Have you ever wondered why certain yoga asanas can feel so easeful in your body while other asana can feel like such a challenge? Or why one person can sit cross-legged for hours having never practised yoga before and you still need to sit on four cushions after having practised yoga for years? The short answer to this is that every body is entirely unique, with a unique range of movement in each joint and therefore we will each express a certain yoga pose in a completely unique way. Let’s explore this further by looking at our hip joints in more detail.

The bony components of the hip joint are the head of the femur and the acetabulum of the hip bone, also known as the hip socket. The femur is the longest and strongest bone in the human body. The proximal end of the femur consists of the head, neck and shaft. The greater trochanter and lesser trochanter are bony landmarks on the femur that serve as attachment points to many of the key muscles of the hip.

Femoral neck-shaft angles (in blue in the image above) show considerable variation within human populations. There are no universally accepted normal or abnormal angles. Anderson and Trinkaus (1998) stated that mean values range from 122° to 136°, and normal individuals are found from around 110° to almost 150°. Relating this natural variation to yoga, the femoral neck-shaft angle will impact the degree to which one can move one’s leg directly out to the side (abduction) in a pose like Wide Leg Forward Fold (Prasarita Padottanasana). 

The femoral neck in the average person is also rotated slightly anteriorly and this is referred to as femoral anteversion (AV). Bråten et al (1992) found significant variation amongst the group in their study and stated that the mean AV angle was 18° in the women and 14° in the men. The mean left/right difference in AV was 3.8°. The AV angle will inevitably impact the range of movement of the hip joint in flexion, extension and rotation. 

The image below on the left, courtesy of Paul Grilley, beautifully demonstrates this huge variation in the position of the head of the femur relative to the shaft of the femur between individuals. The femur on the left might make it reasonably easy for that student to sit in Lotus Pose while the femur on the right might make it really difficult for that student to even sit crossed-legged. Lotus Pose might be physically impossible for that student no matter how much they practise. As mentioned above, for the same individual there can be a huge difference in the architecture of their right and left femur.

The bony structure of the acetabulum (hip socket) also varies immensely from person to person. While one yoga student may have a shallow acetabulum, another student may have a much deeper one. This variation can impact the range of movement of the hip joint in all directions. The actual position of the acetabulum on the hip bone also varies immensely. Some people have an acetabulum that is positioned slightly further forward on the hip bone or further back, angled upward or downward. There are an infinite number of possibilities here.

The image above on the right is another beautiful demonstration of how the position, shape and size of the acetabulum can vary immensely. It’s also important to note that no pelvis is perfectly symmetrical in any plane and therefore there can also be immense variation between the architecture of the right acetabulum and the architecture of the left acetabulum in the same person.

Finally, our bodies are not naturally symmetrical. No one has a right hip joint that is architecturally identical to their left hip joint. This means that your right hip joint will always have a different range of movement compared to the left. While practising Extended Triangle Pose (Trikonasana) easily on the right we might find that there is a sense of compression in the left hip that requires us to step our feet closer together to overcome.

Sitting in Lotus Pose is not physically attainable for most of the population simply because of the bony architecture of our pelvises and femurs. Yoga is a wonderful practice for developing a deep sense of awareness of our bodies and is a powerful way to move towards accepting our limitations and celebrating our uniqueness.

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References:

Anderson, J. and Trinkaus, E. (1998) ‘Patterns of sexual, bilateral and interpopulational variation in human femoral neck-shaft angles.’ J. Anat 192, 279–285.

Bråten, M., Terjesen, T. and Rossvoll, I. (1992) ‘Femoral anteversion in normal adults.’ Acta Orthopaedica Scandinavica 63, 1, 29-32.