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Alternative names Return to top
Dislocation - knee cap; Patellar dislocation or instabilityDefinition Return to top
A dislocated knee cap is when the triangular bone covering the knee (patella) moves or slides out of place. The displacement usually occurs toward the outside of the leg. See dislocation.
Considerations Return to top
The doctor will conduct a physical examination, which could provide a visual confirmation of the dislocated knee cap. In addition, touching the knee cap during the examination would confirm that it moves abnormally.
A knee X-ray may be performed, confirming dislocation.
Causes Return to top
Dislocated knee caps most often occur in women with certain anatomic features of the knee, which predispose them to this condition.
It is usually a result of sudden direction changes while running. This puts the knee under stress. Dislocation may also occur as a direct result of injury. When it is dislocated, the knee cap may slip sideways and around to the outside of the knee.
The first episode or first several episodes are accompanied by pain and inability to walk. If the condition causing dislocation is left uncorrected, repeat dislocations tend to cause less pain and less immediate disability. However, they remain just as damaging to the patellar/femoral joint.
Symptoms Return to top
First Aid Return to top
Initial treatment consists of a knee immobilizer or cylinder cast, followed by gentle active range-of-motion (ROM) exercises. Physical therapy should be involved to help regain joint and leg strength, especially the quadriceps muscles. Taping techniques have been explored with variable results.
Surgery may be necessary to "redirect" the patella; this may be either by arthroscopic or "open" surgical reconstruction.
Call immediately for emergency medical assistance if Return to top
Call your health care provider if you injure your knee and symptoms of dislocation occur.
Call your health care provider if you are being treated for a disloctaed knee and you notice increased instability in your knee, if pain or swelling return after they initially subsided, or if your injury does not appear to be resolving with time.
Also call if you re-injure your knee.
Prevention Return to top
Use proper technique when exercising or playing sports. Maintain strength and flexibility of the knee. Some cases of knee dislocation may not be preventable, expecially if anatomic factors predispose you to dislocation.
Update Date: 8/3/2004 Updated by: Kevin B. Freedman, M.D., Section of Sports Medicine, Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |