A 29 years old female presents to you with difficulty in walking and climbing stairs for the last 3 weeks. Physical examination reveals a waddling gait, with her trunk swaying from side to side towards the weight bearing limb. When she stands on her right leg, the pelvis on the left side falls; but when she stands on the left leg, the pelvis on the right side rises. Which of the following nerves is injured?

Answer: (d) Right superior gluteal nerve.Injury to Superior Gluteal Nerve* Injury to this nerve results in a characteristic motor loss, resulting in a disabling gluteus medius limp, to compensate for weakened abduction of the thigh by the gluteus medius and minimus, and/or a gluteal gait, a compensatory list of the body to the weakened gluteal side.* This compensation places the center of gravity over the supporting lower limb. Medial rotation of the thigh is also severely impaired.* When a standing person is asked to lift one foot off the ground and stand on one foot, the gluteus medius and minimus normally contract as soon as the contralateral foot leaves the floor, preventing tipping of the pelvis to the unsupported side.* When the pelvis descends on the unsupported side, the lower limb becomes, in effect, too long and does not clear the ground when the foot is brought forward in the swing phase of walking.* To compensate, the individual leans away from the unsupported side, raising the pelvis to allow adequate room for the foot to clear the ground as it swings forward.* This results in a characteristic "waddling" or gluteal gait.* When a person who has suffered a lesion of superior gluteal nerve is asked to stand on one leg, the pelvis on the unsupported side descends, indicating that the gluteus medius & minimus on the supported side are weak or non-functional - positive Trendelenburg test* Other causes of this sign include fracture of the greater trochanter (the distal attachment of gluteus medius) and dislocation of the hip joint.* The patient's pelvis falls on the "left" side, therefore the "right" superior gluteal nerve is injured.* The Trendelenburg's test is positive when the patient stands on one leg and the pelvis on the opposite side falls due to the paralysis of hip abductors. Normally, the opposite side rises to maintain the center of gravity.