Background Osteoarthritis (OA) can be manifested in structural changes occurring at the joint level, like joint space narrowing (JSN) and osteophyte formation. Preliminary findings of the Osteoarthritis Initiative after 10 years suggest possibly different mechanisms in structural changes for JSN and osteophyte formation.1 It is proposed that formation of osteophytes should be considered as an early feature of OA.2
Objectives This study focuses on the heterogenic expression of osteophyte formation and aims to identify subgroups of participants with homogeneous patterns of osteophyte formation over time (trajectories), and to describe the prognostic factors of the different subgroups.
Methods Longitudinal data of quantitative osteophyte formation, calculated as total area of mm2, over a period of five years follow-up of the early OA cohort CHECK (Cohort Hip and Cohort Knee) was used. Latent Class Growth Analysis identified homogenous subgroups with distinct trajectories of osteophyte formation. Multinomial regression analysis was used to examine the prognostic factors of the different subgroups.
Results In data of 5 years follow-up of 929 participants, three subgroups were identified: an “osteophyte increase” subgroup (n=32) with an increase in osteophyte formation, “mild osteophyte” subgroup (n=181) with minimal increase, and “no osteophyte” subgroup (n=716) without increase in osteophyte formation. Being older, a BMI above 25, the existence of local clinical signs at baseline (crepitus, warmth, bony tenderness, enlargement and effusion), and radiographic characteristics (initial osteophyte formation, narrowing of JSW) suggested a higher probability of a (mild) increase in osteophyte formation.
Conclusions In participants with early symptomatic OA the common course of osteophyte formation over a period of 5 years is relatively flat. However, in a small subpopulation there was a remarkable increase in osteophyte formation. Identifying which patients will develop structural changes may in the future lead to specific treatment of these patients.
Eckstein F, Kwoh CK, Link TM. Imaging research results from the Osteoarthritis Initiative (OAI): a review and lessons learned 10 years after start of enrolment. Ann Rheum Dis 2014;73:1289-300
Hart DJ, Spector TD. Kellgren & Lawrence grade 1 osteophytes in the knee – doubtful or definite? Osteoarthritis Cartilage 2003;11:149-50.
Acknowledgements CHECK-cohort study is initiated by the Dutch Arthritis Foundation and performed within; Erasmus Medical Center Rotterdam; Kennemer Gasthuis Haarlem; Leiden University Medical Center; Maastricht University Medical Center; Martini Hospital Groningen /Allied Health Care Center for Rheum. and Rehabilitation Groningen; Medical Spectrum Twente Enschede /Ziekenhuisgroep Twente Almelo; Reade, formerly Jan van Breemen Institute/ VU Medical Center Amsterdam; St.Maartens-kliniek Nijmegen; University Medical Center Utrecht and Wilhelmina Hospital Assen.
Disclosure of Interest None declared