By Chris Klingenberg
Age and body mass index (BMI)—as well as their interactions with glucose concentration and static femorotibial alignment—contribute to increased risk of accelerated knee osteoarthritis (OA), according to research from Tufts University School of Medicine in Boston that could have implications for early diagnosis and intervention in this population.
People who develop knee OA earlier than expected and in whom the disease progresses very quickly are said to have “accelerated” knee OA; because the window of opportunity for early intervention in these patients is very small, the ability to screen for potential risk factors is even more critical than in the typical knee OA population (see “The clinical implications of accelerated knee OA,” April 2016, page 43).
“This study is a nice reminder that there can be complex interplay among risk factors for things like accelerated knee osteoarthritis,” said Jeffrey Driban, PhD, ATC, CSCS, who is an assistant professor in the Division of Rheumatology at Tufts University School of Medicine and also on the scientific staff at Tufts Medical Center. “This interplay is important because it may help identify high-risk groups of adults and may eventually lead to targeted prevention strategies.”
Driban and colleagues conducted a case-control study that used data and images from baseline and the first four years of follow-up in the Osteoarthritis Initiative, a longitudinal multicenter observational study of adults with or at risk for knee OA. The Tufts study population included 54 patients diagnosed with accelerated knee OA (defined as advanced-stage OA onset within four years) and two control groups, each with 54 individuals; one control group included patients with typically developing knee OA, and the second control group included individuals without knee OA.
The authors then used a classification and regression tree analysis to assess eight risk factors for typically developing knee OA in terms of their association with accelerated knee OA: serum concentrations for C-reactive protein, glycated serum protein, and glucose; age; sex; BMI; coronal tibial slope; and femorotibial alignment.
Age and BMI were both independently associated with accelerated knee OA. Age may be the most important factor for classifying those at high risk, the study found—but with some exceptions. Individuals younger than 63.5 years were unlikely to develop accelerated knee OA unless they were obese (BMI ≥ 33.9 kg/m2). Individuals older than 63.5 years were classified as being at risk for accelerated knee OA except when they had elevated fasting glucose concentrations (> 81.98 mg/dl) and no varus malalignment (femorotibial angle ≥ 2.31°); BMI did not seem to play a role in the older group. The findings were epublished in August by the Journal of Orthopaedic Research.
However, Driban noted that the four contributing factors identified in the study—age, BMI, glucose level, and femorotibial alignment—only accounted for 31% of the variance in the analysis.
“Our analysis suggests we’re missing a lot of information that may help classify people at risk for accelerated knee OA,” he said. “For example, injuries are likely an important factor. Our preliminary findings suggest that injuries that compromise the subchondral bone or the function of the meniscus are especially concerning.”
Abbey Thomas-Fenwick, PhD, ATC, an assistant professor in the Department of Kinesiology at the University of North Carolina at Charlotte, noted that factors other than those examined in the Tufts study also can play a role in typically developing knee OA.
“Knee joint injury represents an important risk factor for knee OA, leading to what is known as posttraumatic OA. This phenotype of the disease tends to present in younger individuals following injury to the joint,” she said. “Genetics may also play a role, as some individuals are inherently susceptible to OA development.”
Driban JB, McAlindon TE, Amin M, et al. Risk factors can classify individuals who develop accelerated knee osteoarthritis: data from the osteoarthritis initiative. J Orthop Res 2017 Aug 4. [Epub ahead of print]