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Patellofemoral Pain
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Patellofemoral Pain

The kneecap (patella) is the flat, oval bone at the front of your knee. It is held in place by a broad tendon and one of the largest muscles in the body, the thigh muscle (quadriceps).

The patella, its tendon and the quadriceps are responsible for the ability to stand, walk, jump and kneel. During these movements, a normal functioning kneecap slides up and down a groove on the end of the femur as the knee bends.

What is Patellofemoral Pain?

Patellofemoral (PF) pain, is pain in, behind or around your kneecap (patella; see Figure 1). You may get pain when the kneecap moves differently from usual. The cartilage covering the bones in the area behind the kneecap – known as the PF compartment – may also be damaged.

PF pain is the most common problem in knees. As many as one-third of all patients who visit an orthopaedic specialist for knee pain will have PF pain.

When a patient with PF pain is asked to point at where it hurts, the patient most often grabs the whole knee and says that the pain is in the front of the knee, somewhere around the kneecap. It is often difficult to localise a more specific point than that.

Most patients with PF pain say that the pain gets worse when going downhill or down the stairs. Some patients also say that pain also increases when going uphill or when sitting with the knee bent for a long time.

What causes patellofemoral pain?

There could be a variety of causes for PF pain. It is therefore necessary to do a detailed search to determine the specific causes of pain. The pain may be caused by too high pressure on local areas of the PF compartment. It is possible to have healthy cartilage in the PF compartment but still have major pain due to high pressure and overloading of structures in the knee.

Common causes of PF compartment pain are:

  • Injury (e.g. dislocation, fracture or tear of a structure)
  • A poorly aligned kneecap (a lateralization of the kneecap) – which means that pressure on the outer side of the kneecap is too high. A kneecap can be poorly aligned due to soft tissue problems (e.g. a lack of muscular strength) or due to anatomical abnormalities (e.g. bones in the leg have an unusual shape or direction)
  • Wrong gait (walking or running in a wrong way – for instance, it is common to put too much weight on your heel)

Excess weight can also cause issues that will lead to PF pain

How is PF pain diagnosed?

Confirming a PF problem is not straightforward. The specialist will first do a thorough clinical examination of yourknee. He or she will push the patella in different directions, put pressure on different parts, lift it up from each side and flex and extend your leg in order to locate the area that cases the pain.

After the clinical examination, the doctor may also use diagnostic imaging tests such as X-ray, computed tomography (CT) or magnetic resonance imaging (MRI) in order to find the underlying reasons for the pain.

Anatomical abnormalities can initially be diagnosed by looking at an X-ray. If abnormalities are found, then the next step is normally to have a CT or MRI scan to diagnose underlying anatomic abnormalities, which may be the cause of the problem.

Conservative treatment

Once the patellofemoral compartment is confirmed as the main source of pain, the goal is to plan a comprehensive treatment programme to minimise the potential of multiple surgeries.

The vast majority of PF pain (over 95% of cases) responds to physical therapy programmes of exercise and stretching. However, the most common reason patients do not respond well to this non-operative treatment is a failure to follow the most current therapy principles especially designed to help PF pain.

When choosing a physical therapist, patients should look for those who use techniques that focus on hip and pelvic muscular strength, rotational control and a technique known as ‘core strengthening’. The therapist should also include more traditional quadriceps (thigh muscle) strengthening.

The goal of the physical therapy is to normalise the anatomical behaviour of the knee joint. Such a programme can take up to nine months, but there should be signs of improvement after about six weeks.

If there is no improvement after six weeks, then the underlying cause might be an anatomical problem that would need to be further examined by the orthopaedic expert. If the rehabilitation of the PF joint does not lead to improved comfort and function, surgical options may be discussed.

Surgical treatment

Surgery should only be considered after failure of a comprehensive rehabilitation programme. The type of surgical treatment depends on the type of disease affecting the patellofemoral joint.

In cases of traumatic injury and cartilage damage to the PF joint, a number of different cartilage repair options and soft-tissue repair methods can be considered. The outcome of cartilage repair on the patella (kneecap) is highly variable. The main reason for this is that the patella has very little blood supply, which results in a lower potential for successful cartilage regeneration compared to other joints.

When anatomical abnormalities that result in instability are believed to be the underlying cause of PF pain, some other types of surgical procedures might be considered. Medial patella-femoral ligament (MPFL) reconstruction is the most common surgical procedure in reducing PF instability caused by anatomical abnormalities.

Other surgical procedures used to correct serious and recurring dislocation of the kneecap (and to reduce pain) include tibia tubercle realignment (also known as a tibia tubercle transfer) and bone reshaping (trochleoplasty).

The patellofemoral joint is very complex and there are several potential causes of pain (see ‘What causes patellofemoral pain?’ above). Major surgery might reduce the pain, but patients should be aware that surgery might also increase the risk of increasing the amount of pain and for developing osteoarthritis in the longer term.

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