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1089 Spadina Road
Toronto, AL M5N 2M7
Ph: 416-483-2654
Fax: 416-483-2654

Child Orthopedics
Spine - Cervical
Spine - Lumbar
Spine - Thoracic

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We are very frustrated because we have spent a great deal of money trying to help our daughter with a chronic knee problem. The problem is her left kneecap keeps popping off the to side (dislocating). Nothing she has tried has worked: taping, bracing, exercises, electrical stimulation, medications, etc. Are there any other choices left?

People who suffer one patellar (kneecap) dislocation after another search for ways to prevent this from happening. The obvious first question is: what is causing this to happen? Most often the patella pulls away from the knee in a lateral direction. Lateral means sideways in a direction away from the other knee. To better understand how this type of knee problem occurs, let's review a little bit of anatomy. The patella is held in place by its shape and the supporting soft tissue structures such as muscle, tendon, cartilage and ligaments. As the knee moves, the patella glides up and down in front of the knee joint. There is a groove on the front of the femur (the trochlear groove) of the femur. The back of the patella has a corresponding V-shape that fits inside the groove and helps hold it in place. Any changes in the shape of the bone, alignment, ligamentous laxity (looseness), muscle weakness, or other soft tissue problems can contribute to patellar instability. Usually finding the right treatment for this problem depends on identifying the underlying cause (or causes -- there are often multiple contributors). It's likely that your daughter has had X-rays and been examined by an orthopedic surgeon or sports medicine physician. If not, it might be helpful to go back to the beginning and figure out what brought this problem on and feeds into it's continuation. Interviewing the patient helps create a picture of what's happening and when it's occurring. The duration and severity of the problem will be revealed through this process. Next, the examiner performs an evaluation looking at motion, strength, alignment, tissue integrity, ligamentous laxity, position of the patella, and so on. One of the most accurate tests for patellar instability is called the apprehension test. In this test, the patient's patella is pushed to the side as the knee is bent. A positive response occurs if the patient's quadriceps muscle starts to contract during this movement or if the patient feels like the kneecap is going to pop off center and dislocate again. Patellar movement is also evaluated with the knee in full extension. X-rays are next. X-rays help show any unusual patellar shapes that might be part of the problem. There are special views that can be taken to show the position of the patella in the trochlear groove, the depth of the groove, and how well the two bones match up. In some cases of patellar instability, the patella is riding up above the groove. This condition is called patella alta. This is one of the many alignment factors that can put the knee at risk for dislocation. The radiologist also looks for the presence of the crossing sign on X-rays as an indicator of trochlear dysplasia. Trochlear dysplasia refers to a groove that is shallow -- too shallow to hold the patella in place as it glides up and down. The crossing sign is visible when looking at the knee from the side. It is a way to assess the depth of the trochlear groove. The treatment methods you described will often help someone with patellar instability that is caused by soft tissue imbalances and problems with postural alignment. But bony problems such as trochlear dysplasia may require something more permanent such as surgery. There are several different surgical approaches that can be taken. For example, the surgeon can perform a trochleoplasty. In this procedure, a piece of bone is removed from the trochlear groove and the area is deepened and reshaped. A different approach would be to use bone graft material to build up the lateral (outside) wall of the groove. Or the surgeon might change the rotational angle of the femur so the two bones (femur and patella) line up as they are supposed to. It may just be time to step back and reevaluate all that has been done, what has worked, what doesn't work, and why (or why not). If a comprehensive examination has not been performed, then this may be the next step. A second opinion is often encouraged when patients aren't making the kind of progress they expect or want.


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