When arthritis strikes the knee joint, it can cause major disability. In fact, it is a leading cause of disability in the United States. Patellofemoral arthritis is a particular type of this condition that affects the patella bone, or kneecap. The pain generally arises in the front of the knee, making stair climbing and kneeling difficult for the patient.
Arthritis of the patellofemoral junction occurs when the cartilage within in the trochlear groove and on the underside of the patella break down. This causes inflammation in the joint. As cartilage wears away, the pieces of tissue fray, exposing the bone underneath can become exposed. The rough surface caused by the lack of this cartilage can make joint movement uncomfortable.
The kneecap is a small, triangular bone that resides at the front of the knee joint. It protects the juncture where the femur, or thighbone, meets the shinbone, or tibia. In addition to protecting the junction, it allows for muscles of the thigh to connect to the shinbone, facilitating movement.
On top of the knee joint is a small groove in which the patella rests. It glides back and forth within the groove when your knee bends and straightens.
To allow for this gliding, the groove that holds the patella, called the trochlear groove, the ends of the femur, and the underside of the patella are covered in articular cartilage. This flexible material allows for easy gliding of all the bones involved as you move your knee through its range of motion.
Fracturing the patella can cause damage to the articular cartilage on its underside or in the trochlear groove. Even when the bone itself heals, the cartilage may remain rough, causing friction. The friction occurs when the patella moves against the bottom of the femur, eventually leading to arthritis.
Another cause of this type of arthritis is dysplasia. It occurs when the patella doesn’t properly fit within the structure of the trochlear groove. Due to the lack of proper gliding, knee movement can put stress on the various articular cartilages. Of course, these stresses wear the cartilage down prematurely, causing arthritis.
Most patients experience patellofemoral arthritis as knee pain. Since the patella rests in the front of the knee, this is a common area to feel the pain. In addition, it can occur with activity or even at rest.
However, usually activities cause the most discomfort, especially movements that put pressure on the patella. This includes climbing stairs, squatting and kneeling, and getting up from a low chair.
Besides pain, you may experience a crackling in the knee, called crepitus by doctors. It occurs mostly when you move your knee, is often painful, and can be loud enough for another person to hear. In advanced cases of patellofemoral arthritis, the patella may catch when you try to straighten your knee.
Fortunately, the treatment of patellofemoral arthritis follows the same general course as treating knee arthritis of any kind. Most arthritis responds well to non-surgical treatment.
The first step in conservative treatment is non-steroidal anti-inflammatory medications, such as aspirin, ibuprofen, and naproxen. All of these medications decrease both pain and swelling.
In addition, exercise of the joint can decrease the stiffness you feel and help strengthen supportive muscles. However, you should avoid exercises that put stress on the front of the knee, such as squatting and high-impact exercise. Switching to low impact exercises, such as walking and swimming, can help to decrease pain from this condition.
Some patients find that simply avoiding movements, such as stair climbing, that aggravate symptoms is enough to manage the pain.
Another possible cause of pressure on the patella is carrying extra weight. Even a few pounds loss can greatly reduce the stress your knee takes with each step. Weight loss can not only help you move better, but it can help you retain your independence for as long as possible.
When these conservative measures are not effective, you may need to visit with a physical therapist to perform specific knee strengthening exercises. By strengthening the muscles of the thigh, you can take pressure off of the patella. When physical therapy causes pain, however, you need to inform your doctor and therapist for possible further intervention.
In some cases, a cortisone injection directly into the knee can help to decrease pain and swelling. This steroid mixture is a powerful anti-inflammatory and can provide long lasting relief.
Finally, a process known as viscosupplementation can ease the pain of patellofemoral arthritis by putting synthetic joint fluid into the space with the roughened cartilage, allowing the bone to glide in its groove more effectively.
Usually, surgical treatment is considered when non-surgical options fail or are not as effective. There are several different types of surgical interventions for patellofemoral arthritis.
Chondroplasty is a procedure done through arthroscopy. This approach means that the surgical instruments are inserted into inch long incisions around the sphere of the knee. With chondroplasty, your surgeon will trim and resurface roughened arrears of articular cartilage. Most mild to moderate arthritis responds well to this treatment.
Surgical realignment focuses on tightening or releasing tissue to either side of the patella. This helps the bone to slide more effectively in the trochlear groove by repositioning it.
In some cases, new cartilage may be needed, and this is known as cartilage grafting. The tissue is taken from another part of the knee or a tissue bank to repair the rough spots in the cartilage. In general, this procedure is only used on younger patients with small areas of damage.
A tibial tuberosity transfer can help with the discomfort some patients have in specific areas along the kneecap. The tendon holding the patella attaches to the front of the knee via an outcropping on the shinbone, known as the tibial tuberosity.
If this bulge is shifted, it will change the position of the patella, allowing it to move more smoothly in its groove. This will decrease both pressure on the knee and the pain from the arthritis.
Before a total knee replacement, your doctor may be able to perform a patellofemoral replacement. The worn bone and cartilage in the area is replaced by metal and plastic implants. In addition, the trochlear groove is fitted with a thin, metallic shield, and a dome-like implant is placed over the patella. Bone cement holds these prostheses in place.
Usually, if arthritis is present in other parts of the knee, a partial replacement isn’t a viable option for pain relief. This may mean you need a total knee replacement after a thorough examination and history with your orthopedic doctor.