Arthritis of the Knee: Patellofemoral Joint
The knee may be divided into three parts or compartments: the inner or medial side, the outer or lateral side and the front or anterior part, which is composed of the patella (knee cap) joined to the femur (thigh bone). The latter, also called the patellofemoral joint, is involved in many activities like going up and down the stairs, kneeling, squatting and rising from a sitting position. The other 2 compartments of the knee joint are more involved in walking on a flat surface.
Arthritis of the knee may involve one or more of the three compartments of the knee. Arthritis of the patellofemoral joint is often seen in women in their third and fourth decades of life. It usually involves both knees, and may be due to overuse, patellar instability and degeneration. It is manifested as knee pain, swelling, clicking and stiffness, and is aggravated when walking on an inclined terrain, going up or down the stairs and when standing up from a prolonged sitting position. Knee pain is usually absent when walking on flat ground.
Diagnosis is confirmed by x-ray and MRI imaging, where a loss of cartilage in the front part of the knee joint is seen.
Non-surgical treatment consists of anti-inflammatory medications and physical therapy. When degenerative changes are mild, release of tight tendons and joint preserving procedures may be done surgically. However, in older patients who have significant cartilage loss and a “bone on bone” disease a knee joint replacement may be indicated.
Patellofemoral Joint Replacement Surgery
Severe knee joint pain is usually treated by performing a total knee replacement. However this is done only for those with involvement of the whole or most of the knee joint.
For people whose arthritis is limited to the anterior (front) part of the knee, a partial knee replacement or patellofemoral joint replacement surgery is more suitable. It preserves the other normal parts of the knee and does not result in limitation of motion as does the total knee replacement.
In this procedure the surfaces of the patella and femur which are affected by degenerative changes are replaced with a prosthesis which is made of plastic and metal. This material provides a smooth surface in which the bony parts can glide smoothly at the same time resisting wear.
Patellofemoral joint replacement is ideal for older patients, especially those who have multiple health problems because it is not an invasive procedure. Perioperative blood loss and infection are less likely to occur and hospital stay is not prolonged. It also allows a great range of motion than if the whole knee joint were replaced.
If done in younger patients it has the advantage of ease of later revision as needed compared to a total knee replacement.
Since arthritis is a degenerative disease that comes with age and overuse of joints, progressive loss of cartilage may occur throughout the rest of the knee. The only disadvantage of the procedure is that for some, the need for revision later in life (around 10 years) may not be practical, especially when the patient has grown older and has acquired other health conditions. This is the reason why others may opt for a total knee replacement.
The procedure lasts for about 90 minutes and the patient is discharged after a couple of days. For the best outcome the patient is advised to undergo physiotherapy for 6 weeks to 3 months.
Surgical risks include:
- Bleeding and thrombosis (blood clotting)
- Implant infection
- Delayed wound healing
- Wear and loosening of the implant
- Nerve damage
Since partial knee replacement surgery is relatively less invasive than total knee replacement, there is lower risk of perioperative complications.
Hospital for Special Surgery, “Patellofemoral Arthritis in the Knee: An Overview” accessed 1/18/11
Sports Orthopaedics UK, “Patellofemoral Surgery”, accessed 1/18/11