231 SYMMETRY OF RADIOGRAPHIC KNEE OSTEOARTHRITIS PROGRESSION IN SIBLING PAIRS WITH HAND OSTEOARTHRITIS

231 – Table 1. Symmetry of knee OA progression MJS Right Knee MJS Right Knee MJS Left Knee MJS Left Knee Medial Compartment Lateral Compartment Medial Compartment Lateral Compartment Ipsilateral-medial -0.226 (812)* -0.2137 (829)* Ipsilateral-lateral -0.226 (812)* -0.2137 (829)* Contralateral-medial 0.4609 (1117)* -0.0822 (774) 0.4609 (1117)* -0.0257 (788) Contralateral-lateral -0.0257 (788) 0.4462 (721)* -0.0822 (774) 0.4462 (721)* Sum KLG -0.2388 (1174)* -0.00007(819) -0.1596 (1129)* -0.0054 (796) Sum Osteophytes -0.0768 (1172) 0.0241 (815) -0.1483 (1179)* -0.0585 (834) Sum JSN -0.3787 (1164)* -0.0488 (812) -0.4009 (1168)* -0.1094 (832) Values are Pearson R coefficients (N individuals with data available for analysis of a particular set of variables) *p<0.0001. the same or within 1 grade of each other in the majority of participants (89%). With regard to knee OA progression, significant correlations were observed in a symmetic pattern across compartments of the knee (Table 1). Namely, medial compartment progression in one knee was strongly associated with medial compartment progression in the contralateral knee. Likewise, lateral compartment progression in one knee was strongly associated with lateral compartment progression in the contralateral knee. Conclusions: Although we hypothesized that knee OA progression in one knee would increase the likelihood of progression in the contralateral knee, we were surprised to observe remarkable compartmental symmetry of knee OA progression. This was particularly intriguing given the method of recruitment that required hand but not knee OA. These data show that knee OA is both frequent, and progression compartmentally symmetric in siblings from families with hand OA, favouring strong genetic/constitutional risk for progression.