MRI for Detecting Rapidly Progressive Knee OA: No Crystal Ball
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Knee osteoarthritis (KOA) typically develops over a decade or more. However, 1 in 5 people with KOA have more pain and disability at onset, have accelerated radiographic knee osteoarthritis (AKOA), and experience end-stage disease within 4 years. The use of demographics and clinical findings has resulted in only a 40% rate of correctly classifying patients who will develop AKOA instead of longer-term KOA.
Investigators recently conducted a case–control study using data from the OsteoArthritis Initiative (OAI), including demographic, clinical, and biochemical data, along with radiographic and magnetic resonance (MR) imaging data.1 The researchers hypothesized that the addition of an MR imaging-based scoring system would more accurately identify patients at risk for AKOA. They used classification and regression tree (CART) models to assess the ability of baseline MR features to classify participants who will develop AKOA and whether adding baseline MR features to an existing model improved classification of adults who will develop AKOA.
The existing model consisted of clinical data that included pain, function, physical exam findings, and quality-of-life measures. Demographic data included age, sex, and BMI collected at baseline. Biochemical data included high-sensitivity C-reactive protein and serum blood sugar. Data obtained from MR imaging scores included bone marrow lesion volume, effusion-synovitis volume, cartilage damage index, meniscal extrusion and degeneration, cruciate ligament degeneration, and patellar fat pad changes.
Contrary to the hypothesis, the CART models with and without MR features each explained approximately 40% of the variability. Adding MR-based features to the model improved specificity (0.90 vs. 0.82), but lowered sensitivity (0.62 vs. 0.70). Interestingly, the authors found that serum glucose, effusion-synovitis volume, and cruciate ligament degeneration were statistically important variables in classifying individuals who are likely to develop AKOA.
The clinical take home is that early MR data may be useful in sorting out mechanical complaints, but not in determining who will develop AKOA. In contrast, in later stages of KOA, MR images may reveal far greater damage than can be detected on radiographs.
- Price LL, Harkey MS, Ward RJ, MacKay JW, Zhang M, Pang J, Davis JE, McAlindon TE, Lo GH, Amin M, Eaton CB, Lu B, Duryea J, Barbe MF, Driban JB. Role of Magnetic Resonance Imaging in Classifying Individuals Who Will Develop Accelerated Radiographic Knee Osteoarthritis. J Orthop Res. 2019 Nov;37(11):2420-2428. doi: 10.1002/jor.24413. Epub 2019 Jul 29. PMID: 31297900