The patella, or kneecap, is the small bone in the front of the human knee joint. The patella is a type of bone called a sesamoid bone, and it is the largest sesamoid bone in the body. It serves to improve the line of pull of the quadriceps muscle in the front of the thigh. The patella resides in a small groove at the end of the thigh bone. When the patella becomes dislocated, or moves out of its groove, it causes knee pain and loss of proper knee function.
Types of Dislocations
There are two types of dislocations in the human body: dislocations and subluxations. A dislocation occurs when a joint moves out of place and stays out of place. If your patella moves out of its original position and stays out of position, then a dislocation has occurred and immediate medical attention is required to relocate, or reduce, the dislocation. A subluxation is when your patella moves out of position and then quickly and spontaneously moves back into position.
Causes of Patella Dislocation
The patella may become dislocated during athletic activity when the knee is twisted in an unnatural position and the foot is firmly planted on the ground. For instance, if you are playing soccer and your foot is planted on the turf and then your knee becomes twisted, the patella may be pulled out of position and become subluxed or dislocated.
Another cause of patella dislocation is if you suffer a forceful blow to the knee in a sideways direction. This force can push the patella out of position.
Occasionally, tight or weak muscles around the knee and hip may cause the patella to dislocate or sublux. Tightness in the iliotibial band may pull the patella abnormally. Weakness in the quadriceps muscle that controls patella position may result in improper patella position and subluxations. Sometimes subluxations may occur for no apparent reason and you may suffer episodes where the patella quickly subluxes and then is repositioned. Each episode of subluxation is painful, and multiple episodes may become worse with the passage of time.
First Aid for a Dislocated Patella
If you have knee pain and suspect you have dislocated your patella, first follow the R.I.C.E. principle to minimize swelling and control inflammation around the knee. Then, check the position of your patella. Most often the patella moves towards the outside, or lateral, part of the knee. If your patella is clearly out of position, a visit to your local emergency department or doctor is recommended to have the dislocation reduced. You may be given crutches to walk with for a few days or weeks while healing occurs, and you may work with a physical therapist to learn how to walk with the crutches.
It is not a good idea to try to reduce the patella on your own, as other muscles or tendons may be injured, and further injury may result if you attempt such a maneuver.
If your patella appears to be in its normal position, then you may have simply subluxed your patella. Follow the R.I.C.E. principle for two to three days, and visit your doctor or physical therapist to have the knee examined.
What to Expect from Physical Therapy for a Dislocated Patella
If you have a dislocated patella, your doctor may refer you to a physical therapist for evaluation and treatment of your knee. If you wish, you may be able to self-refer to physical therapy via direct access.
During your initial appointment in physical therapy, be prepared to explain to your physical therapist the nature of your symptoms. Do you have pain? Does your knee feel weak or does it give out? Is your knee swollen? How does your knee pain affect your daily activities like work or recreation? Answering these questions may help your physical therapist in developing the correct treatment for you.
Your physical therapist may also take certain measurements of your knee to help decide on the proper treatment. Components of the physical therapy evaluation may include a gait evaluation, range of motion measurements, strength measurements, measurements of swelling, and special tests. Your therapist may also assess the amount of motion around your patella to determine if it is loose or hypermobile.
Physical therapy treatment for a dislocated patella can begin after the initial evaluation. Common physical therapy treatments may include modalities to control pain and swelling, treatments to improve muscle contraction and function around the patella, and gait training to improve walking.
The quadriceps muscles on the top of the thigh help to control the position of the patella, and this muscle group may be weak if you have suffered a patella dislocation. Knee exercises to help improve contraction of this muscle group may be started once pain and swelling allow.
Most current research indicates that hip weakness may also play a role in causing a dislocated or subluxed patella, so hip strengthening exercises may also be incorporated as part of a physical therapy program. Advanced hip strengthening may be required after a few weeks to help prepare to return to normal activity and athletics.
There are also taping techniques that many physical therapists use to help control the position of the patella. The general thought with taping is that the tape holds the patella in the proper position while the muscles around the knee "relearn" how to work properly to hold the patella in position.
Knee braces may also be used to help control the position of the patella to help prevent dislocations or subluxations. Caution must be used not to overuse the brace. This may create dependence on the brace, and the muscles and tendons that support the patella may become weakened and may not be able to help provide proper support. Generally, braces should be used for athletic activity or for specific functional activity like walking or for yard work. Once you are in the house and relaxing, the brace should be removed.
After four to eight weeks of treatment for your knee, you should be relatively pain-free and your knee should be functioning properly. Of course, the time necessary to fully heal depends on many factors, such as the severity of your injury, your age, and your health status. If you continue to experience knee pain due to subluxations or dislocations, you should visit your doctor to discuss other options. Occasionally a surgical procedure called a lateral release is necessary to correct the problem and prevent the kneecap from dislocating. If you do require surgery, physical therapy after surgery may be ordered to help you regain normal knee function.
A dislocated patella can be a painful thing. It can limit your ability to walk, run, or participate in recreational activities. A physical therapy program may help you regain normal knee function and may help to prevent future episodes of patella dislocations.
Safran, M., Stone, D., & Zachazewski, J. (2003). Instructions for sports medicine patients. Philadelphia: Saunders.