Ground reaction forces. Rats with medial meniscus transection (MMT) surgery had significantly different vertical force-time curves in their operated limb relative to their contralateral limb, as indicated by lower peak vertical force (top left, operated limb, open box; contralateral limb, open circle; P = 0.016) and vertical impulse (bottom left; operated limb, open box; contralateral limb, open circle; P = 0.003). Peak vertical force also varied between animals with MMT surgery and naive controls (solid box, P = 0.004), but not between animals with MMT surgery and MCL sham animals (shaded box, top middle). Vertical impulse, however, was lower in animals with MMT surgery relative to both naïve controls (P < 0.001) and medial collateral ligament (MCL) sham animals (P = 0.019, bottom middle). Like vertical force-time curves, braking-propulsion curves also varied between surgical groups, although changes were restricted to the propulsive phase of the curve. Peak propulsive forces were significantly lower in animals with MMT surgery relative to naïve controls (P = 0.003) and tended to be lower than those of MCL sham animals (P = 0.053, top right). Propulsive impulse was also significantly lower in animals with MMT surgery relative to naïve control (P < 0.001) and tended to be lower than MCL sham animals (P = 0.081, bottom right). Finally, MCL sham animals also tended to have a lower propulsive impulse than naïve controls (P = 0.079). Data are presented as mean ± standard deviation. *Differences between surgical groups that are significant at a level of P < 0.05; ^differences near significance at a level of 0.1 <P ≤ 0.05.