The initial dislocation of a patella (kneecap) is usually a dramatic acute event that occurs during a knee twisting event. The patella will jump laterally (to the outside of the knee) and either stay there or pop back into place. The knee will swell a great deal immediately and the patient may or may not be able to bear weight on that leg.

How is a patellar dislocation diagnosed?
The diagnosis is based on the history given by the patient and by the physical examination.

Will x-rays be taken?
If this is the first time that the patella has dislocated, then x-rays will usually be taken. Sometimes, a MRI will also be ordered to look for any other problems in the knee or if a piece of bone has broken loose with the patellar dislocation.

What is the treatment for an initial patellar dislocation?
This is a controversial area of sports medicine. Depending on the age, physical examination, x-rays, and the athletic level of the patient, a treatment protocol will be initiated. Fortunately for adolescents, the treatment does not usually involve surgery. They will be maintained in a knee immobilizer or a cylinder cast. At a certain point in their rehabilitation, they will be sent to physical therapy to work on a stretching and strengthening program. Some patients will need to have surgery. This is sometimes performed arthroscopically (through a small camera), but also may require a regular surgical incision.

Does the patella ever dislocate again in these patients?
Yes, the incidence of having another dislocation is dependent on the age at which the first dislocation occurred. Younger children are more likely to have a recurrence. Some patients will have one or two more dislocations and others will begin having dislocations all of the time (or chronically). A patient that has had more than 6 dislocations may be a candidate for a surgical procedure to help keep the patella in place.

What are the long-term problems associated with a patellar dislocation?
A great deal of force is required to pop the patella out of joint. This force is transferred into the joint where the articular cartilage (pearly white stuff on the ends of all bones) may be damaged. This may lead to arthritis and other persistent problems. Having multiple episodes of dislocations increases the damage to the articular cartilage and puts the patient at increased risk for arthritis in the future.