Some people walk into their first yoga class, press the soles of their feet together and boom – their knees fall right to the ground for a perfect bound angle pose. Other people practice for decades and still need to sit on something to get their knees to level with their hip bones – the measure for this pose to be safe for your spine. Often, the latter group will ask their teacher “will my hips ever open?”. The answer is, most likely, no. That doesn’t mean you should stop stretching them – but it might change how and why you stretch them.
If your hip mobility is limited when you first begin yoga, there is hope of improvement. However, if you’ve been working on it for years or even decades, the problem is most likely the structure of the joint itself. Just as human beings come in a variety of shapes and sizes, so do their bones. The largely ignored consequence of this diversity is that human movement varies greatly from person to person. Your ability to perform many traditional yoga poses is determined more by the shape of your bones than the stretch of your muscles.
While there is infinite variety in the human form, there are two main structural differences in the hip joint that inform your ability to perform yoga poses. The first is the size of your femur head & the depth of your acetabulum (hip socket). People with a deeper hip socket tend to have less mobility in their hips because the bones with encounter limitations more quickly. In the photograph below you can see eight variations on the shape and size of the human femur head.
The second common structural difference that may affect your ‘flexibility’ is the angle of your femoral neck angle. The part of your thigh bone that sits in the acetabulum is normally angled from the rest of the bone at around 126°. In some humans the angle is larger (called coxa valga). This leads to bowleggedness and a potentially greater range of motion in some yoga poses. In others, when the angle is smaller (coxa vara) it is associated with knock knees and a diminished range of motion. You can see the comparison in the image below and imagine the very difference ranges of motion available to these people.
Knowing this, the final form of a yoga pose no longer seems like a useful goal for many of us. So then, why keep stretching your hip muscles in yoga class? Check back next week for a blog post detailing the why & how of caring for your hip joint.