Patients experiencing patellofemoral knee arthritis will have kneecap pain and stiffness and often swelling in the front part of the knee that typically worsens when walking on inclined terrain, going up and down stairs, squatting or rising from a seated position.
Patellofemoral arthritis is diagnosed when there is significant loss of cartilage from the joint surface of the patella and the trochlea (groove). The diagnosis is restricted to arthritis seen only in this compartment of the knee; if the medial and lateral compartments are affected, generalized osteoarthritis of the knee is the likely diagnosis. (As with other disorders of the patellofemoral joint, it is more frequently seen in women)
People who develop patellofemoral arthritis generally receive one of three diagnoses:
Treatment for patellofemoral arthritis always begins with non-operative measures. These include adaptations in activity, such as avoiding stairs, limiting squats and lunges, and decreasing impact sports; physical therapy to stretch and strengthen surrounding muscles; and use of medication such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve pain.
For patients with mild to moderate arthritis who are experiencing an acute flare of their condition with swelling, steroid injections, which reduce inflammation, can be effective. Good results are also being seen with viscosupplementation, in which a substance that mimics naturally occurring synovial fluid is injected into the joint to help lubricate it and minimize friction. In patients who are overweight, weight loss can help reduce the amount of stress applied to the knee. Bracing the knee is generally not helpful in people with patellofemoral arthritis.
People with patellofemoral arthritis who do not respond to nonsurgical treatment may be candidates for a partial knee replacement, also called a patellofemoral joint replacement or unicompartmental knee replacement. This procedure, allows the orthopedic surgeon to replace only the affected area of the knee, the patellofemoral joint, and to leave the healthy medial and lateral compartments intact. (Unicompartmental surgeries to address arthritis in each of those compartments are also an option for patients with arthritis in those portions of the knee.)
During this procedure the orthopedic surgeon removes the damaged cartilage and a small amount of bone from the joint surface of the patella and replaces it with a cemented high-density plastic button or patella implant. Damaged cartilage and a small amount of bone are also removed from the joint surface of the trochlear groove, which is replaced with a very thin, metal laminate which is cemented in place. “The goal is to eliminate friction and restore a smoothly gliding motion in the joint,” Dr. Beth Shubin Stein explains.
Orthopedic surgeons are now achieving excellent results with patellofemoral joint replacement, Dr. Shubin Stein notes, results that are comparable to those achieved with a total knee replacement.
In addition to partial knee replacement, patients with post-instability arthritis due to mal-alignment may also require soft–tissue procedures and/or osteotomy or tibial tubercle transfer surgery (described in the section on patellar instability) to realign the knee. This mitigates the possibility of subsequent dislocations. Patients who require more than one procedure may have them done either in stages or during a single operation.
“Determining whether the arthritis is the result of an alignment issue, or whether it is the beginning of an ongoing process that will eventually affect the entire knee is extremely important,” Dr. Sabrina Strickland notes. Patients who do best with patellofemoral joint replacement are those in whom the arthritis is not expected to progress: those with post-instability arthritis and those with post-traumatic arthritis, “These are patients who are unlikely to ever need a total knee replacement."
Many of the patients Dr. Strickland sees, are patients without a history of instability or trauma. They have isolated patellofemoral arthritis where it is likely the first or early presentation of osteoarthritis which may progress at some point to involve the rest of the knee. These are typically women in their 50s or 60s who experience pain and stiffness during certain activities and transitioning from sitting to standing. The knee is not painful with all activities and they are able walk on level surfaces without discomfort. While the symptoms are restricted to the patellofemoral compartment at the time of diagnosis, some arthritic changes may be observable in images of the rest of the knee.
“When I discuss surgical options with these patients, I let them know that although a patellofemoral knee replacement will address their symptoms, we can’t know with absolute certainty whether they will eventually require a total knee replacement. However, there are numerous advantages to the partial knee replacement, including a much faster recovery, and the sensation that the knee still feels ‘normal’,” Dr. Strickland notes.
For many of these patients, the promise of a decrease in pain and an improvement in function for years to come is acceptable. If a total knee replacement becomes necessary, their partial knee replacement will not compromise the results of this subsequent surgery.
Summary by Nancy Novick