Joint, Ligament and Muscle Disorders

Unstable Kneecap (Patella Instability) Procedures

Anatomy

The kneecap (patella) connects the muscles in the front of the thigh to the shinbone (tibia). As you bend or straighten your leg, the kneecap is pulled up or down. The thighbone (femur) has a V-shaped notch (femoral groove) at one end to accommodate the moving kneecap. A ligament on the inside (medial side) of the knee, called the medial patella femoral ligament (MPFL), also helps to hold the kneecap in place and to stop it from sliding/popping off of the outer side (lateral side) of the knee.

Symptoms

Symptoms of patella instability include: knee that buckles and can no longer support your weight, kneecap slipping off to the side, knee catches during movement, pain in the front of the knee that increases with activity, creaking or cracking sounds during movement, pain when sitting, stiffness, and swelling.

Causes

In a normal knee, the kneecap fits nicely in the femoral groove, allowing you to walk, run, sit, stand, and move easily. But if the groove is uneven or too shallow, the kneecap can slide off, resulting in a partial or complete dislocation. A sharp blow to the kneecap, as in a fall, can also pop the kneecap out of place. When this happens, the MPFL is usually torn and this makes it more likely for it to happen again. Once the kneecap slips (dislocates) out of the groove, problems such as recurrent dislocation and pain often result.

Diagnosis

During the physical examination, you may be asked to walk around or to straighten and bend your knee. Your orthopaedic surgeon may carefully feel the area around your kneecap and take measurements to determine if the bones are out of alignment or if the thigh muscles are weak. X-rays may be recommended to see how well the patella fits in the femoral groove. Other possible reasons for your pain, such as a tear ACL Injuries and Reconstruction Meniscal Tears PCL Injuries and Reconstruction in the cartilage or ligaments of the knee must also be eliminated.

Treatments

If the kneecap has been completely dislocated out of its groove, the first step will be returning the kneecap to its proper place. This process is called reduction. Sometimes, reduction happens spontaneously. If not, your doctor will have to apply gentle force to push the kneecap back into place.

A dislocation often damages the underside of the kneecap and the end of the thighbone, which can lead to additional pain and arthritis. Arthroscopic knee surgery may be needed to correct this condition.

When the kneecap is only dislocated, your doctor may recommend nonsurgical treatments, such as exercises to strengthen thigh muscles that help the kneecap stay aligned. Cycling is often recommended as part of the physical therapy, and a stabilizing brace may also be prescribed. Your goal will be to return to normal activities within 1 to 3 months.

A chronic condition, in which the kneecap continues to be unstable, can often be corrected by surgery. For example, surgery can be used to realign bone and repair or reconstruct the MPFL to keep the kneecap in place, or to release tissues that pull the kneecap out of the femoral groove.

VIDEO:Knee Injuries with Kirk Cousins & Dr. Bruce Stewart, Holland Hospital Sports Medicine

VIDEO:Dr. Bruce Stewart Knee Injuries in Athletes, Holland Hospital Physician Lecture Series, May 2015