Runner's knee: symptoms, treatment and how long it takes to recover

Patellofemoral pain syndrome, shortened to PFPS, is a common knee condition in which pain arises at the front of the knee around the patellofemoral joint. This is the joint between the kneecap (patella) and the thigh bone (femur). Pain is most commonly felt around or behind the kneecap.

"Runner's knee" is the popular name, but it is a little misleading. NHS Lanarkshire says PFPS affects people who take part in sport and those who do not, men and women of all age groups. What links most cases is a change in how much load the knee is asked to carry, rather than a single dramatic injury.

It is not a sign of damage that will wear the joint out. NHS Lanarkshire describes it as a condition that usually responds well to exercise and lifestyle changes.

NHS Lanarkshire's physiotherapy service summarises the research this way: exercise reduces pain in the short, medium and long term, improves function in the medium and short term, and combining hip and knee exercises (such as squats) is recommended for all patients. Exercise is the core of treatment.

Three kinds of exercise are described: strengthening, stretching and endurance. Strengthening the hip and knee muscles is the priority, and the service says doing combined hip and knee exercises is the most effective. The aim is exercise that challenges the muscles but is relatively pain-free, done regularly (usually daily) for 12 weeks. You start with early-stage exercises and move on to the middle and late stages only when each level feels easy. If an exercise becomes painful, drop back to an easier level.

Stretching hamstrings, quadriceps and calf muscles can loosen tight muscles around the hip and knee. Endurance work such as walking, cycling or swimming is chosen to match your fitness and pain level and done several times a week.

Pain relief can help you stay active. The NHS suggests paracetamol or ibuprofen gel or tablets for knee pain. NHS Lanarkshire says paracetamol works better taken regularly in spread-out doses than as a one-off, that NSAIDs such as ibuprofen are not suitable for everyone, and that medication alone is unlikely to clear the pain completely. Speak to a GP or pharmacist if painkillers are not helping or cause side effects.

Pain is the main symptom. NHS Lanarkshire describes an ache at the front of the knee that can sharpen with certain activities, ranging from mild to severe, in one knee or both.

Some people hear or feel clicking or grinding when the knee bends or straightens. NHS Lanarkshire says this does not mean you are causing damage and that it is important to keep the knee moving. The NHS knee pain page agrees that painless clicking is normal.

• Pain at the front of the knee, around and behind the kneecap.

• Pain that gets worse during or after more activity than usual.

• Pain after sitting for a long time.

• Pain when squatting or going down stairs.

• Clicking or grinding when the knee bends or straightens, sometimes without pain.

Progress is gradual. NHS Lanarkshire says it can take 6 to 8 weeks of doing specific exercises to notice a difference in your knee pain, and a further couple of months before you feel better. It may take up to 12 weeks before you notice a significant improvement, with some gradual gains along the way. Change will not happen overnight, so consistency matters more than intensity.

Flare-ups are common and some people have recurrent ones. The same service says that in most cases a flare-up settles within 6 weeks. Rest a little more while it is sore, but keep active so the knee does not stiffen and the muscles do not weaken.

If symptoms have not improved after 6 to 12 weeks of following the advice, a referral to a physiotherapist may help, through a self-referral form where one is offered, or via a GP. The NHS adds that in many areas you can get help such as physiotherapy from NHS community musculoskeletal (MSK) services without a GP referral, and says to see a GP if knee pain has not improved within a few weeks.

PFPS usually occurs without an injury, though a fall onto the knee can very occasionally trigger it. NHS Lanarkshire says that if you have not injured the knee it may be difficult to find one specific cause, as it often has several.

The service uses the idea of a comfort zone: day to day your knee copes happily with a certain level of load. A sudden change, such as working extra shifts on your feet or a big rise in running distance, can take the knee outside that zone and make it sore without any physical injury.

• Starting a new activity.

• Increasing the intensity or frequency of an existing activity.

• Returning after a period of reduced activity that has weakened the muscles.

• Tightness or weakness in the muscles around the hip and knee.

• Unsupportive footwear such as high heels or very flat shoes.

• A job that involves frequent, prolonged kneeling.

• Being overweight.

Usually you can keep active, but adapt. NHS Lanarkshire recommends pacing yourself rather than stopping all movement, because stopping everything would make the muscles weaker and could worsen the pain. If running hurts, reduce how long you run or choose a flatter route. Another option is to swap to swimming or cycling and build leg strength that way, or to choose lower-impact exercise (one foot on the ground at a time) over high-impact work (both feet off the ground).

Newcastle Hospitals' advice for runners says pain while running is most commonly linked to tissue overload, which can lead to shin splints, hip and knee pain and Achilles tendinopathy. Common causes of overload include returning to running after time off, running more often with less recovery, increasing distance for a race, and changing surface or type of running.

Its suggested safeguard is progressive overload, sometimes called the 10% rule: when increasing running distance, build up by around 10% a time so the body can adapt. It also recommends cross-training with the cross-trainer, swimming or cycling to work different muscle groups, and points to free structured programmes such as Couch to 5K for beginners.

Knee pain has many causes, and the NHS cautions against self-diagnosis. The table sets out some look-alikes from the NHS knee pain page. If your pain does not fit the usual pattern, or does not improve, see a GP or a physiotherapist for a proper assessment.

The NHS says to get advice from 111 now if any of the following apply. 111 will tell you what to do and can direct you to the right place if you need to be seen. You can also go to an urgent treatment centre (sometimes called a walk-in centre or minor injuries unit).

• Your knee is very painful.

• You cannot move your knee or put any weight on it.

• Your knee is badly swollen or has changed shape.

• Your knee locks, gives way or painfully clicks (painless clicking is normal).

• You have a very high temperature, or feel hot, cold or shivery, and have redness or heat around the knee, which can be a sign of infection.

On the NHS, knee pain is usually managed first with self-care and exercise. If it does not improve, options include self-referral to community MSK physiotherapy where your area offers it, or a GP appointment, which can lead to medicine, physiotherapy or referral for a scan or specialist opinion if needed.

Some people choose to see a physiotherapist privately for a faster assessment or a supervised programme. The exercise principles are the same in either setting, so a programme built on progressive hip and knee strengthening is what to expect.