Tibiofemoral knee osteoarthritis progresses symmetrically by knee compartment in the GOGO cohort

OBJECTIVE: To evaluate the degree of symmetry of knee osteoarthritis (OA) structural severity and progression of participants with a mean follow-up time of 3.8 years. DESIGN: Participants from the Genetics of Generalized Osteoarthritis (GOGO) study (n ​= ​705) were selected on the basis of radiographic evidence of OA in at least 1 knee, availability of radiographs at baseline and follow-up, and no history of prior knee injury or surgery. Incidence and progression of osteoarthritis were determined by radiographic Kellgren-Lawrence (KL) grade; compartmental OA progression was determined by change in joint space width of lateral and medial tibiofemoral compartments. Total OA progression was the sum of change in KL grade of both knees. RESULTS: Compared with left knees, right knees had more severe KL grades at baseline (p ​= ​0.0002) and follow-up (p ​= ​0.0004), McNemar's χ(2) ​= ​34.16 and 26.08, respectively; however, both knees progressed similarly (p ​= ​0.121, McNemar's χ(2) ​= ​10.09). Compartmental changes were symmetric across knees: medial r ​= ​0.287, p ​= ​0.0002; lateral r ​= ​0.593, p ​= ​0.0002. Change in joint space width in the medial compartment was negatively correlated with change in the lateral compartment of the same knee (left knees: r ​= ​−0.293, p ​= ​0.021; right knees: r ​= ​−0.195, p ​= ​0.0002). CONCLUSIONS: Although right knees tended to have more severe OA at both baseline and follow-up, radiographic progression did not differ by knee and compartmental progression correlated across knees. Given this trend in generalized OA, the risk of progression for both knees should be considered, even if only one knee has radiographic OA at baseline.