The patella occasionally can dislocate or pop out the knee joint to the outside. This is occurs more frequently in women than men and usually involves a distinct injury where the knee cap slides outside of the normal groove on the top of the knee. In most situations the patella will pop back into place on its own and only occasionally will the knee have to be extended to manipulate it back in place. The knee can be quite swollen after dislocations.
Treatment for this depends on how often this has happened. In first time dislocations, the knee is treated usually with bracing and physical therapy. Occasionally, an MRI may be ordered if there is concern that there was an associated injury to the cartilage on the undersurface of the patella. For those who have dislocated multiple times and the knee can not be trusted, surgery is often recommended to either repair the soft tissue restraints around the patella and or to correct the alignment of the joint.