprehensive guide to ACL injuries, treatment and recovery.
• Browse the Knee Hub or the Knowledge Centre for other knee problems.
• Read about ACL tear symptoms.
• Read about whether a torn ACL can heal without surgery.
• Read about who is suitable for ACL repair.
• Read about MCL tear symptoms and grades.

References

1. Samitier G, Marcano AI, Alentorn-Geli E, Cugat R, Farmer KW, Moser MW. Failure of Anterior Cruciate Ligament Reconstruction. Arch Bone Jt Surg. 2015;3(4):220-240. PMID:26550585. PMCID:PMC4628627.
2. Frobell RB, Roos HP, Roos EM, Roemer FW, Ranstam J, Lohmander LS. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346:f232. doi:10.1136/bmj.f232. PMID:23349407. PMCID:PMC3553934.