Patellar Dislocation and Instability
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Overview
Your kneecap (patella) is usually resting in a groove at the end of the thighbone (femur). When the knee bends and straightens, the kneecap moves straight up and down within the groove, similarly to a train running on a track. Sometimes, the kneecap slides too far to one side or the other. When this occurs, the kneecap can completely or partially dislocate.
When the kneecap slips out of place, whether a partial or complete dislocation, it typically causes pain and difficulty moving the knee. Even if the kneecap goes back into place by itself, it will still require treatment to relieve painful symptoms. Be sure to go to the doctor for a full examination and be referred to an Orthopaedic Surgeon who is skilled in knee disorders, to identify any damage to the knee joint.
Description
There are a several ways in which the kneecap can become unstable or dislocate. In many cases, the patella dislocates with very little force because of an abnormality in the structure of the knee. A shallow or uneven groove in the femur can make dislocation more likely. Some people’s ligaments are looser, making their joints extremely flexible and more prone to patellar dislocation. This occurs more often in girls, and the problem may affect both knees.
In those with normal knee structure, patellar dislocations are often the result of a direct blow or a fall onto the knee. This incidence is more common in high-impact sports, such as football. Dislocations can occur without contact as well. An example is that of a right-handed baseball player who dislocates the right patella while swinging the bat. When the right foot is planted on the ground and the torso rotates during the swing, the patella lags behind, resulting in dislocation.
Symptoms
The symptoms associated with a patellar dislocation depend on how far out of place the patella has moved and how much damage occurred when it happened.
Some general symptoms include:
Pain
Feeling the kneecap shift or slide out of the groove
Feeling the knee buckle or give way
Hearing a popping sound when the patella dislocates
Swelling
A change in the knee's appearance - the knee may appear misshapen or deformed
Apprehension or fear when running or changing direction
Over time weakness of the knee will occur and patients will avoid activities which provoke dislocation to occur
Imaging
Imaging tests can help diagnose patellar instability, as well as determine a treatment plan.
X-rays
These tests create clear pictures of bone. These are useful to look for skeletal abnormalities in the knee, such as a shallow groove in the femur.
Magnetic resonance imaging (MRI) scans
These scans create better pictures of the soft structures surrounding the knee, like ligaments. An MRI is very useful in assessing the cartilage and ligaments, which are commonly damaged during patella dislocation
CT Scans
These are very useful for looking at a patient’s rotation, which can be a significant contributing factor in patellar dislocation.
Treatment
If the patella remains dislocated, it needs to be put back in place by a doctor as soon as possible.
Nonsurgical Treatment
Your surgeon will advise you regarding the use of braces, weight bearing, crutches and a specific physiotherapy program depending upon the cause of the patellar dislocation.
Because a dislocation damages knee ligament, the patella often remains looser, or more unstable, than it was before the injury. As a result, the patella can dislocate again, often with less force than the first episode. Recurrences also are common if the dislocation was caused by an abnormality in the knee structure.
Surgical Treatment
If your knee has sustained injury to the cartilage or if the patella dislocates multiple times, surgery may be recommended to correct the problem. The type of surgery will depend on the cause of the unstable kneecap. These is a wide variety of surgery available to treat patellar dislocation, which our surgeons are able to utilise to treat the exact cause of the dislocation. Our surgeons are skilled in minimally invasive techniques of ligament reconstruction, femur realignment and arthroscopic techniques to treat patellar instability which they will discuss with you during your consultation.
