Consequences of imbalanced joint-muscle loading of the femur and tibia: from bone cracking to bone loss

Bone is a living tissue requiring regular mechanical stress stimulation to maintain its mass and organization, but excessive stresses may damage its structural integrity. Stresses and strains that are above or below critical levels may cause acute or accumulated bone damage. Such stresses and strains are frequently the result of imbalanced joint-muscle forces. In this study, three-dimensional (3D) anatomically accurate models of the femur and tibia were utilized to determine alterations in bone stresses during two situations of imbalanced joint-muscle loading, muscular weakness during intensive physical exercise, and exposure to micro-gravity during a space flight. Substantial alterations in stress levels were observed in both conditions. For the first case, it was concluded that normal function of the soleus muscle is essential for reducing bending-related tension on the tibial cortex. For the second case, it was concluded that trabecular bone within the femoral neck is found under more profound stress deprivation than cortical bone when exposed to micro-gravity.