Familial, structural, and environmental correlates of MRI-defined bone marrow lesions: a sibpair study

The aim of this study was to estimate the heritability and describe the correlates of bone marrow lesions in knee subchondral bone. A sibpair design was used. T2- and T1-weighted MRI scans were performed on the right knee to assess bone marrow lesions at lateral tibia and femora and medial tibia and femora, as well as chondral defects. A radiograph was taken on the same knee and scored for individual features of osteoarthritis ( radiographic osteoarthritis; ROA) and alignment. Other variables measured included height, weight, knee pain, and lower-limb muscle strength. Heritability was estimated with the program SOLAR ( Sequential Oligogenetic Linkage Analysis Routines). A total of 115 siblings ( 60 females and 55 males) from 48 families, representing 95 sib pairs, took part. The adjusted heritability estimates were 53 +/- 28% ( mean +/- SEM; p = 0.03) and 65 +/- 32% ( p = 0.03) for severity of bone marrow lesions at lateral and medial compartments, respectively. The estimates were reduced by 8 to 9% after adjustment for chondral defects and ROA ( but not alignment). The adjusted heritability estimate was 99% for prevalent bone marrow lesions at both lateral and medial compartments. Both lateral and medial bone marrow lesions were significantly correlated with age, chondral defects, and ROA of the knee ( all p < 0.05). Medial bone marrow lesions were also more common in males and were correlated with body mass index (BMI). Thus, bone marrow lesions have a significant genetic component. They commonly coexist with chondral defects and ROA but only share common genetic mechanisms to a limited degree. They are also more common with increasing age, male sex, and increasing BMI.