Biomechanics of the Hip & Effect of a Walking Stick
DNB Orthopaedics • October 2024 • Paper I • 10 Marks
Introduction
The hip is a ball-and-socket, weight-bearing joint designed to combine stability with a large range of motion. During standing and walking, forces acting across the hip are considerably greater than body weight because body weight produces an adduction moment that must be counterbalanced by the hip abductor muscles.
Central biomechanical principle
During single-leg stance, body weight tends to tilt the pelvis toward the unsupported side. The abductors of the stance hip generate an opposing moment to maintain a level pelvis.
Forces Acting Across the Hip
The major forces are:
- Body weight (BW)
- Hip abductor muscle force (M)
- Joint reaction force (JRF)
The principal abductors maintaining pelvic stability are:
- Gluteus medius — most important
- Gluteus minimus
- Tensor fasciae latae
1. Double-Leg Stance
When standing symmetrically on both lower limbs, the body's centre of gravity lies approximately in the midline. Body weight is distributed between the two hips.
BODY WEIGHT
↓
│
│
[ PELVIS ]
/ \
O O
Left hip Right hip
↑ ↑
Reaction Reaction
The abductor demand is relatively low compared with single-leg stance because…