What is acl injury?
The anterior cruciate ligament (ACL) runs through the centre of the knee and stops the shin bone sliding forwards. It is most often torn during sports involving sudden pivots, landings or changes of direction, such as football, netball, rugby and skiing. Many people hear or feel a pop, the knee swells within hours, and afterwards it may give way during twisting movements. ACL injuries are most common in active people in their teens, twenties and thirties, and are proportionally more frequent in women playing pivoting sports.
A specialist can usually diagnose an ACL tear from the history and examination, using tests that check how the knee moves. An MRI scan confirms the tear and shows any associated damage to the meniscus or other ligaments, which is common.
Common symptoms
- A pop felt or heard at the moment of injury
- Rapid swelling within a few hours
- Pain and difficulty continuing activity
- The knee giving way on twisting or turning
- A feeling of instability or not trusting the knee
- Restricted movement in the early days after injury
How long will you wait?
After a routine NHS referral, seeing a knee specialist, obtaining an MRI and reaching ACL reconstruction commonly spans several months, and around a third of patients on NHS waiting lists currently wait over 18 weeks for treatment.
Privately, you can typically see a knee surgeon within 3–7 days, have an MRI within days of that, and undergo reconstruction within 2–6 weeks once swelling and movement allow.
NHS England median referral-to-treatment wait: 12.4 weeks, with 2.5 million people waiting over 18 weeks (May 2026). Individual waits vary by trust and urgency.
Treatment options
- Structured rehabilitation. Progressive physiotherapy rebuilds strength and control, and some people return to their chosen activities without surgery.
- ACL reconstruction. Keyhole surgery replaces the torn ligament with a graft, usually from your hamstring or patellar tendon, restoring stability for pivoting sports.
- Treatment of associated injuries. Meniscus tears or cartilage damage found alongside the ACL tear are often repaired during the same operation.
- Bracing and activity modification. For less active people, adapting activities and occasionally using a brace can manage instability without surgery.
What does private treatment cost?
As a guide, self-pay ACL reconstruction in the UK typically costs around £7,000–£9,500, depending on graft choice and any meniscal work needed at the same time.
Does health insurance cover acl injury?
A new ACL tear is exactly the kind of acute injury private medical insurance is designed for, and consultations, MRI, surgery and post-operative physiotherapy are normally covered. If you injured the knee before taking out the policy, treatment for that knee will usually be excluded as pre-existing. Check your policy's physiotherapy limits, as ACL rehabilitation runs for many months.
Frequently asked questions
Does a torn ACL always need surgery?
No. The decision depends on your age, activities and how unstable the knee feels. People who want to return to pivoting sports usually benefit from reconstruction, while those with less twisting demand on the knee can often do well with dedicated rehabilitation alone. A specialist can help you weigh up both routes.
How long before I can play sport again after ACL reconstruction?
Return to pivoting sport typically takes nine to twelve months. Although the knee often feels good earlier, the graft and the muscles protecting it need time to mature and strengthen, and returning too soon raises the risk of re-injury. Most surgeons use strength and hop testing rather than the calendar alone to guide the decision.
What happens if I leave an ACL tear untreated?
Some knees cope well, particularly with good muscle strength and sensible activity choices. Others give way repeatedly, and each episode of instability risks further damage to the meniscus and joint surface, which is linked to earlier arthritis. If your knee keeps giving way despite rehabilitation, it is worth discussing reconstruction with a specialist.
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