A kneecap (patellar) dislocation happens when the kneecap slips out of its groove at the front of the knee, almost always towards the outside. It usually occurs during a twist or change of direction with the foot planted, and it is most common in teenagers and young adults. A first dislocation is normally treated with a short period of support followed by rehabilitation, but some people go on to have repeated dislocations and may need surgery.
Also known as patellar dislocation, patellofemoral instability, dislocated kneecap, patellar subluxation
Anatomy: where the problem is
Front view of the knee. Highlighted in the diagram: kneecap (patella) and inner kneecap ligament.
Symptoms
- A sudden feeling of the knee giving way, with the kneecap visibly out of place
- Severe pain and rapid swelling
- A pop at the time of injury
- The kneecap often slips back as the knee is straightened
- Afterwards: tenderness on the inner side of the kneecap, and a feeling that it might slip again
- Apprehension when the knee is bent and the kneecap is pushed outwards
Causes and risk factors
- A twisting movement or change of direction with the foot planted
- A direct blow to the kneecap
- A shallow groove at the end of the thigh bone, or a kneecap that sits high
- Joint hypermobility
- A previous dislocation
- A family history of kneecap instability
What the evidence says helps
- After a first dislocation, most people do not have another. In a large study, about 1 in 6 had a further dislocation over the following two to five years.1
- The risk is much higher once it has happened more than once: about half of people with a previous history went on to have further episodes.1
- A first dislocation is usually treated without surgery: a short period in a brace or splint, then exercises to restore movement and strengthen the thigh and hip muscles.2
- A Cochrane review found the evidence too low in quality to be sure whether surgery or rehabilitation is better after a first dislocation, although surgery may lower the chance of it happening again.2
- Surgery is more often advised for repeated dislocations, or when a fragment of bone or cartilage has been knocked off.2
Things you can try at home
- If the kneecap is still out of place, do not try to force it back: call 999 or go to A&E
- After a dislocation, get the knee assessed even if the kneecap has gone back in
- Use ice and keep the leg raised to reduce swelling in the first few days
- Follow advice on bracing and crutches, and start gentle thigh muscle exercises early
- Strengthen the thigh, hip and trunk muscles, and practise balance and landing control
- Return to twisting and jumping sports only when strength and confidence are restored
When to get urgent help
Contact your GP urgently, call NHS 111, or call 999 in an emergency if you have:
- A kneecap that is out of place and will not go back: call 999 or go to A&E
- A knee that swells rapidly after an injury: go to a minor injuries unit or A&E
- A knee that is locked or catches painfully after a dislocation: get same-day medical advice
- Numbness, tingling or a cold, pale foot after a knee injury: go to A&E
- A hot, swollen, tender calf with breathlessness: call 999
How Apollo can help
After a dislocation has been assessed medically, we guide rehabilitation through its stages: settling swelling, restoring movement, rebuilding strength in the thigh, hip and trunk, and retraining balance, landing and cutting. We test strength and control with our VALD equipment before return to sport. We also assess the factors that raise the risk of recurrence, and if the kneecap keeps slipping we write to your GP about a specialist opinion.
No GP referral needed. Clinics in Sheringham, Coltishall and Norwich.
Related reading
Frequently asked questions
Will my kneecap dislocate again?
Most people who have a first dislocation do not have another. The risk is higher in younger people, in those with joint hypermobility or a shallow groove, and it rises sharply after a second episode.
How long is recovery after a kneecap dislocation?
Most people are walking normally within a few weeks and return to sport in around three months, provided strength and control have been restored. It takes longer if cartilage or bone was damaged.
Do I need surgery after a dislocated kneecap?
Usually not after a first dislocation, unless a fragment of bone or cartilage has been knocked loose. Surgery to stabilise the kneecap is more often recommended when dislocations keep happening despite good rehabilitation.
References
- Fithian DC, et al. (2004). Epidemiology and Natural History of Acute Patellar Dislocation. The American Journal of Sports Medicine 32:1114-1121. View source
- Smith TO, Donell S, Song F, Hing CB (2015). Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database of Systematic Reviews. View source
This page is general information, not a diagnosis or a substitute for medical advice. If you are worried about your symptoms, speak to your GP or a registered healthcare professional. Content prepared from the sources above, November 2026.
