Background/Purpose:  Pain and disability related to osteoarthritis (OA) may generally be considered to be chronic, but it is known that its course can be very different between patients.  In this study, it is investigated whether there is a difference in course of pain,  physical function and radiographic damage during follow-up between two OA cohorts: Osteoarthritis Initiative (OAI) and Cohort Hip & Cohort Knee study (CHECK).

Methods: For the current study, longitudinal data of four years follow-up of the CHECK study and OA Initiative were used. The CHECK study is a Dutch prospective 10-year follow-up study, initiated by the Dutch Arthritis Association, to study progression of OA in participants with early symptomatic OA of knee or hip. Individuals were eligible if they had pain of knee or hip, were aged 45-65 years, and had not yet consulted their physician for these symptoms. In the same time in the U.S. an observational 4-year follow-up study was started to create a public archive of data, biological samples and joint images to study the natural history of, and risk factors for, the onset and progression of knee OA. The WOMAC was utilized to measure pain during activities (range 0-20) and physical functioning (range 0-68). For comparison with CHECK a subgroup of the OAI Incidence cohort was selected which was comparable with the CHECK cohort. Generalized estimating equations (GEE) were used to account for correlations within individuals and all models were adjusted for gender, BMI, age, amount of working hours and baseline radiographic joint damage. Interaction terms were investigated to measure the effect of time and the effect of progression in course of pain and function.

Results:  Data of 688 CHECK participants with knee pain at baseline were analyzed, mean age 56 years, BMI 25 kg/m² and 79% female. The subgroup of OAI Incidence cohort with infrequent or frequent knee pain consisted of 1417 participants, with a mean age of 56, BMI of 28 kg/m²and 64% female. At baseline CHECK had less radiographic OA (K&L ≥ 2) compared to OAI Incidence subgroup, but at follow-up CHECK had more radiographic progression (42% vs 15% of at least 1 K&L point increase; p< 0.001). A final longitudinal regression model with pain as outcome showed slight decrease of course of pain in both cohorts, but a consistent lower level of course of pain in OAI Incidence subgroup of 2 points (better health). In a final model with function as outcome, in both cohorts there is a slight decrease of physical function, but a consistent higher level of function of 10.2 points (worse health) in CHECK. There is no different effect of time in course of pain (p= 0.7) and function (p=0.06) for CHECK or OAI. There is also no different effect of progression of joint damage on course of pain and function (both p=0.07) for CHECK or OAI.

Conclusion: In the total group, participants of the OAI Incidence subgroup and the CHECK participants with knee pain, there is a slight decrease over time in pain and physical functioning. In CHECK participants more progression of joint damage over time was observed and these participants recorded a higher level of pain and function problems. Difference between the 2 cohorts in course of pain and function could not be explained by the effect of time or of progression of joint damage on pain and function.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-between-osteoartritis-initiative-and-check-study-cohort-hip-cohort-knee-development-of-pain-and-function-during-4-years-follow-up/