The patella (knee cap) is a bone attached to the quadriceps muscles of the thigh by quadriceps tendon and to the shinbone by the patella tendon. The patella glides on the femoral groove and forms a patellofemoral joint. The patella is stabilized in its groove by a ligament called the medial patellofemoral ligament (MPFL).
Dislocation of the patella occurs when the patella moves out of the patellofemoral groove, (called the trochlea) onto a bony end of the femur. If the knee cap partially comes out of the groove, it is called as subluxation, and if the kneecap 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 lateral pull on the patella.
Some of the causes for patellar dislocation include direct blow or trauma, twisting of the knee while changing the direction, muscle contraction, and congenital defects. It 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 suggests diagnostic tests such as X-ray, CT scan, and MRI scan to confirm condition and provide treatment. There are non-surgical and surgical ways of treating patellofemoral dislocation.
Non-surgical treatment includes:
- PRICE (protection, rest, ice, compression, and elevation)
- Nonsteroidal anti-inflammatory drugs and analgesics to treat pain and swelling
- Braces or casts which will immobilize the knee and allows the MPF ligament to heal
- Footwear to control gait while walking or running and also decreases the pressure on the kneecap.
- Physical therapy is recommended which helps to control pain and swelling, prevent formation of scar of soft tissue, and also helps in collagen formation. Physiotherapists will extend your knee and apply direct lateral to medial pressure to the knee which helps in relocation. It includes straightening and strengthening exercises of the hip muscles and other exercises which will improve range of motion.
Surgical treatment is recommended for those individuals who have recurrent patella dislocation. Some of the surgical options include:
- Lateral-lengthening – It is done to loosen the tight lateral ligaments that pull the kneecap from its groove which increases pressure on the cartilage and causes dislocation. In this procedure, the ligaments that tightly hold the kneecap are lenghthened.
- Medial patellofemoral ligament reconstruction – In this procedure, the torn MPF ligament is reconstructed using grafting technique. Grafts are usually fixed to the femur and quadriceps tendon or patella. The grafts are either taken from the same individuals (autograft) or from a donor (allograft). This procedure is also performed using an arthroscope.
- Tibia tubercle realignment or transfer – The tibia tubercle is the bony attachment of the patella tendon on the tibia. If the knee is aligned with too much pull of the knee cap lateral, the tibial tubercle can be cut and moved towards the inside of the knee and held by two screws. The screws hold the bone in place and allow healing.
After the surgery, your doctor will suggest you to use crutches for 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.