Patients with neck pain and discomfort may complain of thumb pain with difficulty in moving the painful thumb into extension.
Extension of the thumb is the movement in which the thumb moves away from the plane of the palm.
The movements of the thumb in extension are primarily performed by:
- extensor pollicis longus supplied by the posterior interosseous branch of the radial nerve (C7, C8)
- extensor pollicis brevis supplied by the posterior interosseous branch of the radial nerve (C7, C8)
The extensor pollicis longus: Main action is to straighten the tip of the thumb and secondary action is to straighten the joint between the wrist bone and the knuckle bone known as the metacarpo-phalangeal joint.
The extensor pollicis brevis: Main action is to straighten the thumb at the metacarpophalangeal joint. Its secondary function is to straighten the thumb by acting at the joint between the wrist bone and the knuckle bone known as the carpometacarpal joint.
Associated arthritis with pain at the base of the thumb is very common. The pain can be made worse by pain and spasm in all muscles that cross or act upon the carpometacarpal joint of the thumb.