Patellofemoral pain is the medical term used when pain occurs at the front of the knee, around the patella (kneecap), without signs of any damage or other problems in the knee joint.
It is also called patellofemoral pain syndrome or patellofemoral syndrome.
What is the patella?
The patella is the kneecap bone. It lies within the quadriceps tendon. This large tendon from the powerful thigh muscles (quadriceps) wraps round the patella and inserts into the top of the lower leg bone (tibia). The quadriceps muscles straighten the leg. The patella acts like a fulcrum to increase the force of the quadriceps muscle.
The back of the patella is covered with smooth cartilage. This helps the patella to glide over the lower part of the thigh bone (femur) when you straighten your leg.
What causes patellofemoral pain?
It is probably due to a combination of different factors which put extra strain on the knee joint and on the surrounding muscles and ligaments.
Situations where this can occur include:
- Overuse of the knee, such as in certain sports - particularly at times of increased training.
- Some people may have a slight problem in the alignment of the knee. This may cause the patella to rub on rather than glide over the lower femur. It may be due to the way the knee has developed. Or, it may be due to an imbalance in the muscles around the knee - for example, the large quadriceps muscle above the knee. If one side of the quadriceps muscles pulls harder than the other side, then the patella may not glide 'true' and may rub on one side.
- A combination of an alignment problem (as above) and overuse with sports, may be the commonest reason for getting patellofemoral pain.
- Foot problems can play a part. For example, where the feet do not have strong arches ('flat feet'). This makes the foot roll inwards ('pronate'), which means the knee has to compensate for the inward movement. Also, shoes where the soles are hard rather than springy, put more strain on the knee.
- Injury to the knee - including repeated small injuries or stresses due to sports, or due to slack ligaments ('hypermobile' joints).
- Reduced muscle strength in the leg can contribute, as the leg muscles will be less able to absorb stresses on the knee.
Who gets patellofemoral pain?
Almost anyone - it can occur in children from about age five onwards, and in adults. It is a common cause of knee pain.
What are the symptoms of patellofemoral pain?
- Pain around the knee. The pain is felt at the front of the knee, around or behind the knee cap. Often, the exact site of the pain cannot be pinpointed; instead the pain is felt vaguely at the front of the knee.
- The pain comes and goes. It is typically worse when going up or down stairs or with certain sports. Also, it may be brought on by sitting still for long periods. For example, after going to the cinema or a long drive.
- There may be a grating or grinding feeling or noise when the knee moves. This is called 'crepitus'.
- Sometimes there is fullness or swelling around the patella.