The patella is the bone in the front of the knee, also known as the “knee cap.” With twisting injuries to the knee, the patella can pop out of place or dislocate. If it pops partially out of place and comes right back, it is called a subluxation, but if it comes completely out of its normal groove, it is termed a patellar dislocation. Once patients sustain a patellar dislocation, they are at a higher risk for recurrent patellar dislocations.
How it happens
Patellar dislocations occur most commonly in sports, but they can occur from any twisting injury that involves the knee. They can also occur with other types of trauma, such as a fall, and may be associated with other injuries to the knee. Some patellar dislocations are associated with injuries to cartilage and bone. In these cases, a small piece of bone and cartilage can break off from the trauma of the knee cap popping out of place. The knee usually swells up after these injuries.
How it feels
After the patella pops out of place, the knee is usually painful and swollen. Patients will usually have trouble walking, and even after it heals they may feel a sense of instability relating to the patella sliding out of place.
How it is fixed
Patients who have a first-time patellar instability episode may be treated without surgery. However, if they have a loose body (a fragment of bone or cartilage that has broken off and is floating the knee) surgery is generally recommended. Patients that have repeat episodes of dislocation or subluxation will usually elect to have surgery because the instability will affect their activity level and they will not be able to do their preferred sports and other activities. The surgery involves reconstruction of the medial patellofemoral ligament using a tendon graft. In some cases, tibial tubercle osteotomy may be performed as well to correct alignment problems.
Medial patella femoral ligament reconstruction is done as an outpatient procedure, meaning that the patient goes home the same day as the surgery. After surgery, a brace is used and patients can walk with crutches. Motion is started right away and most patients can walk normally within 4 to 6 weeks. Light jogging can be started at 3 to 4 months and full return to sports usually occurs between 4 to 6 months after surgery, but it can be much longer. The vast majority of patients experience excellent results following the procedure and eliminate the instability problem.