The muscles that primarily cause ulnar deviation (movement of the hand towards the little finger) are the flexor carpi ulnaris and the extensor carpi ulnaris.
Muscles Involved in Ulnar Deviation
Ulnar deviation, also known as adduction of the wrist, is a movement that relies on the coordinated action of several muscles in the forearm and wrist. The main contributors are:
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Flexor Carpi Ulnaris (FCU): This is the most powerful wrist flexor and a primary ulnar deviator. It originates from the medial epicondyle of the humerus and inserts onto the pisiform bone, hamate bone, and the base of the fifth metacarpal.
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Extensor Carpi Ulnaris (ECU): This muscle is located on the posterior side of the forearm and is the primary extensor responsible for ulnar deviation. It originates from the lateral epicondyle of the humerus and inserts onto the base of the fifth metacarpal.
Synergistic Action
While the FCU and ECU are the main muscles responsible, other muscles can assist in ulnar deviation, especially when combined with other wrist movements. These include:
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Flexor Digitorum Profundus & Superficialis: These long finger flexors also have tendons that cross the wrist, and their contraction can contribute to ulnar deviation, albeit to a lesser extent.
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Extensor Digitorum: Similar to the flexors, the extensors of the fingers can contribute marginally.
Importance of Balance
Proper wrist function relies on a balance between the muscles responsible for ulnar and radial deviation (movement towards the thumb). Imbalances can lead to conditions like carpal tunnel syndrome or tendinopathies.
In summary, the flexor carpi ulnaris and extensor carpi ulnaris are the key muscles responsible for performing ulnar deviation.
