28/02/2026
https://www.facebook.com/share/p/1AxeWVckJt/
CENTRE OF GRAVITY SHIFT & BIOMECHANICAL ALIGNMENT
In ideal standing and single-leg support, the body’s centre of gravity (COG) is carefully aligned so that the line of gravity passes through the trunk, pelvis, hip, knee, and finally the foot. This vertical alignment minimizes muscular effort while maximizing joint stability. When alignment is optimal, ground reaction forces are efficiently transferred upward, allowing the skeleton to bear load with minimal strain on soft tissues.
In normal single-leg stance, the COG shifts slightly toward the stance limb, but it remains well controlled. The pelvis stays level because the hip abductors (especially gluteus medius and minimus) generate sufficient force to counterbalance body weight. This creates a stable pelvis, keeps the lumbar spine relatively neutral, and allows the knee and ankle to remain stacked under the trunk. The result is efficient load sharing, reduced joint stress, and economical movement.
In contrast, during a Trendelenburg alignment, weakness or delayed activation of the stance-side hip abductors alters this balance. As body weight loads the stance limb, the pelvis drops on the unsupported side. To prevent falling, the trunk often leans toward the stance side, shifting the COG laterally. Although this compensatory lean reduces the hip abductor demand, it disrupts overall biomechanical alignment and increases compressive forces across the hip joint.
This altered COG shift has consequences throughout the kinetic chain. At the hip, joint reaction forces rise and local stabilizers are overworked. At the lumbar spine, lateral flexion and asymmetrical loading increase shear stress, often contributing to low-back discomfort. Distally, the knee may experience altered valgus or varus moments, while the ankle and foot adapt through pronation or supination to maintain balance.
Over time, repeated movement with poor COG control leads to inefficient gait patterns, early fatigue, and a higher risk of overuse injuries. What begins as a local hip control issue can manifest as knee pain, lumbar strain, or foot and ankle dysfunction. This highlights why alignment is not just a static concept but a dynamic interaction between muscle control, joint positioning, and gravity.
From a biomechanical perspective, restoring proper alignment means improving hip abductor strength, neuromuscular timing, and trunk control. When the pelvis is stabilized and the COG remains closer to the base of support, the entire body moves more efficiently. Balanced alignment reduces compensations, protects joints, and supports pain-free movement during standing, walking, and functional activities.
In summary, the image illustrates a powerful principle: where the centre of gravity goes, alignment follows. Maintaining controlled COG positioning is fundamental to healthy biomechanics, efficient load transfer, and long-term musculoskeletal resilience.