The patella (knee cap) is a bone at the front of the knee. It is attached at the top to the quadriceps muscles of the thigh by quadriceps tendon. A strong tendon then attaches the bottom of the patella to the top of the tibia (shin bone). When you contract your quads, the patella is pulled up and pulls on the tibia, straightening the leg. The patella slides over the end of the femur (thigh bone) forming the patellofemoral joint. This is a groove in which the patella moves. Structures to the side of the patella ensure it stays within the groove. An important structure is medial patellofemoral ligament (MPFL) which prevents the patella sliding out to the outside of the knee.

What is Patellar Dislocation?

Dislocation of the patella occurs when the patella moves out of the patellofemoral groove, (called the trochlea) onto the outer edge of the of the femur. If the patella partially comes out of the groove, it is called as subluxation and if the patella completely comes out, it is called as dislocation (luxation). Patella dislocation is commonly observed in young athletes between 15 and 20 years and commonly affects women because the wider pelvis creates a lateral pull on the patella.

The common symptoms include pain, tenderness, swelling around the knee joint, restricted movement of the knee, numbness below the knee, and discoloration of the area where the injury has occurred.