Patients with neck pain and discomfort may complain of pain in the thumb region with difficulties in moving the painful thumb muscles.
Pain at the base of the thumb may be due to arthritis at the joint between the wrist bone and the knuckle bone known as the carpometacarpal joint. Arthritis at this joint is very common. Arthritic pain of this joint at the base of the thumb is made worse when there is nerve related pain and spasm in the muscles that cross the carpometacarpal joint (joint between the thumb wrist bone and the thumb knuckle bone).
Treatment of thumb pain must involve treating all muscles that participate in moving the thumb in all its many capable movements of flexion, extension, abduction, adduction and opposition.
The many complex movements of the thumb are essential in producing fine manipulation such as writing, picking up small objects, turning the key, stitching, knitting cutting up food, turning the doorknob, etc.
Thumb flexion consists of moving the thumb along the plane of the palm.
Muscles responsible for performing this motion include:
- flexor pollicis brevis (superficial head supplied by the median nerve and the deep head supplied by the ulnar nerve). This muscle is supplied by the C8 and T1 nerve roots.
- extensor pollicis longus supplied by the radial nerve (C7, C8).
When the flexor pollicis brevis is not functioning, the supplementary action of the extensor pollicis longus muscle together with that of the flexor pollicis longus supplied by the anterior interosseous branch of the median nerve by causing simultaneous flexion of the tip of the thumb will be able to flex the thumb along the plane of the palm.