Dislocated kneecap: what to do, exercises, and stopping it happening again
A dislocated kneecap slides out of its groove to the outside of the knee, often from a twist on a planted foot, and usually pops back by itself. Even if it does, get it checked: an X-ray looks for a piece of bone or cartilage knocked off.
Most first dislocations are treated without surgery, with exercises that start straight away. About 1 in 3 people dislocate again, more often teenagers and people with a shallow groove or a high-riding kneecap. This guide covers what to do now, what trials found about surgery and braces, and a staged plan from the first days to sport.
Exercise is for pain that has been checked or is clearly mild and settling.
Get urgent medical help if
Go to A&E: you've injured your knee and it has changed shape, becomes very swollen very quickly, you felt a pop or snap, bone is sticking out, or it's bleeding heavily. Call 999 if you can't get to A&E because the pain stops you moving your leg. Don't drive yourself. While you wait, keep the knee still and supported with padding, and don't raise it, stand or walk on it, or try to put the kneecap back yourself.
Same day (NHS 111): you've injured your knee and it's very painful, swollen or bruised, you can't stand up or move your knee, or you think your kneecap dislocated and then moved back into place.
The knee is locked and you cannot fully straighten it.
A hot, red or swollen knee with sudden severe pain, a very high temperature, or feeling hot, cold or shivery. This can be a joint infection.
Leg pain or swelling with breathlessness or chest pain: call 999 or go to A&E, and do not drive yourself. It can be a blood clot that has reached the lungs.
See a doctor or physiotherapist if
The kneecap slips out again, or keeps feeling as if it will: ask for a specialist assessment. Repeat dislocations are common, and a second one is when surgery is usually discussed.
Swelling that keeps coming back, or painful catching or clicking: a loose piece of bone or cartilage needs checking.
You're not walking normally, or the knee won't straighten fully, by about 2 weeks.
A teenager with loose joints, or more than one dislocation: ask about a specialist review.
Understand it
What happensStrong evidence
The kneecap (patella) normally glides in a groove at the end of the thigh bone. In a dislocation it comes out of the groove, nearly always to the outside, and the tissues around it are torn or stretched. It usually happens with a sudden change of direction on a planted foot, sometimes with a blow: the knee bends from straight while it twists and falls inwards.
The ligament that holds the inner side of the kneecap (the medial patellofemoral ligament) is usually torn. The kneecap is least well held early in knee bend, which is why single-leg landing and cutting are the moves that need retraining.
In a 21-year population study of 609 people, about 23 in every 100,000 dislocated a kneecap for the first time each year, similar in males and females, and most often at 14 to 18 years (about 148 in 100,000). Loose (hypermobile) joints and a shallow or uneven groove make it more likely to keep happening; our guide to exercise with hypermobility covers loose joints.
The knee usually looks out of place or at an odd angle. The kneecap often pops back by itself, but it still needs checking: an X-ray makes sure the bones are in the right place and that no piece of bone or cartilage has been knocked off. In the population study, 2.3% needed surgery for that kind of bone-and-cartilage injury.
A pop with fast swelling and the knee giving way can also be an anterior cruciate ligament (ACL) injury, which has its own guide. The two can be hard to tell apart without an examination.
About 1 in 3 people dislocate again after a first dislocation: 33.6% across 17 studies, and 31% across 25 studies of non-surgical care. In a group of 189 people followed for 2 to 5 years, further instability happened in 17% of first-time dislocators and 49% of those who'd had problems before. In the population study, about 1 in 10 later had surgery for repeated dislocation. As nidirect puts it, most people won't dislocate it again, but in some people it keeps happening.
The risk is higher with younger age (about 2.6 times the odds), open growth plates (2.7), a shallow groove (trochlear dysplasia, 4.2), a tendon attachment that sits further out than usual (2.9) and a high-riding kneecap (patella alta, 2.4). With none of these, 8 to 14% dislocated again; with three, 70 to 79%. Sex wasn't a clear risk factor in that review, though girls had the highest risk in one older study. Only a specialist assessment, usually with a scan, can tell you which apply.
Many people walk as soon as they're treated, but the NHS says it can take several months to recover fully. The soft tissues usually take about 6 weeks to heal, and sport takes at least 6 to 8 weeks. In 160 teenagers treated without surgery, nearly half (47.5%) took more than 6 months to get back to sport; weaker thigh muscles, ongoing worry that the kneecap would slip and poorer stability scores went with a slower return.
Surgery after a first dislocation: an uncertain benefitMixed evidence
Most first dislocations are treated without surgery. A 2023 Cochrane review of 10 trials (519 people) found surgery might lower the chance of another dislocation: if about 35 in 100 dislocate again without surgery, about 19 in 100 would after surgery, over 2 to 9 years. But the evidence was very low certainty, knee function scores weren't clearly better (about 6 points on a 100-point scale, where 10 is the change people notice), and side effects were uncertain. An earlier Cochrane review found a less certain benefit at 6 to 9 years.
The NHS says surgery may be needed if the knee is badly damaged or the kneecap has dislocated more than once. No good trial has looked at people who keep dislocating, which is when specialists usually discuss stabilising surgery.
In a trial after a first dislocation, a brace that limited the knee to 0 to 30 degrees for 4 weeks didn't reduce repeat dislocations compared with a soft neoprene sleeve (34% against 38% at 3 years), and it caused more thigh wasting, less knee movement and worse function at 6 months. The trial was small for this question.
NHS leaflets differ: one uses a brace for comfort for no longer than a week, because longer may raise the risk of further dislocations; another a splint for up to 2 weeks; another usually just a tubular elastic support. nidirect says a splint is for comfort and should come off for the exercises as soon as you can move your leg.
Tape, casts and splints: little evidenceMixed evidence
In one trial of 18 people, taping after a week in a back splint gave better knee scores than a cast at 6 and 12 weeks and at 5 years. Reviews find the evidence on casts, splints, braces and tape scarce and low quality, and no non-surgical method has been shown to beat another.
Whole-thigh and hip strength, not one special muscleEmerging evidence
In a trial of 50 people after a first dislocation, exercises aimed at the inner thigh muscle (vastus medialis obliquus, VMO) were no better than general thigh strengthening; the general group scored slightly better at a year, though not by a meaningful amount, and half dropped out. Reviews centre rehab on settling pain and swelling, regaining movement, and strengthening the thigh, hip and side-trunk muscles.
The UK PRePPeD trial programme starts with knee bending, thigh tightening, balance and squats to a chair, then builds strength at 1 to 3 sets of 8 to 12, at least three times a week, while retraining knee and trunk alignment in everyday moves to lower the risk of another dislocation. A pilot trial in 50 people found a full trial feasible; whether the programme works better than other approaches isn't known yet.
Back to sport: by checks, not datesEmerging evidence
Reviews set the checks as no pain or swelling, full movement, nearly equal strength and good control in fast, dynamic moves; with or without surgery, about two-thirds return to sport at the same level. NHS leaflets say at least 6 to 8 weeks, with full strength, full movement and brisk walking without pain or swelling first.
0 to 3 out of 10, and watch the swellingEmerging evidence
Keep pain between 0 and 3 out of 10 (as an NHS leaflet advises for knee ligament injuries; not tested after kneecap dislocation). If it goes higher, cut the repetitions or the load. If the injured knee measures more than 1 cm bigger round the middle than the other, measured with a soft tape, you've probably done too much; let it settle before carrying on.
An NHS kneecap leaflet says the exercises shouldn't cause excessive pain, and that early on you may not be able to bend the knee far.
One rule for the kneecap itself (this site's suggestion): if it feels as if it's about to slip, stop or make the movement smaller. The knee pain hub allows up to 5 out of 10 for long-standing knee pain; after a dislocation, keep to the lower ceiling until you're back in sport.
Start at the first stage. Each move opens a full guide with a 3D demo.
Stage 1
Settle and switch the thigh on (about weeks 0 to 2, as your team allows)
Start the exercises straight away. Use a splint or brace only as your team advises, taking it off for the exercises, and crutches if you're limping. Ice for 10 to 15 minutes at a time, at least 3 times a day, rest with the leg raised and supported, and don't twist the knee. Doses are NHS leaflets' unless marked.
Move on when: You walk without crutches or a limp, the knee straightens fully, the swelling is settling, and you can lift the straight leg without the knee bending.
Follow along: a timer, a cue and the next move, one step at a time.
Stage 2
Strength in the comfortable range (about weeks 2 to 6, as your team allows)
Strength 2 to 3 times a week, 3 sets of 8 to 12 with a rest day between, keeping the knee over the middle of the foot. No twisting on a planted foot yet. The sets and the cycling follow an NHS knee ligament leaflet; other doses are editorial unless named.
Move on when: Movement is full, sessions don't leave the knee more swollen (the 1 cm tape check), and you can do 3 sets of 12 sit-to-stands and step-ups with the knee over the foot.
Follow along: a timer, a cue and the next move, one step at a time.
Stage 3
Single-leg control, hips and trunk (about weeks 6 to 12, as your team allows)
Heavier and single-leg work, training the knee to stay over the foot, with the hip and side-trunk muscles. The split squat, single-leg deadlift and 60-second balance doses follow an NHS knee ligament leaflet; the rest are editorial.
Move on when: Thigh strength is close to the other side (a physiotherapist can test it), single-leg squats keep the knee over the foot, and the kneecap doesn't feel as if it will slip.
Follow along: a timer, a cue and the next move, one step at a time.
Stage 4
Landing, cutting and back to sport (at least 6 to 8 weeks, as your team allows)
Jumping, hopping and changes of direction once strength and control are back. Return when there's no pain or swelling, movement is full, strength is close to the other side and you feel confident in the knee. The knee control warm-up 2 to 3 times a week suits this stage. Doses are editorial.
Move on when: You can train fully with no pain, swelling or feeling that the kneecap will slip; then matches. Keep the strength work and warm-up going.
Follow along: a timer, a cue and the next move, one step at a time.
What to change for now
What to do now
If it has just happened, keep the knee still and supported with padding, such as rolled-up towels or cushions. Don't raise it, stand or walk on it, or try to put the kneecap back yourself. Go to A&E if the knee has changed shape, swelled very fast, you felt a pop or snap, or bone is showing; contact NHS 111 if the kneecap went back by itself.
Wear a splint or brace only as your team advises, and take it off for the exercises as soon as you can move your leg. Use crutches until you can walk without a limp. Don't drive until you can walk without crutches and do an emergency stop safely, out of any splint.
Keep the knee still and supported, and don't raise it, stand on it or try to put it back yourself. Go to A&E if the knee has changed shape, swells very quickly, you felt a pop or snap, or bone is showing; call 999 if you can't get there.
My kneecap popped out and went back in. Do I still need to be seen?
Yes: contact NHS 111. You'll usually need an X-ray to check that no piece of bone or cartilage has been knocked off.
How long does a dislocated kneecap take to heal?
The soft tissues usually take about 6 weeks, full recovery can take several months, and sport at least 6 to 8 weeks. In one study of 160 teenagers, nearly half took more than 6 months to get back to sport.
Will my kneecap dislocate again?
About 1 in 3 people dislocate again after a first dislocation. The risk is higher in younger people, while the growth plates are open, and with a shallow groove or a high-riding kneecap.
Do I need surgery?
Usually not after a first dislocation. A Cochrane review found surgery might lower the chance of another dislocation, but the evidence is very uncertain and knee function wasn't clearly better. Surgery is more likely if there's other damage or it keeps happening.
Should I wear a knee brace?
Only as your team advises, for comfort, and take it off for the exercises. In a trial, a movement-limiting brace didn't prevent repeat dislocations and caused more thigh wasting and stiffness than a soft sleeve.
What exercises help after a dislocated kneecap?
Start straight away with thigh tightening, straight-leg raises and knee bending, then sit-to-stands, step-ups, hip strength and balance. General thigh strengthening works as well as special inner-thigh exercises.
Does taping help?
In one small trial, taping gave better knee function than a cast, but the evidence on taping and bracing is limited. A physiotherapist may use it for comfort alongside exercise.
When can I go back to sport?
When you have no pain or swelling, full movement, strength close to the other leg and confidence in the knee. You need to run, change direction and jump without problems first.
Is it the same as runner's knee?
No. Runner's knee is pain around the kneecap without it coming out of place, and has its own guide. A twist with a pop and fast swelling can also be an ACL injury, so get it examined.
When can I drive?
When you can walk without crutches and do an emergency stop safely, out of any splint. Check with your team and your insurer if you're unsure.
Exercise education, not a diagnosis or treatment plan. It is written from the guidelines and studies listed above; review by a clinician is pending. If your pain follows an injury, is severe, is getting worse, or comes with any warning sign listed on this page, get it assessed. Health disclaimer.
