mouse elbow anatomy

Mouse elbow: a devastating injury for PC gamers

Lateral epicondylosis is a tendon injury more commonly known as “tennis elbow.” However, in gaming, it is commonly called mouse elbow due to its prevalence in PC players.

What is mouse elbow?

Mouse elbow is an overuse strain that occurs in the extensor tendons of the wrist and fingers that attach to the outside (thumb side) of the elbow. The muscles involved are the extensor muscles that open the hand and bend back the wrist.

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 extensor tendons on the outside of the elbow become 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.

Pertinent anatomy

It’s important to know some basic anatomy of the wrist and elbow to understand mouse elbow.

To begin, the tendons affected in mouse elbow are collectively called the common extensor tendon. This tendon is made up of 4 individual muscles that converge in one spot—a projection on the outside of the humerus (arm bone) called the lateral epicondyle:

  • Extensor carpi radialis brevis: extension and radial deviation of your wrist
  • Extensor digitorum: extension of your wrist and 4 fingers
  • Extensor digiti minimi: extension of your wrist and pinky finger
  • Extensor carpi ulnaris: extension and ulnar deviation of your wrist

One additional muscle which may be involved attaches just above the common extensor tendon onto the supracondylar ridge of the humerus.

  • Extensor carpi radialis longus: extension and radial deviation of your wrist
the muscles that make up the common extensor tendon
These muscles make up the common extensor tendon

On their distal ends (further away from the body), each of these muscles attach to different parts of the hands or fingers, but the tendinosis occurs in the attachment at the elbow.

Pathophysiology

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 elbow 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 common extensor 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.

Mouse elbow in gamers
The fibers of the common extensor tendon become jumbled or disorganized
  • Concentric vs. eccentric imbalance
    • Concentric: the shortening phase of a muscle contraction
      • PC gamers: lifting the fingers off the mouse is a concentric contraction; lifting the fingers requires more force than striking the keys or mouse buttons
      • Weight lifting example: the up-phase of a biceps curl (raising the dumbbell up to your shoulder)
    • Eccentric: the lengthening phase of a muscle contraction
      • In gaming, there is no instance of an eccentric contraction, and this is the problem!
      • Weight lifting example: the down-phase of a biceps curl (controlled lowering of a dumbbell back to your hip)
  • Agonist vs. antagonist imbalance
    • Agonist: the active muscle during a particular movement
      • PC gamers: the agonist tends to be the extensor muscles; lifting the fingers off the keyboard & mouse is a resisted movement (against gravity), where tapping keys & mouse buttons requires little muscle activation
    • Antagonist: the muscle that opposes the agonist; this muscle (or group of muscles) will be relaxed during agonist contraction
      • PC gamers: the antagonist muscles are the flexor muscles of the wrist and hand (i.e., making a fist); these muscles are not challenged with any significant resistance during PC gaming
eccentric contraction
A sample of eccentric contraction of the biceps muscle, lowering the arm

For console gamers, these imbalances are not pertinent for mouse elbow. These imbalances in console gaming are more likely to lead to medial epicondylosis or trigger finger.

Concentric vs. eccentric imbalance

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!

Agonist vs. antagonist imbalance

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.

Signs & symptoms

If you’re affected by mouse elbow, you’re likely to experience the following symptoms:

  • Pain
    • Most often, you will experience pain at the outer portion of your elbow with wrist movements and gripping
    • Bending your wrist and fingers back will cause pain by contracting the extensor muscles
    • Flexing your wrist and fingers forward will cause pain by stretching the extensor muscles
  • Weakness
    • Gripping may feel weak; however, your perceived weakness is more likely due to pain rather than true muscle weakness
outer elbow pain
The most common symptom of mouse elbow is pain on the outer portion

Other common findings may include:

  • More pronounced symptoms with extension of your wrist(s) (i.e., using a mouse or keyboard)
  • Worsening symptoms following periods of rest
  • Relief or improvement of symptoms after warming up the extensor muscles

Note: Mouse elbow 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.

Common mechanism(s) of injury

For gamers, mouse elbow is more common for PC users due to the position and action of the hands using a keyboard & mouse. Common risks for PC users include:

  • Poor hand position
    • Allowing excessive extension of your wrists over the keyboard and/or mouse will create over-activation and shortening of the common extensor muscles & tendons
    • Allowing excessive ulnar deviation (bending of your wrist towards the pinky side) may lead to aggravation of the extensor carpi ulnaris, specifically
  • Lack of eccentric contraction
    • As described in Pathophysiology above, the actions performed in PC gaming do not include eccentric contraction, or lengthening of the extensor muscles
    • The imbalance of muscle shortening without lengthening under tension leads to tendon fiber disruption
  • Lack of antagonist muscle contraction
    • Also described in Pathophysiology above, lifting your fingers off the keyboard & mouse is a more aggressive activity; pressing keys & mouse buttons down is not a strong muscle activity
    • The lack of forceful flexor muscle contraction allows for over-activity of the extensor muscles, perpetuating the shortening and fiber disruption of the tendons at the elbow
keyboard hand position
Poor hand position and the lack of eccentric contraction causes mouse elbow

Prevention

The most common mechanisms of injury for mouse elbow are imbalances. Therefore, balancing muscle contraction and activation is a simple, yet extremely effective preventative measure.

For all common gamer injuries including mouse elbow, we’ve created a comprehensive injury prevention program. Performing this exercise routine may help reduce your risk.

Concentric vs. eccentric muscle contraction

The lengthening phase of muscle contraction is the most important! For PC gamers, perform resisted extension exercises and stretches of the wrist and fingers and control the eccentric phase.

It is absolutely essential to perform the eccentric, or “down-phase” portion of these exercises slowly and under control!

On our injury prevention video, these exercises and stretches are:

Resisted finger extension

resisted finger extension
  1. Set up the finger band around the tips of your fingers, including your thumb
  2. Begin with your finger pads together. Then, open your hand as wide as you can
  3. SLOWLY, and under control, return to the starting position
  4. Repeat steps 2-3 for a total of fifteen (15) repetitions

Weighted wrist extension

weighted wrist extension
  1. Lay your forearm down on a flat surface with your palm facing downward
  2. Grab a dumbbell or other small, weighted object, and let your wrist hang over the edge
    Extend the dumbbell upward
  3. SLOWLY, and under control, return to the low, hanging position
  4. Repeat steps 2-3 for a total of fifteen (15) repetitions

Post-facilitation stretch, wrist extensors

wrist extensors
  1. Flex your wrists as far as you can, and place them on the ground
  2. For 10 seconds, press your hands into the ground as hard as you can
  3. After 10 seconds, try to lift your hands and fingers off the ground
  4. At the same time, lean backwards to stretch the extensor muscles of your forearms
  5. Repeat steps 1-4 for a total of three (3) sets

Agonist vs. antagonist muscle activity

Balancing the muscle activity at any joint will help keep muscles healthy. For PC gamers, extension of the wrist & fingers is the strenuous action; therefore, it is important to perform flexion exercises and stretches for the wrists and fingers for balance.

On our injury prevention video, these exercises and stretches are:

Weighted wrist curl

weighted wrist curl
  1. Lay your forearm down on a flat surface with your palm facing upward
  2. Grab a dumbbell or other small, weighted object, and let your wrist hang over the edge
  3. Curl the dumbbell upward, and return to the low, hanging position
  4. Repeat steps 2 and 3 for a total of fifteen (15) repetitions

Post-facilitation stretch, wrist flexors

wrist flexors
  1. Extend your wrists as far as you can, and place them on the ground.
  2. For 10 seconds, press your hands into the ground as hard as you can.
  3. After 10 seconds, try to lift your hands and fingers off the ground.
  4. At the same time, lean forward to stretch the flexor muscles of your forearms.
  5. Repeat steps 1-4 for a total of three (3) sets.

In addition to these mouse elbow-specific preventative measures:

Rehabilitation

To effectively resolve mouse elbow, it is important to first identify and correct the initial cause. For example, if you’re not performing the eccentric action of the extensor muscles or exercising the flexor 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.

Step 1: aggressive cross-friction massage

cross-friction massage

The provider should use a firm surface (thumb pressure or a knuckle, for example) to apply moderate pressure to the common extensor tendon and scrape perpendicularly across the tendon. 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.

Step 2: heavy eccentric loading

heavy eccentric loading

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 elbow, this would involve holding a weight (dumbbell or other small, weighted object) in the palm of the hand with the wrist extended and elbow flexed. In a slow, controlled manner, allow the elbow to open and wrist to drop—pulling the tendon.

Step 3: heat therapy

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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Disclaimer

This information is for educational purposes only and is not intended to replace the advice of your doctor. Esports Healthcare disclaims any liability for the decisions you make based on this information.

The information contained on this website does not establish, nor does it imply, doctor-patient relationship. Esports Healthcare does not offer this information for diagnostic purposes. A diagnosis must not be assumed based on the information provided.

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