Patellar Dislocation

Dislocation of the Patella

The patella, or kneecap, is the protective bone which lies in front of the knee joint. The patella bone glides up and down a groove (called the patellofemoral groove) at the front of the thigh bone (femur) as the knee bends. The patella is attached to the quadriceps muscle via the quadriceps tendon and acts to increase the leverage from this muscle group when straightening the knee.

The patella normally lies within the patellofemoral groove and is only designed to slide vertically within it. Dislocation of the patella occurs when the patella moves or is moved to the outside of this groove and onto the bony head of the femur (lateral femoral condyle). It is usually a result of an acute blow / twisting action of the knee. In most cases the patella will relocate the patellofemoral groove on straightening of the knee, however this is known to be extremely painful.

Factors leading to Patella Dislocation:

• Insufficient VMO strength - The VMO ( vastus medialis obliquus) functions in maintaining the patella in its desired position within the patellofemoral groove during knee movements by pulling it towards the middle of the knee joint- an action known as 'tracking'. If the muscle is not strong enough, or its fibers are not adequately oriented, the patella is much more susceptible to dislocation.
• Excessive pronation of the feet
• Q-angle - Some people have a larger than normal femoral angle (known as the Q-angle) and may have a 'knock-kneed' appearance (genu valgum). When the person straightens their leg, the patella will be forced to the outside of the knee. Thus any extra force applied to the inside of the knee may result in patellar dislocation.

Symptoms of Patellar Dislocation

• Swelling in the knee joint
• Pain around the patella
• Impaired mobility in the knee
• Obvious displacement of the knee cap

What the athlete can do?

• Apply RICE to the injured knee.
• Immediately seek medical advice.
• Rest from training.
• Wear a heat retainer or support.
• Take a glucosamine / joint healing supplement.
• Follow a rehabilitation program..

A Sports Injury Specialist or Doctor could

• Confirm the diagnosis - Patellar dislocations have similar symptoms to an anterior cruciate ligament injury, due to an audible 'crack or 'pop' and the feeling of the knee giving way
• Reduce the pain by anaesthetic and reposition the patella if it has not already relocated.
• Cyrotherapy (ice treatment)
• Exercises to strengthen the VMO
• Recommend NSAID's e.g. Ibuprofen to reduce pain and inflammation.
• Patellofemoral taping techniques
• Prescribe VMO strengthening exercises.
• Examine the injury by X-ray and/or arthroscopy to evaluate the extent of the injury.
• Operation may be necessary if there are loose fragments of bone or other major structural damage.