Heat-Induced Limb Length Asymmetry Has Functional Impact on Weight Bearing in Mouse Hindlimbs

Limb length inequality results from many types of musculoskeletal disorders. Asymmetric weight bearing from a limb length discrepancy of less than 2% can have debilitating consequences such as back problems and early-onset osteoarthritis. Existing treatments include invasive surgeries and/or drug regimens that are often only partially effective. As a noninvasive alternative, we previously developed a once daily limb-heating model using targeted heat on one side of the body for 2 weeks to unilaterally increase bone length by up to 1.5% in growing mice. In this study, we applied heat for 1 week to determine whether these small differences in limb length are functionally significant, assessed by changes in hindlimb weight bearing. We tested the hypothesis that heat-induced limb length asymmetry has a functional impact on weight bearing in mouse hindlimbs. Female 3-week-old C57BL/6 mice ( = 12 total) were treated with targeted intermittent heat for 7 days (40 C for 40 min/day). High-resolution x-ray ( = 6) and hindlimb weight bearing data ( = 8) were acquired at the start and end of the experiments. There were no significant left-right differences in starting tibial length or hindlimb weight bearing. After 1-week heat exposure, tibiae ( = 7.7,