clock menu more-arrow no yes mobile

Filed under:

The Injury Clinic - The O'Dowd Injury

When I saw Kris O'Dowd bend backwards the way he did I immediately thought torn ACL with a possible MCL injury. Turns out I was wrong and I'm not sure if that is good news or not. ACL injuries in athletes that are surgically repaired are a well-proven and a time tested surgery. Many athletes have had the procedure and went on to have successful careers. The patella dislocation is another matter. This is not as common as the ACL injury in athletes but an ACL injury must be ruled out and that can be done with a number of different tests. Surgery is not indicated unless the injury is recurrent and is usually a last resort.

Treatment for this injury obviously depends on how severe the injury is, but special care is taken to strengthen the Vastus Medialis of the Quad Muscle structure. This muscle helps to place a medial pull on the patella, reducing the lateral, dislocating force.

Here is a little anatomy and physiology from the Athletic Advisor:

The Dislocated Patella
The patella (knee cap) is a sesamoid bone. A sesamoid bone is one that is encased in tendon or ligament. The patella is located inside the quadriceps tendon. The patella acts as a fulcrum to increase the strength of the quad muscle. It is held in place by the quadriceps tendon above, the patellar tendon below, and very thin ligaments on either side. The patello-femoral joint is formed by the patella and trochlear groove of the femur.

Due to the twisting nature of sports, the patella can dislocate (come out of joint) with an awkward twist of the femur (thigh) on the tibia (shin). A twisting motion causes the patella to shift to the side. Usually, the patella moves laterally (to the outside). This occurs because the quadriceps muscle contracts to maintain the stability of the body. The shin has shifted so that the line of pull of the quads causes the patella to shift laterally. The patella is pulled laterally because it wants to remain in line with the muscle.

The patella can dislocate more easily in some people than others. Individuals with a greater "Q-angle" are at a greater risk for patellar dislocations. The "Q-angle" is formed by envisioning a circle around the patella, the line of pull of the quad muscle forms the tail of the "Q." If the tail of the "Q" is more than 25 degrees off of the center of the quad-patella-patellar tendon line of pull, it is considered an abnormally high "Q-angle."

This places the patella at a greater risk to slide off of the femur. The quad-patella-patellar tendon mechanism wants to form a straight line when the quad muscle contracts, due to this, the patella is pulled laterally. This places a person with a high "Q-angle" at a greater risk for patellar dislocations.

Another risk factor for patellar dislocations is a malformed patella or trochlear groove (the groove located between the two heads of the femur) . The back side of the patella should have a peak, like an inverted mountain top. The trochlear groove should look like the valley between mountains. If either the mountain or the groove are not large enough, the patella is more prone to dislocate.

This is demonstrated by the x-ray. The back side of the patella is flat. This accounts for the sideward lean of the patella. This patella is prone to dislocate and is partially dislocated or subluxed in the x-ray. X-rays are necessary to rule a fracture of the patella. In some cases the mountain peak of the patella will be "knocked off" when it impacts with the femur. This piece of bone can cause severe damage to the joint if it is not properly addressed.

The retinaculum is the band of connective tissue that attaches to the medial and lateral structures of the knee joint, including the patella and patellar tendon. In a patellar dislocation this is either stretched or torn.

The "Sunrise" view of the Knee
Images from Kyle Palmer, MD
If an athlete suffers a patella dislocation that does not spontaneously reduce (go back into place), it is rather obvious to detect. The patella will be laying near the outside of the knee joint. However, it is quite common for the patella to spontaneously reduce. Many times the athlete will straighten his/her leg inadvertently after the injury, causing the patella to reduce.

If the patella has been reduced, the athlete will present with increased pain, swelling, and loss a decrease in range of motion of the knee. The swelling may be great enough as to make the patella "disappear." Due to the swelling, the patella may also feel, when pressed straight down, as if it is a boat floating in water.

The swelling is due to tearing of the ligaments on the medial side of the patella. This swelling is located inside of the joint, accounting for the patella feeling like a floating boat. Since this injury usually results from a twist, and the swelling is located inside of the joint, an orthopaedic surgeon should be consulted to differentiate between a dislocated patella and an ACL tear.

Non-surgical treatment of the dislocated patella is as follows:

  • Patients will usually be required to keep the knee stabilized for up to six weeks. The doctor will prescribe either a brace or splint to prevent further damage.
  • After the splint or brace is removed, physical therapy will be initiated to restore strength and correct alignment problems or muscle imbalances that may have contributed to the dislocation.
  • The goal of therapy is to re-establish a full range of motion in the knee with proper alignment or tracking of the patella.
  • Ongoing therapy rehabilitates the quadriceps and hamstrings, the muscles surrounding the knee which add strength and stability to the joint.
  • Therapists may recommend changes in activity and specialized bracing to support the knee during movement or while it is under stress.
From the Kerlan-Jobe Clinic