Skeletal asymmetry -vs- muscular asymmetry
Last time we got to grips with the idea that horses are naturally asymmetrical, albeit very subtle in non-deformed horses – and that is just the very tip of a very large iceberg. This month we tackle skeletal and muscular asymmetry and recognise that there is a big difference!
You may first notice that there is a difference if the horse is not pushing evenly through from behind, if they are stiff on one rein or if they tend to ‘load’ one shoulder more than the other, for example. You may even notice it when you stand them square and assess them. Skeletal and muscular asymmetry, especially on structures such as the pelvis, can be hard to distinguish.
This black mare is a companion and she exhibits skeletal asymmetry. She came to me after she got cast in the stable and showed a marked pelvic asymmetry, to a degree that would suggest an influence other than naturally occurring asymmetry. Compare the height of both ‘points of hip’ (tuber coxae) and you can see the left is lower. The second picture was taken immediately following treatment and you can see the asymmetry is significantly improved, i.e. the ‘points of hip’ are a lot more level and the muscle mass is too (consider the tail is blowing to the left).
The chestnut mare is a dressage horse and she exhibits muscular asymmetry. She came to me with difficulty in canter, which has resolved, and now has regular treatments to maintain her correctness. This picture was taken immediately after treatment when the pelvis was level, and if you look closely, you can see the difference in muscle mass. Her left hindquarter is less developed than her right. She works hard at strengthening the left hindquarter so she is more balanced throughout her body and it is improving now that there is no pain in the pelvis.
The relationship between skeletal and muscular asymmetry is strong. I commonly find that horses with skeletal asymmetry may not have a marked muscular asymmetry; although if the issue has been long-term or chronic then muscular asymmetry is often present too due to compensation mechanisms. On the other hand, muscular asymmetry has a profound effect on the skeleton. Stronger muscles have a greater ‘pull’ on the bones and can influence skeletal asymmetry over time. This is why it is so important to consider WHY the body is asymmetrical, WHAT you can do to rebalance it, and HOW you will achieve it.
Often manipulative therapists will rebalance the bones and then provide you with a tailored strengthening programme with certain exercises and stretches to help the muscles adapt and remain more symmetrical. Sometimes there is not enough time in the day to stick to the programme, which is where an in-patient rehabilitation service by a therapist will be most useful. They can treat the horse and take him/her through the programme under careful watch to make sure he/she has the best chance. This is incredibly important to prevent injury, behavioural issues, etc., and of course to improve comfort and performance.