A bipartite patella forms when a portion of the patella does not completely heal along the bony edges of the patella. Most commonly, this is in the upper and outer (superolateral) portion of the patella. Bipartite patella actually is quite common, usually asymptomatic, and is found in 2% of the population on x-rays. In the vast majority of people, a bipartite patella does not cause symptoms. Most often, it is found on an x-ray because a patient is experiencing symptoms that are being caused from another underlying condition.
In a small percentage of people, the bipartite patella can cause symptoms. Most commonly, this is found after an injury. In most cases, the usual fibrous connection between the two portions of the patella is disrupted and it does not heal back normally. Dr. LaPrade sees this in athletes who play ice hockey, and in athletes who may sustain contact to their knees (such as soccer and football players). The usual treatment for symptomatic bipartite patella is to try to avoid activities which cause irritation and allowing it time to quiet down. This could include avoiding contact, avoiding deep squats, lunges, and other activities which significantly stress the patellofemoral joint. In patients for whom this does not work, and who may have some other associated knee pain for which it is difficult to determine if the exact location of pain is coming from the bipartite patella, an injection into the fibrous union between the normal patella and the bipartite patella may help to differentiate if this is the source of pain. In most athletes, one can percuss on the bipartite patella area and it can duplicate their symptoms.
In patients who have limitations in function and who have undergone an appropriate period of time without any improvement of their symptoms, an arthroscopic excision of the bipartite patella has been found to be very effective. Usually, this requires 3-4 small incisions around the knee to take off this portion of the patella, shell it out arthroscopically with a bur, and to try to save the normal ligament structure on the lateral aspect of the patellofemoral joint. While one can excise them more quickly through an open incision, the open incision commonly can create a gap between the patella and the lateral retinaculum, which requires limitations of activities for a longer period of time. With an arthroscopic procedure, one can start early range of motion, weightbearing, and a slow progression of activities to increase their function.
Dr. LaPrade has found that arthroscopic excision of a bipartite patella to be very effective at relieving pain and improving function. When the athlete follows the rehabilitation precisely postoperatively, the results can be excellent after surgery. It takes most tissues of the body about 6 weeks to heal, so activities should be limited for a minimum of 6 weeks to make sure that one does not stress the area where the bipartite patella was shelled out and give it the best chance to heal in. If one follows this protocol, there is an excellent chance of a full return to function after an arthroscopic excision of a bipartite patella.
