Suspension effects on rat femur-medial collateral ligament-tibia unit

To study the influence of a 2-wk absence of normal weight-bearing forces on dense fibrous connective tissues of growing animals, the geometrical and biomechanical characteristics were examined of femur-medial collateral ligament (MCL)-tibia units (FMT unit) of age-matched controls and tail-suspended young male rats. During the 2-wk suspension, the rate of longitudinal growth of MCL decreased significantly, but no differences were found in the cross-sectional area of the MCL of the two groups. The tensile stiffness of suspension FMT units was significantly less than control, and the proportional, maximum, and failure loads of FMT units were also significantly less for the suspended animals. The stresses in the suspension MCL at the proportional limit were significantly less than control values. These results indicated that a 2-wk absence of normal weight-bearing forces adversely affected the rate of longitudinal growth of MCL and the mechanical properties of the rat FMT unit.