Dislocated Kneecap

A dislocated kneecap occurs when the kneecap (patella) pops out from its normal position. This can occur as the result of force, such as during contact sports. In many cases, however, a dislocated kneecap is related to a developmental condition that leads to an improper alignment of the kneecap with the thighbone (femur). This is sometimes called "unstable kneecap."

Kneecap dislocations typically occur in active teenagers and young adults from the ages of 14 to 20. They are most common in teenage athletes who participate in contact sports, such as football, and those suffering simple falls from a wide variety of activities, such as gymnastics, dancing, or cheerleading. They are also common in children with a family history of knee instability that leads to dislocation.

Each child may experience symptoms differently. The most common symptoms include:

• Pain in the front of the knee that increases with activity
• Swelling and/or stiffness
• Kneecap slips off to the side
• Difficulty using or moving the leg in a normal manner
• Deformity of the area around the dislocated kneecap
• Warmth, bruising, or redness in the injured area
• Creaking or cracking sounds during movement

Because the symptoms of a dislocated kneecap may resemble other conditions or medical problems, always consult your child’s doctor for a diagnosis.

The kneecap connects all the muscles in the thigh to the shinbone (tibia). As you bend or straighten your leg, the kneecap is pulled up or down. The thighbone has a v-shaped notch at one end to accommodate the moving kneecap.

In a normal knee, the kneecap fits nicely in the groove. However, if the groove is uneven or too shallow, if the ligaments are loose, or if there is a sharp blow to the knee, the kneecap could slide off, resulting in a partial or complete dislocation.

If you suspect your child has a dislocated kneecap, it’s important to have them evaluated by a pediatric orthopedic surgeon.

During the examination, the physician will obtain a complete medical history of your child. If the dislocated patella resulted from an injury, the physician may ask about how the injury occurred. The physician may ask your child to walk around or to straighten and bend their knee. The physician may also check the area around the kneecap and take measurements to determine if the bones are out of alignment or if the thigh muscles are weak.

Your child’s doctor will also want to eliminate other possible reasons for the pain, such as a tear in the cartilage or ligaments of the knee. X-ray or magnetic resonance imaging procedures may be used to view the knee to see how the kneecap fits into its groove.

Specific treatment for a kneecap dislocation will be determined by your child's physician based on:

• Your child's age, overall health, and medical history
• The extent of the injury
• The type of injury
• Your child's tolerance for specific medications, procedures, or therapies
• Expectations for the course of the condition
• Your opinion or preference

Non-surgical treatments

A dislocated kneecap may go back to its proper place on its own, but if it doesn't, your child's physician will need to gently push the kneecap back into its groove. Your child will receive sedation to remain comfortable and help the muscles around the dislocated joint relax so the joint can be put back into place more easily.

If the kneecap is only partially dislocated, the doctor may recommend non-surgical treatment. These include exercises to strengthen the muscles in the thighs that help keep kneecap aligned. A knee brace will immobilize the dislocated area to promote alignment and healing.

Surgical treatments

A dislocation can damage the underside of the kneecap and the end of the thighbone, which can lead to additional pain and arthritis. Arthroscopic surgery can correct this condition.

If your child’s knee continues to be unstable, their doctor may recommend a surgical procedure to realign and tighten certain tendons that help keep the kneecap on track or release tissues that pull the kneecap off track.

With proper treatment, your child should be able to return to normal activities within one to three months. It is important that they adhere to the activity restrictions and stretching and strengthening rehabilitation programs recommended by their care team to avoid future reinjury.

The Lower Extremity Program at Boston Children's Hospital offers comprehensive assessment, diagnosis, and treatment for children of all ages with conditions affecting their lower limbs. Our multidisciplinary team is made up of pediatric orthopedic surgeons and other clinicians who specialize in surgical and non-surgical treatments for dislocated kneecaps and a range of lower limb conditions related to trauma, congenital conditions, and developmental issues. With more than 7,000 pediatric visits per year, our team of lower extremity specialists is one of the most experienced in the country.

If your child is physically active and participates in contact sports, they may be more prone to having a dislocated patella. Our Sports Medicine Division is the largest and most experienced pediatric and young adult sports medicine practice in the country. Our team of sports medicine specialists combine personalized care with innovative treatment for each athlete we treat.

The Micheli Center for Sports Injury Prevention, part of the Sports Medicine Division, is dedicated to the prevention of sports injuries. Through research and clinical training, we offer practical strategies that help young athletes reduce their risk of injury while enhancing their sports performance. Our targeted rehabilitation and strength training programs help injured athletes return to play stronger and healthier.