2005 OITE Question 76

Question

Compared to a normal hip, the hip joint forces during the stance phase of gait in a patient with a Trendelenburg lurch are

1- increased.

2- decreased.

3- unchanged.

4- dependent on the alignment of the contralateral hip.

5- dependent on the alignment of the contralateral knee.

Figures

Answer (click for answer)

PREFERRED RESPONSE: 2

For this question you need to know what causes a Trendelenburg lurch and the biomechanical explanation of why it occurs. First, a Trendelenburg lurch is a limp caused by weakness in the abductors of the hip (gluteus medius/minimus). By definition, it is a result of decreased forces across the hip joint and occurs irrespective of the function of the contralateral lower extremity. The answer has to be #1. Second, to understand why a Trendelenburg lurch occurs, you need to understand the forces across the joint. Visualize contraction of the gluteus medius and minimus as both pulling the femur into abduction and erecting the trunk. During stance phase, the foot is planted on the ground, but the weak abductors are unable to keep the trunk erect, i.e., the body leans away from the affected hip, and the unaffected hip appears to sag. In compensation, the upper body leans back over the affected side to maintain balance. This posturing is repeated every stance phase of ambulating and gives the appearance of a lurch.

Reference: RECOMMENDED READINGS: Hurwitz DE, Andriacchi TP: Biomechanics of the hip, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip. Philadelphia, PA, Lippincott-Raven, 1998, pp 75-85.