Men's Sports

Sports Docs Weekly Blitz: The knee cap

What about the kneecap?

In an earlier blog, I wrote about true knee dislocations such as the recent Teddy Bridgewater injury. Patella (kneecap) dislocations are not nearly as severe of an injury, yet they still remain a significant problem requiring weeks of rehab.

Patellar dislocations are almost always associated with a shift of the kneecap to the outer side of the knee (lateral). The anatomy of the kneecap joint dictates this. In addition, it is more common that an athlete takes a blow to the inner side of the kneecap that leads to a lateral shift. A strong twisting injury to the knee can also dislocate the patella.

Here’s a clinical photo of an athlete with a dislocated left patella.


The kneecap normally glides in a groove in the end of the thigh/femur bone. The patella is supported by ligaments along its inner and outer margins. The medial ligament has a thickening called the medial patello-femoral ligament.

Try saying that four times quickly!

This medial ligament is also called the MPFL. If the MPFL is ruptured with a patellar dislocation there is a greater chance the athlete’s knee will have recurrent dislocations.

This is an X-Ray of a normal kneecap joint (patello-femoral joint), the so called sunrise view.


The X-Ray view of a dislocated patellar looks like this:


Below is an MRI image with a ruptured Medial Patella Femoral Ligament (MPFL):


The displaced ligament can sheer off cartilage or bone and cartilage fragments into the joint.


If there are no fragments in the joint and the ligaments are stretched but not ruptured, the treatment is a straight leg immobilizer for 3 weeks followed by physical therapy to strengthen the quad muscles which stabilize the kneecap. Even with optimal treatment, there is a chance for recurrent dislocations.

If there are fragments in the joint or a highly unstable kneecap, surgery is recommended. With arthroscopic visualization, the fragments can be removed and the donor site smoothed with special instruments. A small incision is needed to repair the MPFL.

At ISU, many patellar injuries are subluxations (partial dislocations) that can be treated with immobilization and rehabilitation with the athletic trainers at the Bergstrom Football complex. Mark, Shannon and Nate get the athletes back to action in record time!

Go Cyclones!


Dr. Peter Buck