KNEECAP INJURIES

The kneecap bone (patella) sits in a groove on the thigh bone (femur). As the knee bends and straightens, the normally functioning patella slides smoothly up and down in this groove, known as the femoral groove (below right). The patella is held in place by the thigh (quadriceps) muscles, the tendon from the knee cap to the shin bone (patellar tendon) and ligaments on either side. Collectively, this group of structures in known as the patello-femoral joint (PFJ). 

Dysfunctions of the PFJ are extremely common in adolescents, in people who are very active and in people recovering from knee joint surgery. Usually, a vague pain is experienced around or behind the kneecap which is made worse with activities such as going up or down stairs, running and squatting.

What causes Patello-Femoral Pain?

PFJ pain is caused when the patella doesn't slide in the centre of the femoral groove. More often than not, the patella will slide to the outside of the groove. The bony surfaces can rub against each other and this causes irritation of pain-sensitive structures between the patella and femur.

There are many reasons that a patella may not sit properly in the femoral groove. Among the contributing factors are muscle imbalances and biomechanical changes. If there is weakness or poor control of the inside portion of the quadriceps muscle, the kneecap will slide outwards as the knee is bent. This weakness may be due to factors like muscle wasting after surgery, or more subtle changes like muscle fatigue due to excessive training. Likewise, if the outside quadriceps muscle is tight, it may drag the patella outwards as it contracts.

Poor biomechanics (movement patterns) at the hip joint or of the feet can also predispose a person to PFJ pain. Poor control of movements can lead to the knee 'rolling in' when the foot hit the ground while running and going up or down stairs. This can cause and outwards force on the kneecap, exacerbating pain.

Treatment

Because there are many factors which contribute to the onset of PFJ pain, treatment involves a combination of approaches.

Most patients will undergo a strengthening regime for the quadriceps muscles. The exercises given will be specific to the patient and gradually increased according to the functional requirements. Stretching of tight muscles, particularly calf and hamstrings, will usually also be included. 

Muscle control deficits are addressed through a variety of stretching and strengthening activities. These exercises have an emphasis on joint movement control more so than strength and are particularly important if the patient has biomechanical issues. Abnormalities in foot mechanics may need to be addressed with orthotics, available from your Symmetry Physiotherapy clinic