Patellofemoral pain syndrome (runner’s knee)

Pain at the front of the knee usually occurs just behind or next to the kneecap. Doctors then call it patellofemoral pain or patellofemoral pain syndrome (PFPS). “Patellofemoral” means that it affects the area between the kneecap (patella) and the thigh bone (femur).

The pain is often mild at first and then gets worse over time. It tends to be a dull, aching pain and is particularly noticeable when you put strain on the knee – especially when going up or down stairs or bending the knee a lot. The knee may also hurt and feel stiff after sitting for a long time.

A lot of people who have knee pain can feel or hear crackling, crunching or creaking when they move the affected knee. But this isn’t a reason for concern: There’s no link between knee sounds and pain or the function of the knee. Many people have “noisy knees” without any pain or other knee problems. One reason why joints sometimes make sounds is because small bubbles of gas form in them and you can hear the bubbles bursting.

People whose knees make sounds can – and should – still move. The knee joint can only stay healthy if it is moved enough. If no pressure is applied to it, the cartilage in the joint isn’t supplied with enough nutrients. The bones need to have strain put on them too, to stop them from becoming weaker.

Overuse of the knee can lead to small injuries around the kneecap – for instance, in the bands of tissue that hold it in place, in the bones and in the small nerves. It’s not clear why some people develop knee problems and others don’t. One factor that plays a role is how the kneecap moves along the trochlear groove in the joint. But specialists are also looking into other possible influences, including:

• Weak thigh and hip muscles
• Anatomical factors such as having one leg that is longer than the other
• Foot deformities
• Unusually short muscles
• Being knock-kneed or bow-legged

Although having a larger Q angle (the angle at which the upper leg bone meets the lower leg bone) is often thought to lead to knee pain, research so far hasn’t found a link between the Q angle and patellofemoral pain.

It’s still not clear how much of an influence the other factors have because past studies have produced conflicting results. So far, research has only suggested that having weak thigh muscles can increase the risk of knee pain.

In many cases knee pain is likely to be the result of a combination of various factors.

The main risk factor for pain around the kneecap is overuse. Activities that put a lot of strain on the front of the knee include jogging, mountaineering, going up and down stairs, and doing squats. Cycling sports can also lead to knee pain – especially if you cycle on hills, mountains or use high gears.

Overuse is more likely to occur if the activity is done for too long or too often, and if the intensity is too great or increased too quickly. Research has shown that pain at the front of the knee often develops in beginners, competitive runners and long-distance runners.

In some people the front knee pain is work-related – for instance, because they spend too much time in a squatting position or doing heavy lifting.

Pain at the front of the knee is one of the most common knee problems. It mainly affects teenagers and physically active people.

The pain can develop differently over time. About half of those affected only have pain for a few weeks or manage to get it under control within a few months. In the other half, the pain lasts for several years or keeps coming back.

Patellofemoral pain (runner's knee) is diagnosed based on the symptoms. In other words, if

• the knee hurts just behind or next to the kneecap,
• the pain occurs when you put stress on your knee, for instance when climbing stairs, jogging or sitting in a squatting position, and
• no other cause can be found.

The doctor first asks about the symptoms and feels the knee. Then she or he asks you to squat down. A different test involves slowly stepping off a step with the healthy leg. If that makes the pain worse, it could be patellofemoral pain. Some medical professionals also use special questionnaires to get a more accurate description of the symptoms.

If necessary, further knee tests are done to rule out other causes. These include things like a torn meniscus, osteoarthritis of the knee, and tendon-related problems. But osteoarthritis is very rare in people under the age of 40. Before the end of puberty, certain growth-related problems can cause knee pain too. These can also be ruled out by examining the knee.

Imaging techniques like x-rays, ultrasound scans or MRIs do not help to diagnose runner's knee. But it can make sense to use them if something else is thought to be causing the pain – such as a tendon overuse injury, osteoarthritis of the knee, or a bone fracture.

Good-quality studies have shown that acute pain can be relieved by resting the knee and – in the long term – regularly doing strengthening exercises.

• Resting the knee: People who do a lot of sports are advised to do less or stop for a while, to allow the knee to recover.
• Strengthening the thigh and hip muscles: Strengthening these groups of muscles takes some of the load off the knee joint. Regularly doing exercises can relieve the pain and improve the joint function.

Acute pain can also be treated with pain-relieving and inflammation-reducing gels or creams containing the drugs ibuprofen or diclofenac. They are applied to the knee 2 to 4 times a day. Gels and creams have fewer side effects than tablets with the same drug in them.

It is not a good idea to take painkillers just so you can do endurance sports again without pain. There are two main reasons for this: On the one hand, you need to rest the knee and, on the other, the medication reduces your kidney function. This can be more of a problem if you get hot, don’t drink enough, and overexert yourself because the kidney already has to work harder.

If your feet roll too far inward when you walk (overpronation), shoe inserts can be used too. Inserts probably help in some people, at least in the short term. But there aren't many good-quality studies on the effectiveness of shoe inserts.

It can be very frustrating if you’re no longer able to do activities that are important to you – or not as much as you used to, and only accompanied by pain. People who have joint pain often have to accept the fact that even the best doctors can’t always find out what is causing the pain. The treatment can take a long time and you have to be actively involved yourself.

The best thing you can do is stay positive and focus on the treatments that have been proven to work. If you have to take a forced break from your favorite sport, you could perhaps try out a different, pain-free activity for a while – such as low-intensity cycling, aqua jogging or swimming.

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.