To state the obvious, the biologic factors underlying osteoarthritis (OA) are complex. Could one of those factors be a more important determinant of eventual OA and future total knee replacement surgery than previously thought?
A team of Ohio State University researchers designed a study to tease out the answers to that question. Their work, “Full-Thickness Cartilage Defects Are Important Independent Predictive Factors for Progression to Total Knee Arthroplasty in Older Adults with Minimal to Moderate Osteoarthritis: Data from the Osteoarthritis Initiative,” was published in the January 2, 2019 edition of The Journal of Bone and Joint Surgery.
Co-author Joshua Everhart, M.D., M.P.H. an orthopedic surgeon with the Ohio State University Wexner Medical Center described to OTW the rationale of his study. “I have frequently seen middle-aged patients in clinic with symptomatic knee osteoarthritis and minimal to moderate joint space narrowing on radiographs. Some do not respond well (or at all) to treatments such as activity modification or injections.”
“I often wonder why exactly these patients end up as non-responders to non-surgical OA treatments. In sports medicine practices we see that, in younger patients, high grade cartilage defects can be very symptomatic, even in an otherwise pristine knee. That made me think, ‘What if high-grade cartilage defects are a ‘hidden’ source of disability in middle-age patients with minimal to moderate OA?’”
To get the measure of high-grade cartilage defects in an OA knee, Everhart and his colleagues looked at data from 1,319 adults aged 45 to 79 years old who were enrolled in the Osteoarthritis Initiative (OAI). The data showed that 496 (37.6%) of the patients in the study had full-thickness cartilage defects. After analyzing the data, the researchers reported that knee arthroplasty incidence was 0.57% per person-year for adults without a full-thickness defect and 2.15% for those with a defect.
Dr. Everhart pointed out that “The OAI is a multicenter cohort study with very good long-term follow-up data on the natural history of knee OA in middle-aged adults. We looked at study participants that had none to moderate joint space narrowing on weight bearing radiographs and who also had knee MRIs upon study enrollment.”
“Keep in mind the MRI scans from this study were obtained for research only—the patients and their physicians were unaware of the MRI results. As it turns out, patients with full-thickness cartilage defects were several times more likely to have total knee arthroplasty within the study period. What I also found quite interesting was that full-thickness cartilage defects were a much better indicator of progression to knee arthroplasty than the degree of joint space narrowing on X-rays.”
“I do not advocate obtaining a knee MRI on every new patient with knee osteoarthritis. AAOS [American Academy of Orthopaedic Surgeons] guidelines for initial management of knee OA are appropriate and should continue to be followed. Weight bearing flexion PA [posteroanterior] radiographs should be obtained on any knee OA evaluation and first line non-operative treatments for OA treatments should be initiated.”
“However, in the subset of patients that don’t respond to non-operative treatment and do not have severe joint space narrowing, I would advocate surgeons to investigate further. There may be significant pathology (such as a full thickness defect) seen on MRI, and that patient may be well served by a surgical procedure. Total knee arthroplasty is obviously a well-established treatment for knee OA, but an osteotomy or unicompartmental arthroplasty are also good options for localized disease.”
“I would love to see additional research relating to optimized management of the middle-aged patient with poorly controlled knee OA symptoms but without severe joint space narrowing. I think this population is not well served in our current treatment algorithms and these patients are often advised their radiographic disease is ‘not bad enough’ to consider surgery.”
