August's muscle is the Supraspinatus, a muscle in the shoulder group which can be prone to injury in active dogs. Read on to find out more about the anatomy, function, injury risk, and treatment options if needed.
The Anatomy
The Supraspinatus is located in the forelimb of the dog on the upper arm, and cranial (closer to the head) part of the shoulder. It is a spindle shaped muscle, that is round and thick, with a fusiform structure, meaning all the muscle spindles in the belly of the muscle run parallel to each other.
The muscle's origin is on the supraspinous fossa, which is the area at the top of the shoulder blade, and also down the scapula spine, which is a thin bony spine that runs down the centre of the shoulder blade. The muscle then moves down the forearm, crosses the shoulder joint, and inserts on the greater tubercle of the humerus, which is a prominent bony feature that can be felt on the front of the chest area.
What does it do?
Now you know that the Supraspinatus is located at the shoulder joint, but what does it do?
The canine shoulder joint is able to move in all directions, but the primary function in movement is flexion and extension. Stability and movement of the shoulder relies on a group of muscles, which includes the Supraspinatus, making up the rotator cuff. The rotator cuff, as in humans, is a group of muscles and tendons that surround the shoulder, keeping the joint stable and in place.
Due to the position of the Supraspinatus on the front of the shoulder blade, its primary function is to extend the shoulder, bringing the forelimb forward. It also works as a shoulder stabiliser as part of the rotator cuff. Whenever your dog is reaching forward with their forelimb, when walking, trotting, or running, the muscle is at work.
Can the Supraspinatus become injured?
As with any muscle, the Supraspinatus can be injured - strained, weak, overused. The most recognised condition that affects the muscle is Supraspinatus Tendinopathy (disease of the tendon) which is similar to rotator cuff injury in humans. This problem is defined by injury to the tendon of the Supraspinatus muscle, the tendon is the connective tissue that joins the muscle to the bone at the point of insertion.
This condition is a common cause of forelimb lameness in performance, working and active pets. The injury is normally caused by chronic repetitive activity, for example, landing a jump with the forelimbs outstretched, or fast turns, which put the soft tissue structures under stress. These types of movement are commonly performed by canine athletes, working dogs, and pets. As repeated force is put on the tendon, the fibres are disrupted causing inflammation and pain. If untreated, scar tissue can build up in the area, causing more discomfort, and in chronic cases the bone can remodel.
The signs you may see in a case of Supraspinatus Tendinopathy are; fore limb lameness, shortened stride/step on the affected limb, changes in performance such as unwillingness to jump down. Lameness may get worse after exercise or heavy activity.
Treatment
Following cases of Supraspinatus Tendinopathy, rehabilitation is important to help return to full function. The process would focus on muscle strengthening and reconditioning to protect from re-injury. I would also perform exercises to maintain joint health and increase the range of motion of the shoulder joint.
As with any other muscular injury, I use massage therapy and stretching to address tense areas of muscle, and I prescribe exercises to build muscle, allowing it to function optimally.
For more information about what I do and how I could help your animal please get in touch. See you next month for September's 'Muscle of the Month'.
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