Distinct homogenous subgroups of patients with knee/hip osteoarthritis (OA) exhibit stable pain and physical function trajectories, according to study results published in Rheumatology.
The relationship between pain and physical function in OA is complex and interconnected. Using data from the Knee and Hip Osteoarthritis Long-term Assessment cohort (KHOALA; ClinicalTrials.gov Identifier: NCT00481338), investigators aimed to identify subgroups of patients with OA of the knee or hip with distinct trajectories based on the combination of pain and physical function over time.
Patients were followed up for 5 years, with pain and physical function assessed annually by questionnaires and medical examination at 3 and 5 years, respectively. A total of 807 patients (68.90% women; mean age, 61.90±8.49 years) were included in the study from the KHOALA cohort.
For both pain and physical function, 4 subgroups were identified, ranging from no pain or functional limitations to severe pain or functional limitations. Subgroups 1 to 3 included patients with severe, moderate, and low levels of functional limitations (n=95, 213, and 250, respectively), with 249 patients showing no functional limitation. While pain trajectories remained stable over time, trajectories of the functional limitation subgroups decreased over time. Concordance between pain and function trajectories was relatively low. Of the 95 patients in the severe functional limitation trajectory, 41% did not belong to the most severe pain trajectory. Similarly, 58% of the patients with severe pain did not belong to the subgroup with severe functional limitations.
From group-based modeling data, the researchers identified 4 distinct trajectories based on the severity of pain and functional limitation combined. The majority of patients (31.4%) were categorized into the low pain and functional limitation group, with 14.5% included in the severe pain and functional limitation group.
According to multivariate analysis, the group with severe vs no pain or functional limitation was associated with being women, older age, increased body mass index, high Kellgren and Lawrence radiologic grade, low physical activity intensity, and low vitality (P <.01 for all). High psychosocial distress was also associated with severe pain and functional limitation (P =.03). Similar trends were seen in the low and moderate pain and functional limitation groups.
At 5 years, 16.0% of patients underwent total knee arthroplasty or total hip arthroplasty. The percentage of patients who underwent surgery differed between groups, with higher percentages observed among patients with worse pain and functional limitation (P <.01).
Investigators noted that the subjective choice of the optimal number of groups represented a limitation of the study, as this could have led to heterogeneity across populations and studies.
“[O]ur multi-trajectory analysis identified  trajectories combining pain and [physical function] over a 5-year follow-up in patients with symptomatic knee and/or hip OA,” the researchers concluded. “The management of weight, fatigue, and psychosocial distress and the practice of physical activity seem important to maintain [physical function] and limit pain in patients with lower-limb OA.”
Disclosure: The KHOALA study was partially supported by the pharmaceutical industry. Several authors declare affiliations with the pharmaceutical industry. Please see the original reference for a full list of disclosures.
Wieczorek M, Rotonda C, Coste J, Pouchot J, Saraux A, Guillemin F, et al. Trajectory analysis combining pain and physical function in individuals with knee and hip osteoarthritis: results from the French KHOALA cohort [published online May 6, 2020]. Rheumatology (Oxford). doi:10.1093/rheumatology/keaa148