Patellofemoral pain syndrome (knee pain in young adults)

What is patellofemoral pain syndrome?

Patellofemoral pain syndrome is often caused by imbalances in the muscles surrounding the knee, which affect the kneecap (patella) and cartilage within the joint. As many as 1 in 3 young adults experience this type of knee pain at some time or other.


The main symptoms of patellofemoral pain syndrome are:

  • Pain

You may feel pain in the front of your knee and around and behind your kneecap. It can sometimes be quite severe and everyday movements like walking up and down stairs can make it worse. You may also feel a dull ache, for example after you’ve been sitting for a long time. The pain often makes it difficult to kneel or squat. It’s often aggravated by running, so it frequently occurs during or after you’ve played sport.

  • Crepitus

Changes in the surface of your cartilage can cause a scratching or grating sensation from the kneecap, which you may be able to hear when you bend or straighten your knee. Crepitus doesn’t often cause pain.

The effect of these symptoms on your everyday life can vary from time to time.


We don’t yet fully understand all the causes of patellofemoral pain syndrome, but it’s most likely a combination of factors. Some factors that could lead to it are:

  • weakness or imbalance in your thigh or buttock muscles
  • tight hamstrings (the muscles at the backs of your thighs)
  • short ligaments around your kneecap
  • problems with weight bearing and alignment through your feet

An imbalance in the muscles surrounding your knee can put too much pressure on your kneecap and the cartilage in your joint. To understand why this happens, it helps to know a little about how your knee joint works.

A diagram of the anatomy of a joint which doesn’t have arthritis, showing how bones and muscles are connected.

The kneecap (patella) lies in a groove at the front of the lower end of the thigh bone (femur). It’s shaped to move up and down in the centre of its groove when you bend or straighten your knee. If the muscles or ligaments surrounding your knee cause your kneecap to move away from the centre of its groove, this can put too much pressure on the cartilage which lines the side of the groove and on a small area on the back of your kneecap. This pressure can lead to changes in a small area of cartilage where your kneecap meets your femur, which can lead to knee pain.

How will patellofemoral pain syndrome affect me?

The outlook is very good. Your knee will probably get better either by itself or with simple painkillers and exercises. There’s no link between this kind of knee pain and generalised arthritis later on in life.


Patellofemoral pain syndrome is fairly easy to diagnose. Your own doctor (GP) will make a diagnosis based on:

  • your symptoms
  • a physical examination of your knee

To check for any changes behind your kneecap that could be causing your symptoms, your doctor may ask you to tighten your thigh muscles (quadriceps) while they hold your kneecap down, as this will reproduce the pain. Occasionally, increased fluid in the joint can cause swelling, so your doctor will also check for this.

Blood tests don’t help in diagnosing patellofemoral pain syndrome but may be useful for ruling out more serious problems. X-rays aren’t usually helpful as cartilage doesn’t show up on them. Your doctor may suggest a magnetic resonance imaging (MRI) scan, for example if you’ve had a blow to your knee.


Patellofemoral pain syndrome sometimes gets better on its own without any treatment, though you may have symptoms for several years. However, painkillers and physiotherapy can help to reduce your pain.


Simple painkillers (analgesics) such as paracetamol can help to ease pain. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, may not offer any additional benefit over paracetamol, and NSAIDs are more likely to have side-effects.


It’s important to keep your thigh muscles (quadriceps) strong and balanced to avoid putting pressure on your knee joint. Your doctor may give you exercises to do or suggest that you see a physiotherapist who will be able to suggest other exercises if necessary. They’ll assess your knee and decide what’s causing the pain and which exercises will best fit your particular problem. They’ll also make sure that you’re doing the exercises properly and safely.

It may take at least 12 weeks of doing exercises several times a day for a total of 30 minutes a day before any muscle imbalance or weakness is corrected, and it could be some time after that until the pain completely settles down.

Read more about physiotherapy.

Managing symptoms


It’s important to exercise your thigh muscles (quadriceps) to stop them from becoming weak. Swimming is an excellent form of exercise, and front and back crawl will put less strain on your knees. You should avoid sports that put a lot of pressure on your knees, like football, rugby or cross-country running, if they make the pain worse, although it should be possible to start these again once symptoms have eased.

Wall squats will be helpful if you do them regularly.

  • Stand with your back against a wall, feet together or apart at a 30° angle.
  • Slide down the wall by bending your knees, until you can no longer see your toes.
  • Hold this position and clench your buttocks for 5–10 seconds.
  • Relax and repeat the whole exercise as many times as possible.

Your physiotherapist may recommend additional exercises.


You don’t need to stay away from school, though you may have to make arrangements to make sure you don’t overwork your knee. If the walk to school, certain sports or climbing stairs make your pain worse, talk to a teacher about it.