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Saturday, February 6, 1999

Isolated patellofemoral arthritis often overlooked

The severity of isolated patellofemoral arthritis, in the absence of severe tibiofemoral degenerative changes, is often overlooked by patients’ primary physicians due to the relatively benign appearance of the anteroposterior and lateral X-rays, according to a study reported in scientific paper 74 on Friday.

"It is obvious to orthopaedic surgeons and rheumatologists, but at times not to other health care providers overseeing these patients, that the confirmatory radiographic findings are most noticeable on the Merchant patellar tangential view, and that they may be completely masked on the standard anteroposterior and lateral views," said author Richard S. Laskin, MD, professor of clinical orthopaedic surgery, Cornell University Medical College, New York City.

A retrospective study was undertaken to evaluate the efficacy of total knee replacement in 53 patients with isolated patellofemoral arthritis (Group A) and compare the results with those seen in 46 patients with the more "traditional" tricompartmental arthropathy (Group B).

Dr. Laskin noted 16 patients in Group A had been followed by their primary care physician for many years without any specific evaluation of the patellofemoral joint either clinically or radiographically.

"In these patients the relatively benign appearance of the tibio-femoral joint led to prolonged, and in many cases, ineffective treatment for what was categorized as ‘mild knee arthritis,’" said Dr. Laskin. "Two patients had been advised to seek psychological counseling since the primary care physician advised them that there was ‘no arthritis on X-rays.’

"Yet patients had moderate or severe pain climbing stairs and marked difficulty riding in a car or getting out of a chair," he said.

Group A and B patients were matched for age (within five years) and sex. All underwent a cemented tricompartmental, posterior cruciate ligament retaining total knee replacement.

The mean preoperative flexion was 118 degrees in Group A; 114 degrees in Group B. "Thirty-two knees in Group A had a lateral tilt on a Merchant view X-ray (mean: 12 degrees) as compared to only three knees with a tilt in Group B (mean: 10 degrees). The mean Knee Society rating score preoperatively in Group A was 25, in Group B, 16. Before surgery, fewer patients in Group A than B were able to walk stairs a reciprocal manner.

At surgery, each knee in Group A had large areas of denuded cartilage down to a level of eburnated bone on the patellar and trochlear surfaces with associated periarticular osteophytes. "In each case," Dr. Laskin said, "the cartilage of the femoral condyles and tibial plateau showed, at most, Grade 1 chondromalacic changes."

When required, lateral release was performed from within outward with sparing of the lateral superior genicular artery. Fourteen knees in Group A and four knees in Group B required such a release.

Results of the study shows that Group A had better outcomes than Group B on knee score, pain relief and ability to walk stairs in a reciprocal manner. "According to the SF-36 evaluation, Group A also was more satisfied with their results," Dr. Laskin said. Range of motion and the ability to arise independently were similar between the two groups.

Patients were evaluated preoperatively, at six weeks, three months, one year and then biannually after surgery using a standardized multi-factorial computer database. Range of follow-up was 3 to 9.5 years (mean: 7.4 years). By year three, 48 patients remained in Group A.

At latest follow-up, the mean flexion in the Group A knees was 122 degrees; in the Group B knees, 117 degrees. The mean knee score in Group A was 96, in Group B, 88. Dr. Laskin said that 82 percent of the patients in Group A could reciprocate stairs whereas 72 percent could in Group B.

"Patellofemoral arthritis remains one of the more challenging problems for the orthopaedic surgeon," said Dr. Laskin. "It normally presents as anterior knee pain, exacerbated by stair climbing or arising from a chair. Most patients have little pain when walking on level ground."

The condition is often associated with retropatellar crepitus and pain with pressure on the patella during range of motion. The surgical options have included debridement, soft tissue releases, soft tissue or bony realignment, patellar osteotomy, patellar or combined patellofemoral prosthetic arthroplasty, and total knee replacement.

According to Dr. Laskin, extensor mechanism alignment procedures alone, whether proximal or distal, are often ineffective in the patient who has already developed advanced patellofemoral arthritis.

"Patellar debridement procedures, likewise, have a high failure rate when performed in the presence of extensive arthritic changes," he noted. "Replacement of both the patella and the trochlear groove, although slightly more successful, has still not proven to be effective for the majority of patients.

"Patellectomy for patellofemoral disease has a high failure rate," said Dr. Laskin. "It is difficult to recommend either patellofemoral replacement or patellectomy for the older patient with osteoarthritis, for whom there presently is tricompartmental total knee replacement which has an excellent success rate and survivorship."

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Last modified 06/February/1999