Pain around or behind the kneecap when performing activities such as squatting, ascending or descending stairs, and running is known as patellofemoral pain(PDFP). It has also recently been called "kneecap pain".

It is a very common condition and affects up to 25 per cent of the population. Usually, it is not caused by a specific injury but can occur in some cases due to "overload" from a new activity or a rapid increase in the amount of activity that you are already familiar with.

How is patellofemoral pain diagnosed?

Your physiotherapist will take you through a series of questions and a physical examination before confirming this diagnosis.

Usually, it is a clinical diagnosis, which means that no X-rays or scans are needed.

Pain is caused by mechanical factors (for example, how you move and how strong your muscles are) and usually structural changes in the joint, cartilage or ligaments are not associated with it.

What causes PFP?

Patellofemoral pain can be caused by a sudden increase in the amount of weight-bearing activity, such as walking or running.

Some of the other mechanical factors that can influence PFP are:

• muscle weakness around the abdominals, hips and thigh muscles
• poor movement control (usually noted during assessment and will be pointed out to you by your physiotherapist)
• inflexibility around the hip or ankle region
• increased foot mobility, flat feet or "rolling in".

How is it treated?

The good news is that the vast majority of research suggests that exercise therapy is the best treatment.

Your physiotherapist will provide you with more detail on this, but a combination of trunk (abdominal), hip (buttock) and thigh muscle strengthening is widely recommended.

Other treatments such as taping and insoles can reduce pain and help increase your ability to exercise, which is the most important part of your rehabilitation.

How long does it take to get better?

Although some reduction in pain levels can be expected four to six weeks after your rehabilitation has commenced, it will normally take 10 to 12 weeks of progressive strengthening of the aforementioned muscles for it to have a significant impact on pain and function.

Can I exercise with pain?

Yes, as long as the exercises only cause acceptable levels of pain (4/10 on your pain scale), you can continue to do them.

The same measure applies when performing activities other than the exercises recommended by your physiotherapist (for example, walking, running and cycling).

Another useful measure is how long the pain lasts after exercise or physical activity.

If it settles within 24 hours, it is okay to continue with those activities.

Staging exercises

During the initial stages, if your knee pain is very irritable, then you may be better off starting with strengthening exercises for your hip and trunk muscles (for the first four weeks or so). This may offload the sensitive structures around the knee and reduce your pain.

Thigh muscle strengthening can gradually be introduced after week four.

In order to get good improvements in pain, function and strength, the intensity (load or weights) of your exercises needs to increase gradually.

Exercising at the same intensity for many weeks will be ineffective. Your physiotherapist will guide you through this.

The good news is that as long as your exercise programme is challenging enough, you will only need to do them three times per week.