Patellar instability and dislocations can plague both children and adults alike. The patella (kneecap) connects the muscles of the thigh to the tibia (shin bone). The patella should sits within a groove (trochlea) at the end of the thigh bone (femur). As the knee bends and straightens with sitting and standing, the patella should glide smoothly up and down within the groove. Unfortunately, sometimes the patella can slide partially out of the groove (subluxate) or slide completely out (dislocate) of the groove.  When either of these occurs, pain, swelling and loss of function ensues.

There are many causes for why and how the patella can become unstable or dislocate. Individuals can have a shallow groove that can make them more prone. Additionally, some patients have looser ligaments which can lead to patellar instability. Commonly, the patella dislocates due to a direct blow or fall on the knee.

Symptoms can vary from patient to patient with patellar instability and partial vs full dislocations. patients often report feeling something in their knee shift out of place as well as feelings of catching and popping within the kne. The knee then swells and is painful. Patellar instability can have more subtle symptoms such as pain while sitting, an increase in pain to the front of the knee with activity, swelling, and clicking/cracking in the joint with movement.

To make the proper diagnosis, we take a thorough history from the patient and do a physical exam of the knee. X-ray imaging is also very helpful to assess the bony structures and alignment of the knee joint, paying particular attention to the shape of the groove and where the patella sits in relationship to the groove. MRI scans are sometimes ordered as well. These can help determine a better calculation of the trajectory of the patella in the groove as well as determine if there are any loose cartilage or bony fragments that could have been dislodged during a dislocation.

For patients who have suffered a first time dislocation, Dr. Cunningham recommends non-surgical treatment consisting of physical therapy with gentle range of motion exercises as well as strengthening of knee and hip musculature. In the Vail Valley where we have a lot of skiers, bikers and runners, athletes tend to be quite strong in their quads and hip flexors but relatively weaker in their hamstrings and glute muscles. Physical therapy and personalized strengthening programs are helpful in addressing this issue. Bracing is another good option for treating a patellar dislocation. We fit patients with a special brace that helps hold the patella centered in the groove.

Unfortunately, if a patient has had several patellar subluxations and or dislocations, then they are more likely to continue to have these instability episodes. As a result, patients find that there are unable to resume all the activities that they enjoy. In these cases of recurrent instability of the patella, surgery is usually required to stabilize the knee cap and allow patients to resume all of their sports. Surgery consists of a medial patellofemoral ligament (MPFL) reconstruction. The MPFL attaches from the femur to the inner aspect of the patella, and its main purpose is to stabilize the patella within the groove. When the patella dislocates, there is full or partial thickness tearing of the MPFL. In MPFL reconstruction surgery, Dr. Cunningham uses a piece of donor tendon to tighten and reinforce the stretched out MPFL, thus stabilizing the patella and preventing further dislocations. This is an outpatient surgery. A brace is required for 4-6 weeks after surgery. Physical therapy is started immediately after surgery. It can take 4 months to fully recover and have a patient resume full activities.

This article also appeared in The Vail Daily News.

Gretchen Meador, is a Physician Assistant with Dr. Rick Cunningham of Vail-Summit Orthopedics.