The shoulder joint is the only one in the horse’s body that does not have ligaments to hold it in place. Instead, the joint is surrounded by muscles that hold it together and facilitate movement. There are three main muscles: subscapularis,supraspinatus, and infraspinatus. The first one is underneath the scapula, so not one I work on. The other two, the spinatus muscles, are very important for lateral work, and muscles I work on a lot. If your horse is displaying a shortened stride in front, or head bobbing lameness, there may be pain in one of the spinatus muscles. If your horse gets cast, the spinatus muscles often bear the brunt of the trauma, as the spinatus muscles are what prevent the shoulder from being dislocated.
Yesterday I worked on a lovely Holsteiner mare that I was told had atrophy (also referred to as Sweeney) of the shoulder muscles. I found two big spasms high up on the spinatus muscles and worked to release them. I will return to see how the muscles respond. Often, once the spasms are released, circulation flows freely and the muscle can regain health. This case might also benefit from cold laser therapy.