Tactile allodynia. Rats with medial meniscus transection (MMT) surgery had lower right (operated) paw withdrawal thresholds (open box) than their contralateral limb (open triangle; P = 0.017, middle) and tended to have lower right (operated) paw withdrawal thresholds than naïve controls (solid triangle, P = 0.056, right), but not medial collateral ligament (MCL) sham animals (shaded triangle). Rats with MCL sham surgery also tended to have differences between the operated limb (shaded triangle) and the contralateral limb (shaded box, P = 0.065, left). Data are presented as mean ± SEM. *Differences between surgical groups at a level of P < 0.05; ^differences near significance at a level of 0.1 <P ≤ 0.05.