‘Bend the knees’ is often spoken like a mantra when associated with lifting activities, and is thought to prevent excess loading of the spine.
In fact the directive should be more accurately described as bend the hips.
Bending the knees without bending the hips will encourage a tucked under tail and flat lower back. This posture in fact places the spine into its weakest, most unstable position. Therefore it will be vulnerable even before the lifting activity.
So what do we mean when we say ‘bend the hips’? In fact where exactly are the hip joints?
The hip joints are ball and socket joints at the level of the groins, in the front, and the sitting bones, at the back. They are the joints between the thigh bones and sides of the pelvis, which is bowl shaped. The sitting bones are 2 rocker shaped bones at the base of the pelvic bowl. So you are able to bend your hips either by tilting the pelvic bowl forwards on the thigh bones ie sitting bones move back and widen; or by moving the thigh bones forward on the pelvic bowl ie lifting the leg.
Let’s go back to our lifting position. Yes a slight bend of the knees is helpful to unlock the hamstrings but then the emphasis should be to bend the hips. Via a gentle press of the feet, to meet the ground; the sitting bones are widened from each other as they are reached back and up. If the load to be lifted is lower, the sit bones need to move further back up and apart (picture 3). This has been deliberately exaggerated to help clarify the correct action.
Thus the pelvis rocks forward on the thigh bones, the lower back maintains its natural curve and unhealthy loading of the spine is minimised.