The patella (knee cap) is a protective bone attached to the quadriceps muscles of the thigh by the quadriceps tendon. The patella attaches with the femur bone and forms the patellofemoral joint. The patella is protected by a ligament called the medial patellofemoral ligament (MPFL) which secures the kneecap and prevents it from gliding out of alignment.
Dislocation of the patella occurs when the patella moves out of the patellofemoral groove, (called the trochlea) onto the bony head of the femur. If the knee cap partially comes out of the groove, it is called a subluxation and if the kneecap completely comes out, it is called a dislocation (luxation). Patella dislocation is commonly observed in young athletes between 15 and 20 years of age and commonly affects women because the wider pelvis in females creates a lateral pull on the patella.
Some of the causes for patellar dislocation include a direct blow or trauma, twisting of the knee while changing direction, muscle contractions, and congenital defects. Dislocation also occurs when the MPFL is torn. 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.
Your doctor will examine your knee and suggest diagnostic tests such as X-rays, CT scan, and MRI scan to confirm the condition and determine the approach to treatment.
Medial patellofemoral ligament reconstruction – In this procedure, the torn MPF ligament is removed and reconstructed using a grafting technique. Grafts are usually harvested from the hamstring tendons, located at the back of the knee and are fixed to the patella tendon using screws. The grafts are either taken from the same individual (autograft) or from a donor (allograft). This procedure may be performed minimally invasive using an arthroscope.
After the surgery, your doctor will suggest you use crutches for a few weeks, prescribe medications to control pain and swelling, and recommend physical therapy which will help you to return to your sports activities at the earliest.