Dislocated kneecap: When is surgery recommended?

Experts often disagree on the issue of whether surgery should be done. Conservative treatment is typically used if it's the first time you have dislocated your kneecap. If it happens a second time or if it keeps happening, surgery is usually considered. Other factors that also play a role include:

• Which conservative treatments have already been tried
• Whether cartilage or bone have been damaged
• Whether you have misalignments or other risk factors
• Age and sports-related goals

It is a good idea to discuss the advantages and disadvantages of surgery with your orthopedist and then consider them on your own.

There are many different kinds of surgery to treat an unstable kneecap. The basic types are:

• Surgery on the joint capsule and the ligaments: This involves tightening or replacing parts of the capsule and ligaments that stabilize the kneecap on the inner side of the knee, particularly including the medial patellofemoral ligament (MPFL, see illustration). This ligament is usually torn the first time the kneecap is dislocated. Then it can be replaced by part of a tendon taken from the back part of the thigh muscles. This procedure is supposed to ensure that the kneecap doesn’t slip out of place so easily outwards (in the lateral direction).
• Surgery on the bones to correct anatomical misalignments: These procedures can deepen the trochlear groove that the kneecap fits into. It is also possible to move the patellar tendon on the shinbone to the side. The aim of doing this is to keep the kneecap in the middle of the groove when force is put on it. Sometimes the axis (alignment) of the leg is also corrected by straightening the thigh and lower leg and stabilizing them with a plate.

The techniques that are considered depend on the anatomical form of the knee and leg.

Researchers from the Cochrane Collaboration analyzed ten studies comparing surgery with conservative treatments. Over 500 teenagers and young adults participated in these studies.

Each of them had either conservative treatment or surgery. The surgery in these studies involved stitching and tightening the torn MPFL or replacing it with a tendon. There are currently no comparative studies on any of the other types of surgery.

Because the quality of the studies was too low, it’s not clear whether the surgery led to a greater improvement in symptoms and knee function than conservative treatment did.

Only one study provided information on the frequency of complications. A few of the people in this study had complications after surgery, such as an infection or a poorly healing wound.