Description of Bipartite Patella
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 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.
Symptoms of Bipartite Patella:
- Localized pain over the superolateral patella
- Pain with deep squats or high level of ice skating or skiing
- Percussion of the patella over the bipartite portion almost always reproduces a patient’s symptoms
Most commonly, a bipartite patella is found after an injury. In most cases, the usual fibrous connection between the two portions of the bipartite 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).
Are you experiencing bipartite patella symptoms?
There are two ways to initiate a consultation with Dr. LaPrade:
You can provide current X-rays and/or MRIs for a clinical case review with Dr. LaPrade.
You can schedule an office consultation with Dr. LaPrade.
(Please keep reading below for more information on this condition.)
Treatment for Bipartite Patella
The usual treatment for symptomatic bipartite patella is to try to avoid activities that cause irritation and allowing it time to quiet down. This could include avoiding contact, avoiding deep squats, lunges, and other activities that 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.
Post-Op
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.
Bipartite Patella Injury FAQ
Bipartite patella is usually discovered as an incidental finding on an x-ray. It is present in about 2% of the population, which means that about 1 in 50 people do have a bipartite patella. Thus, while it is a fairly common finding, it is not very common that it does cause pain.
1. What to do for a bipartite patella?
Most patients who have a bipartite patella have it as an incidental finding, so usually no treatment is necessary. For those patients who do have symptoms, a program of rehabilitation and activity modification may allow the symptomatic bipartite patella to calm down.
2. How to read a bipartite patella MRI?
Most bipartite patellas will be asymptomatic. Thus, on an MRI scan, there should not be any increased signal between the bipartite patella and the main bony portion of the patella. For those patients who are symptomatic, the fibrous union between the bipartite patella and the main portion of the patella (kneecap) will have increased signal. In addition, often the bipartite fragment will tilt down towards the trochlea, rather than having a normal, smooth surface. These are the patients who usually have the most symptoms with a symptomatic bipartite patella.
3. When to have bipartite patella surgery?
Most cases of bipartite patella do not cause any significant problems. If one does have an acute onset after a blow to the knee, a trial of rehabilitation and activity modification may prove useful to allow it to quiet down. In those patients who have a very symptomatic bipartite patella, which does cause them to limit their activities, an MRI scan can be useful to determine if there is increased signal between the bipartite patella fragment and the main portion of the patella. In addition, if the bipartite patella is tilted towards the trochlea, these patients often will need bipartite patella surgery.
Usually the bipartite patella itself is relatively small and not an essential portion of the kneecap. Thus, a surgical excision would be indicated in those patients who have a lot of symptoms and have a portion of the patella that is relatively small and not contributing significantly to the patella function. In these cases, an arthroscopic excision may be indicated. We prefer an arthroscopic excision over an open excision because patients can resume activities much sooner, and there is no disruption of the lateral retinacular attachment to the patella. Recovery from an open excision of a bipartite patella can be longer, and if the lateral retinaculum fails, the patients may develop symptomatic medial patellar instability symptoms.
4. What is a bipartite patella?
A bipartite patella forms when a bony growth center, called an ossification, that normally heals together in the kneecap does not completely heal. Most commonly, this is in the upper and outer portion of the kneecap, the superolateral portion.
5. How common is bipartite patella?
A bipartite patella is found as an incidental finding on about 2% of knee x-rays, which would mean that it is present in about 1 in 50 patients.
6. How does one treat bipartite patella?
The treatment of bipartite patella depends upon its presentation. In most circumstances, it would be recommended to try physical therapy and activity modification. In those cases where there is a new injury which leads to an irritation in the bipartite patella, this would be the usual course of treatment. In those patients who have tried extensive activity modification or therapy and still have significant symptoms in her bipartite patella, an evaluation as to whether continued observation or an arthroscopic excision should be performed should be evaluated.
7. How does one differentiate a bipartite patella from a patella fracture?
This is a good question because it is not uncommon for us to see patients who were felt to have a patella fracture when in fact it is a bipartite patella that has been irritated from an injury. An important thing to recognize about a bipartite patella is that most of these are located in the superolateral aspect of the patella. Most patella fractures will occur mid-body and are a transverse pattern that do not have any other obvious displacements. Certainly if one had a bad patella fracture, there would be no doubt about its diagnosis, so in these circumstances you then would be looking at a nondisplaced patella fracture versus a bipartite patella. Looking at the edges of the lesion should help to differentiate this also. A bipartite patella has usually been present for a long time, so the bony edges will be wider or sclerotic. However, a fracture would have well-defined and sharp edges that are not sclerotic in most circumstances.
8. What happens to athletes with bipartite patella?
Most athletes who present with a bipartite patella often have a blow to the kneecap that causes irritation of a previously undiagnosed bipartite patella. In most of these circumstances, activity modification and time will allow this to become less irritated. Those athletes who continue to have symptoms may have had the bipartite patella fibrous tissue become injured as part of their presenting injury and there may be micro-motion at this site, which contributes to having them have pain with lunging, squatting, and other type of stressful activities to the front part of the knee.
In those athletes who continue to have symptoms which really affects their function, consideration for an arthroscopic excision would be recommended. In those circumstances, the amount of the bipartite patella is usually not significantly contributing to their patellar function, so an excision would be recommended. It would be rare where there would be an open reduction and internal fixation of the bipartite patella and certainly this would significantly expand the rehabilitation program prior to returning back to activities.
9. Is a bipartite patella hereditary?
Bipartite patellas are probably a multifactorial genetic issue. While we do not know for sure if they are genetic, further studies may elucidate this more.
10. What is the recovery time for a bipartite patella injury?
The recovery time can vary significantly for treatment for a bipartite patella. If one has had no symptoms and has a bipartite patella injury, usually activity modification for 2-3 weeks will help to restore normal function. In those athletes who do require an arthroscopic excision, they are usually able to return back to full loading activities between 4-6 weeks after the arthroscopic excision.
11. How does one determine on MRI scan if a bipartite patella is symptomatic?
The best way to determine if a bipartite patella is symptomatic or not is on physical exam. If one is using the MRI to help determine if the bipartite patella is healed or not, any increased signal, which would indicate swelling, at the fibrous healing zone of the bipartite patella or the main portion of the patella may indicate that there is a higher risk that it is symptomatic. In contrast, if there is a bipartite patella with no increased signal at the scar tissue interface that forms between the bipartite patella and the patella, it would be much less likely that bipartite patella is symptomatic at that location. Other causes of the pain would need to be investigated, which could include chondromalacia within the bipartite patella portion.
12. What is the most common surgery for a bipartite patella?
In our hands, the most common surgery is an arthroscopic excision. With this surgery, the main portion, or most, of the bipartite patella is excised with a burr. We prefer this option because an open excision takes longer to recover and arthroscopically, one can preserve the lateral retinacular attachments to the patella, which could hinder one’s weightbearing status and activity level after surgery. An arthroscopic excision allows for early motion and early weightbearing and a return of activities once the quadriceps function is restored.
13. What is a pseudarthrosis in a bipartite patella?
A pseudarthrosis is a “joint” where motion occurs where there should not normally be one. In this case, the patella normally is one uniform bone throughout. However, if the bipartite patella portion that is formed with scar tissue becomes disrupted, there could be motion at this site. This is the pseudarthrosis portion.
14. What does a cyst mean when there is a bipartite patella?
Cysts in the patella usually form because there is some cartilage damage which causes fluid to leak up into the subchondral bone. Therefore, cysts in a bipartite patella may indicate some underlying osteoarthritis is present.
15. Does a bipartite patella always hurt?
Most of the time, a bipartite patella is an incidental finding on knee x-rays that are obtained in clinic. Because 1 out of 50 people have a bipartite patella, most cases of bipartite patella do not cause symptoms.
