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Patellar crepitus: A nagging but treatable problem related to posterior-stabilized TKR
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A survey of 428 patients conducted more than 1 year after they underwent total knee replacement with one of two posterior-stabilized knee implant designs revealed a 24% rate of patellar crepitus among both prostheses, with patients reporting symptoms of crunching, grinding and grating.
Crepitus with posterior-stabilized total knee replacement (PS TKR) is a reality orthopedic surgeons may need to address with their primary surgical technique or in subsequent procedures, said Mark W. Pagnano, MD, an investigator at the Mayo Clinic in Rochester, Minn., involved with the survey.
“For most of the patients, however, the crepitus was neither painful nor audible,” Pagnano said.
Related etiology
Pagnano said crepitus is caused by the same conditions responsible for patellar clunk: frank catching of a synovial nodule in the intercondylar box during knee extension.
Patellar clunk practically disappeared after better implant designs were introduced that provided a smoother transition between the implant’s intercondylar box and trochlea.
Treatment for crepitus consists of open surgery or arthroscopic debridement and is indicated for persistent symptoms or pain, he said.
“Symptoms of grating, grinding, crunching — what we can collectively term ‘crepitus’ — continue to be reported in a subset of modern PS total knee patients,” according to Pagnano. “In the future, we’ll look to design changes to eliminate this problem.”
Survey results
To understand why patellar crepitus develops after PS TKR in some people, Pagnano and colleagues surveyed by telephone and mail 599 patients who had PS TKR surgery with either a Sigma PS (DePuy) or NexGen Legacy LPS (Zimmer) femoral prosthesis. All of them participated in previous randomized trials for their TKR prostheses and could readily be reached for the survey, he said.
Four hundred twenty-eight individuals completed and returned the survey (177 patients with the Sigma and 251 patients with the Legacy designs; mean age 67 years). The survey asked specifically about patellofemoral problems, Pagnano said.
In addition to a 24% rate of patellar crepitus in both groups, “Symptoms most often appeared in the first year after the total knee, but one-fifth of cases occurred after 1 year,” he said.
Some dissatisfaction
Survey results showed crepitus issues usually did not affect patient satisfaction with TKR surgery. “However, there was a small subset of patients who were markedly dissatisfied because of the crepitus,” Pagnano said.
In 25% of the patients, patellar crepitus symptoms disappeared about 1 year after onset, but two patients eventually needed arthroscopic debridement to resolve them. Investigators noted no difference among the symptoms patients reported based on the type of PS TKR implant they had.
To prevent crepitus, Pagnano performs a superpatellar synovectomy during the primary TKR to remove the problematic synovium, trying not to elevate the joint line or leave the patella so thin that it might encroach on the intercondylar box.
“Surgical treatment, when it is necessary, is going to be similar to classic patellar clunk. You can expect about 80% success,” he said.
For more information:
- Mark W. Pagnano, MD, can be reached at the Mayo Clinic, 200 First St. SW, Rochester, MN 55944, U.S.A.; +1-507-284-5276; e-mail: pagnano.mark@mayo.edu. He receives royalties from DePuy, a Johnson & Johnson Company, and Zimmer Inc.