The patella (kneecap) is connected to the tibia (shin bone) by the patellar tendon. The kneecap connects the muscles in the front of the thigh to the tibia. As the leg bends or straightens, the kneecap is pulled up or down. The thighbone (femur) has a V-shaped notch (femoral groove) at one end to allow the kneecap to move. Normally, the patella fits perfectly in the groove. But if the groove is uneven or too shallow, the patella could slide off, resulting in a partial or complete dislocation. The patella can dislocate outside of its normal position. A dislocated kneecap is not the same as a dislocation of the knee joint.
A patellar dislocation is usually a result of a sudden blow or twisting action of the knee. In most cases the patella will relocate to the patellofemoral groove when you straighten your knee, however this is usually quite painful.
Symptoms of a Dislocated kneecap
- Immediate pain
- Swelling in the knee joint
- Knee buckles under weight
- Cracking sounds during movement
- Obvious displacement of the kneecap
Patellofemoral Pain Syndrome
Patellofemoral pain syndrome describes knee pain in the front of the knee and around the patella (kneecap). It is common in athletes, particularly distance runners; however, it commonly occurs in non-athletes as well. Patellofemoral syndrome occurs when nerves sense pain in the soft tissues and bones around the kneecap. These soft tissues include the tendons, the fat pad (tissue beneath the patella) and the synovial tissue that lines the knee joint. In some cases a condition called chondromalacia patella is present. Chondromalacia patella is the softening and breakdown of the articular cartilage on the underside of the kneecap which can lead to inflammation of the synovium and pain in the underlying bone.
Patellofemoral pain syndrome is caused by physical activities that put repeated stress on the knee. These overuse activities include: running, squatting or climbing stairs. It can also be caused by a change in frequency of activity, improper use of equipment or a change in footwear. Patellar malalignment can also cause patellofemoral syndrome. This occurs when the kneecap is pushed out to one side of the groove when the knee is bent. This causes increased pressure in the back of the kneecap and irritates the soft tissues. However, it is important to understand that patellar malalignment and patellofemoral pain syndrome are not the same.
Patellofemoral syndrome symptoms
- Pain with prolonged sitting with knees bent
- Pain during activities that require repeatedly bending the knee
- Pain after change in activity level or intensity
- Popping or crackling sounds in the knee
Treatment for patellar dislocation and patellofemoral pain syndrome
In most cases symptoms will improve with home treatment. Including:
- Rest, Activity modification
- Non-steroidal anti-inflammatory drugs
- Physical therapy
Surgical treatment for is usually not performed and only necessary if your physician cannot determine the cause of your pain.