Background/Purpose: Knee osteoarthritis (OA) is one of the leading causes of activity limitations among older adults. The course of activity limitations is highly variable; some patients seem to be stable or even improve, whereas others deteriorate. The aim of the present study was to identify subgroups of knee OA patients with different trajectories of activity limitations, and to describe patient characteristics for each subgroup.

Methods: Five-year follow-up data from a sample of 713 participants with early symptomatic knee OA from the Cohort Hip and Cohort Knee (CHECK) were used. Activity limitations were measured yearly with the physical function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Latent class growth analyses (LCGA) were used to identify trajectory classes of activity limitations. Multivariable logistic regression analyses were used to examine differences in demographic, clinical and psychological characteristics between the trajectory classes.

Results: The LCGA yielded 3 trajectory classes for activity limitations. Participants in class 1 (‘slight limitations’; n = 336) reported permanent low levels of activity limitations, or moved from moderate or high levels at baseline to low levels of activity limitations over 5 years. Participants in class 2 (‘moderate limitations’; n = 261) reported permanent moderate levels of activity limitations, or moved from fairly high or fairly low levels to moderate levels of activity limitations over 5 years. Participants in class 3 ( ‘severe limitations’; n = 116) reported permanent high levels of activity limitations, or moved from low or moderate levels of activity limitations to high levels of activity limitations over 5 years. Participants in class 1 (‘slight limitations’) were more likely to have a lower BMI, to have less than 3 comorbidities, to report a lower level of knee pain, no to have hip pain, not to have joint space narrowing, and to feel more vital, compared with participants in class 2 (‘moderate limitations’) (AUC: 0.75). Participants in class 3 (‘severe limitations’) were more likely to report a higher level of knee pain, to have bilateral knee pain, to have osteophytosis, to feel less vital, and to avoid physical activities (AUC: 0.76).

Conclusion: Three trajectory classes of activity limitations were identified using 5-year follow-up data of 713 participants with early symptomatic knee OA: ‘slight limitations’; ‘moderate limitations’; and ‘severe limitations’. The ‘slight limitations’ group was characterized by a lower BMI, a lower comorbidity count, lower levels of knee pain, not having hip pain, not having joint space narrowing, and high vitality. The ‘severe limitations’ group was characterized by higher levels of knee pain, bilateral knee pain, osteophytosis, low vitality, and avoidance of physical activities.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/three-trajectories-of-activity-limitations-in-early-symptomatic-knee-osteoarthritis-a-5-year-follow-up-study/