Bicipital tendinosis is a tendon injury caused by imbalance in movement of the shoulder. In gaming, it is commonly called mouse shoulder due to its prevalence in PC players.
Mouse shoulder is an overuse strain that occurs in the proximal (closer to the center of the body) attachment of the long head of the biceps muscle. The biceps muscle is involved in both elbow and shoulder flexion.
As the name suggests, PC gamers are more likely to experience this injury due to the use of the mouse.
Due to misuse and imbalance, the fiber orientation of the tendon becomes disrupted. This dysfunction is called a tendinosis, which is different than tendinitis—a common misnomer for this condition. We’ll discuss this difference in more detail below.
It’s important to know some basic anatomy of the shoulder to understand mouse shoulder.
To begin, the tendon affected in mouse shoulder is that of the long head of the biceps muscle.
The biceps muscle has two parts (bi- meaning two):
On the distal end (further away from the body), the two parts of the biceps muscle converge and attach to the radius—the bone on the thumb side of your forearm.
This injury is a tendinosis! It is NOT inflammatory in nature, and the term tendonitis is not appropriate! This is critical to determine the appropriate prevention & rehabilitation.
Mouse shoulder occurs when there is at least one of two imbalances in muscle contraction. If one or both of these imbalances occur over time, degeneration of collagen (the protein found in connective tissue) occurs. This leads to the disruption of the tendon fiber orientation in the the biceps tendon.
The strong fibers of a tendon should line up parallel with one another. In tendinosis, these fibers will become jumbled or disorganized—commonly described as adhesion formation—causing pain and affecting the movement of the tendon and the elbow joint.
When concentric contractions occur too frequently without the counterbalance of eccentric contraction, collagen begins to degenerate from the chronic shortening. Eccentric contraction—the lengthening of a muscle & tendon under tension—helps maintain the tendon fiber orientation.
Eccentric contraction protects tendons from overuse injury!
When agonist muscle actions occur too frequently without the counterbalance of their antagonist, there is imbalance in the strength and tension on the joints involved. When strength and tension are not balanced, the muscles can be overworked and injury becomes more common.
If you’re affected by mouse shoulder, you’re likely to experience the following symptoms:
Other common findings may include:
Note: Mouse shoulder is considered an overuse tendinosis, and inflammation will not be present. Inflammation is categorized by pain with accompanying swelling, redness, and heat (feeling warm to the touch).
If you notice these signs of inflammation, you are experiencing something different than simple mouse elbow tendinosis. You should consult your doctor if you are concerned about these symptoms.
For gamers, mouse shoulder is more common for PC users due to lifting the arm or holding the arm up to use the mouse. Common risks for PC users include:
The most common mechanisms of injury for mouse shoulder are imbalances. Therefore, balancing muscle contraction and activation is a simple, yet extremely effective preventative measure.
The lengthening phase of muscle contraction is the most important! For PC gamers, perform resisted flexion exercises and stretches of the shoulder and control the eccentric phase.
It is absolutely essential to perform the eccentric, or “down-phase,” portion of these exercises slowly and under control!
Resisted exercises to add eccentric action to the biceps muscle include:
Supinated front raise
(Incline) biceps curl
Perform this exercise on an incline bench, if possible, to further stretch your biceps tendon. The incline should be approximately 45 to 60 degrees. If you don’t have an incline bench, standing or sitting upright is still useful.
Balancing the muscle activity at any joint will help keep muscles healthy. For PC gamers, flexion of the shoulder is the strenuous action; therefore, it is important to perform extension exercises and stretches for the shoulder.
Shoulder extension exercises and stretches include:
In addition to these mouse shoulder-specific preventative measures, be sure to take breaks to help prevent overuse tendinosis.
To effectively resolve mouse shoulder, it is important to first identify and correct the initial cause. For example, if you’re not performing the eccentric action of the biceps muscle or exercising the shoulder extensor muscles, protocols may be ineffective because of the constant exacerbation.
In practice, rehabilitation protocols for tendinosis injuries are well-researched and highly effective. Treatment is described as a three step process.
The provider should use a firm surface (thumb pressure or a knuckle, for example) to apply moderate pressure to the biceps tendon and scrape perpendicularly across. Unfortunately, this maneuver tends to be moderately painful.
This will loosen the tendon matrix and make it more malleable for the next part of the treatment.
Following cross-friction to loosen the tendon matrix, resistance must be added to lengthen the tendon under tension. This resistance should be moderate-to-significantly heavy in order to properly pull the tendon fibers taut.
For mouse shoulder, the best exercise is an incline dumbbell curl. The provider should place the weight in the patient’s hand with the elbow flexed, and the patient resists the weight downward to pull the tendon.
Using heat packs or other heat therapy (i.e. infrared laser) on the affected area should conclude this protocol. Generally, a heat pack should be used for 10-15 minutes.
Adding a damp towel between the heat pack and the affected area will increase its effectiveness by creating moisture that penetrates further into the body.
Generally, people think to ice their ailments to relieve the pain. However, ice relieves inflammation, and as previously discussed, inflammation is not the cause of pain.
Therefore, ice would not help this condition. In fact, icing the affected area may prolong the healing process.
Heating the area increases blood flow, thereby increasing oxygen and nutrients needed for recovery. For an overuse tendinosis, heat is more helpful than ice.
Following resolution, continuation of these protocols allows for prevention of this condition from reoccurring.
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