Leg length inequality is a relatively common musculoskeletal malalignment related to structural, postural and environmental factors. The inequality is a plausible aetiological factor in the development of a variety of overuse injuries because it alters the magnitude and distribution of mechanical stress within the body. Leg length inequality has been linked with lower extremity stress fractures, low back pain, hip pain and vertebral disk problems of runners. The appropriateness of using inshoe lifts to reduce or eliminate the inequality has not been rigorously evaluated. Further research is needed to quantify the biomechanical effects of leg length inequality as it interacts with other factors related to running injury.