Peripheral whole blood samples from subjects affected by OA and implanted with THA were harvested and genotyped by MacInnes et al. Half of the patients with osteolysis had eight single nucleotide polymorphisms associated with susceptibility to osteolysis: four of these lie within bone resorption (RANK), and the other four within Kringle containing transmembrane protein 2 (KREMEN2), OPG, Secreted frizzled related protein 1 (SFRP1) and the regulator of inflammatory signaling (TIR domain containing adaptor protein (TIRAP)), respectively. Here, SFRP1 is linked to primary osteolysis.