ACL tear: do you need surgery, and where does PRP fit?
Reviewed by The Wellness Team. Last reviewed October 2026.
Short answer: an ACL (anterior cruciate ligament) tear is a common sporting knee injury. NHS trust guidance says the body cannot repair a fully ruptured ACL, but not everyone with a rupture needs reconstructive surgery. Many people do well with structured physiotherapy. PRP does not mend a ruptured ACL, and we would not suggest it for that.
What an ACL injury feels like
An East Kent Hospitals NHS Foundation Trust leaflet describes the usual story: a twist of the knee, a sudden stop or change of direction, or a collision during sport. The knee swells, is painful and is hard to move or walk on. Once the pain settles, the knee can feel unstable or give way.
NHS Bexley MSK service adds that people often report a pop at the time of injury, with swelling within about 2 hours, and sometimes cannot continue playing or put weight on the leg.
Do you always need surgery?
No. The East Kent NHS leaflet says some people with a ruptured ACL do not get giving way or instability, or are happy to change their activities, or have not damaged other parts of the knee. It says the decision should be made jointly with your surgeon, knee specialist and physiotherapist.
NHS Bexley MSK describes a high-quality trial that compared surgery with non-surgical treatment and found no difference in pain, symptoms, function in sport and recreation, or return to pre-injury activity between the groups. It also notes that, for those who do need surgery, a period of rehabilitation before the operation may improve results.
What to do in the first days
East Kent NHS advises cutting down activity for the first few days, using pain relief or a knee support, and using ice if the knee is swollen. Unless a surgeon or knee specialist tells you otherwise, you can usually walk with full weight through the leg. Crutches or a brace may be given if you struggle to walk.
Get the knee assessed after any injury where it swelled quickly, gave way, locked or would not take your weight. NHS advice for a very painful or badly swollen knee, or one you cannot move or put weight on, is to call 111.
Where PRP fits
Platelet-rich plasma (PRP) is made from a small sample of your own blood. It is not a treatment for a fully torn ACL, and no injection replaces the ligament. Where we can help is with the knee around an old injury: for example, a painful joint or tendon that has not settled after rehabilitation, once the cause has been properly assessed. The research is mixed and results vary. We do not guarantee an outcome.
Our prices are plain: PRP for a joint is £750.
Next step
If you have had an ACL injury and the knee is still sore, we can talk through your history and tell you honestly whether an injection makes sense or whether rehabilitation or an orthopaedic opinion should come first.
Message us on WhatsApp or read our knee injection guide.
Sources: East Kent Hospitals NHS Foundation Trust, Anterior cruciate ligament (ACL) injury patient leaflet (leaflets.ekhuft.nhs.uk); NHS Bexley MSK, Anterior cruciate ligament (ACL) injury (msk-bexley.nhs.uk). This article is general information and not a diagnosis.