"Trendelenburg sign" is positive in damage of the following nerve :

C i.e. Superior gluteal nerve In paralysis of gluteus medius & minimus (i.e. injury to superior gluteal nerve) trendelenburg sign is positive not in paralysis of gluteus maximus (i.e. inferior gluteal nerve injury)Q Trendelenburg Sign Normally when the body weight is suppoed on one limb, the glutei (medius & minimus) of the suppoed side contract & raise the opposite & unsuppoed side of pelvis. If the abductor mechanism is defective the unsuppoed side of pelvis dropps & this is known as positive trendelenburg's test. Tredelenburg's test. (A) When both feet are suppoing the body weight, the pelvis (anterior superior iliac spine) on the two sides lies in the same horizontal plane. (B) When only the right foot is suppoing the body weight, the unsuppoed side of the pelvis is normally raised by the opposite gluteal medius and minimus. (C) If the right gluteal medius and minimus are paralysed, the unsuppoed left side of the pelvis drops. This is a positive Tredenburg's test. When the patient walks with positive trendelenburg sign, the pelvis descends on the unsuppoed side, the lower limb becomes, in effect, too long and does not clear the ground when the foot is brought forward. To compensate, the individual leans away from the unsuppoed side (i.e. towards affected side), raising the pelvis to allow adequate room for the foot to come forward.