Interossei of the Hand: Pain Pattern and Treatment
The interossei are the small muscles between the long bones of the hand, four on the back that spread the fingers and three on the palm side that draw them in. The largest is the muscle in the web between the thumb and index finger, which works with every pinch. Their documented pattern is pain along the side of one finger from the knuckle to the tip, and, from the thumb-web muscle, pain along the index finger and into the back of the hand and the palm. When one finger aches along its side and the joints are normal, this is the muscle to check. This page relates to the thumb muscles page.
Attachments and action
Origin: Dorsal interossei: the adjacent sides of the metacarpals, two heads each. Palmar interossei: the sides of the second, fourth, and fifth metacarpals facing the middle finger.
Insertion: The bases of the proximal phalanges and the extensor expansions of the fingers.
Action: Dorsal interossei spread the fingers; palmar interossei draw them together; both bend the fingers at the knuckles and straighten them at the joints beyond, and the first dorsal interosseous drives a pinch.
Where the pain is felt: Along the side of one finger from the knuckle to the tip. From the thumb-web muscle, along the thumb side of the index finger, into the back of the hand, and deep into the palm. Between two metacarpals on the back of the hand.
Common causes: Pinching and gripping tools; scissors and pliers; texting and scrolling with a pinch grip; knitting and needlework; playing a stringed instrument; a mouse gripped between thumb and index finger; a cast that held the fingers together.
Patients say: "It hurts along the side of my index finger." "The web of my thumb is tender to pinch." An ache between two knuckles on the back of my hand. "They said early arthritis, but the X-ray was clean."
When to get evaluated: Finger joints that are swollen, warm, and stiff for more than an hour in the morning, in several fingers or both hands, need medical evaluation for inflammatory arthritis. Wasting of the thumb web with weakness spreading the fingers points to the ulnar nerve and needs a nerve conduction study. A finger that is crooked or bruised after a jam needs an X-ray.
How this muscle is examined and treated
Examination tests finger spreading and finger squeezing against resistance, presses between the metacarpals from the back of the hand and pinches the thumb web for the point that reproduces the pain along the finger, and checks the finger joints to separate this from arthritis and the thumb web for wasting. Needling here addresses the muscles between the metacarpals from the back of the hand. Assessment and treatment happen in the same visit.
Related conditions
TendinitisChronic Pain PatternsSports & Performance Injuries
This page is educational. It describes muscle referral patterns commonly associated with pain; it does not diagnose your condition. Individual patterns vary. For evaluation of your specific pain, see a licensed clinician. Seek immediate medical care for emergencies. Eugene Baek, L.Ac. · New Jersey License 25MZ00080600