Patellofemoral Instability
Patellofemoral Instability results from one or more dislocations or partial dislocations, also called subluxations. This misalignment can damage the underlying soft structures such as muscles and ligaments that hold the knee in place. Once damaged, these soft structures are unable to keep the patella (knee cap) in position.
Signs and symptoms of Patellofemoral Instability can include the following:
- Pain, especially when standing up from a sitting position
- Feeling of unsteadiness or tendency of the knee to “give way” or “buckle”
- Recurrent Subluxation: When the kneecap slips partially out of place repeatedly
- Recurrent Dislocation: When the kneecap slips all the way out of position repeatedly
- Severe pain, swelling and bruising of the knee immediately following subluxation or dislocation
- Visible deformity and loss of function of the knee often occurs after subluxation or dislocation
- Sensation changes such as numbness or even partial paralysis can occur below the dislocation as a result of pressure on nerves and blood vessels
Causes
Patellofemoral Instability can be caused by a number of factors that affect the way the patella moves along the groove of the femur (trochlear groove) when the leg is bent or straightened. The patella normally moves up and down with a slight tilt without touching the other knee bones. In Patellofemoral Instability the patella does not maintain its normal path of movement and can slip out of the trochlear groove either partially (subluxation) or completely (dislocation).
Diagnosis
Evaluating the source of Patellofemoral Instability is critical in determining your treatment options for relief of the instability. Your physician will perform the following:
- Medical History
- Physical Examination
- Diagnostic studies such as X-rays, CT scan, or MRI
The goal of conservative treatment for Patellofemoral Instability is to restore full range of motion by restoring the normal tracking pathway of the patella during flexion and extension of the knee. Treatment options may include closed reduction, pain medications, rest, ice, physical therapy, orthotics, and bracing. Surgical treatment of Patellofemoral Instability is sometimes necessary to help return the patella to a normal tracking path when conservative treatment options are unsuccessful
Patellofemoral Dislocation
Patella (knee cap) is a protective bone attached to the quadriceps muscles of the thigh by quadriceps tendon. Patella attaches with the femur bone and forms a patellofemoral joint. Patella is protected by a ligament which secures the kneecap from gliding out and is called as medial patellofemoral ligament (MPFL).
Dislocation of the patella occurs when the patella moves out of the patellofemoral groove, (called as trochlea) onto a bony head 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 of 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 discolouration 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 or conservative 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. Physiotherapist will extend your knee and applies 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-release – ¬It is done to loosen or release 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 cut using an arthroscope.
- Medial patellofemoral ligament reconstruction – In this procedure, the torn MPF ligament is removed and reconstructed using 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 individuals (autograft) or from a donor (allograft). This procedure is also performed using an arthroscope.
- Tibia tubercle realignment or transfer – Tibia tubercle is a bony attachment below the patella tendon which sits on the tibia. In this procedure the tibia tubercle is moved towards the center which is then held by two screws. The screws hold the bone in place and allow faster healing and prevent the patella to slide out of the groove. This procedure is also performed using an arthroscope.
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.
