Fundamental movements of the wrist are movements of the hand
as a unit. They occur chiefly at the radiocarpal joint but involve
the midcarpal and intercarpal joints when flexion or hyperextension
is carried to the limit of motion.
Performed by the flexors carpi radialis, carpi ulnaris, and digitorum
superficialis, with possible help from the palmaris longus, flexor
pollicis longus, and flexor digitorum profundus.
Performed synchronously by the extensors carpi radialis longus,
carpi radialis brevis, carpi ulnaris, and extensor digitorum, with
possible help from the pollicis longus and extensors indicis and
Performed by the extensors carpi radialis longus and brevis and
flexor carpi radialis, with possible help from the abductor pollicis
longus and the extensors pollicis longus and brevis.
Performed by the extensor carpi ulnaris and the flexor carpi
For a better understanding of all the actions of the finger and
thumb muscles, they should be studied both on the skeleton (using
elastic bands to represent muscles) and on another person. Particular
attention should be paid to the relation of each muscle to every
joint it crosses, to the muscle’s line of pull, and to
the leverage involved.
As an aid to recognizing the secondary actions of the muscles,
a record of all the joints crossed by all the finger and thumb muscles
is included here.
of the Fingers
All five of these muscles cross four sets of joints: wrist, carpometacarpal,
metacarpophalangeal, and proximal interphalangeal. The extensor
digitorum and extensor digiti minimi also cross both the elbow and
the distal interphalangeal joint, making a total of six joints crossed.
The flexor digitorum superficialis crosses the elbow but not the
distal interphalangeal joint, and both the extensor indicis and
flexor digitorum profundus cross the distal interphalangeal joint
but not the elbow.
of the Fingers
Of these six muscles, only the abductor digiti minimi and flexor
digiti minimi brevis cross both the carpometacarpal and the metacarpophalangeal
joints. The two interossei muscles, dorsales and palmaris, and the
lumbricales cross only the metacarpophalangeal joint. The opponens
digiti minimi, like the opponens pollicis, crosses only the carpometacarpal
joint. The two work together in the cupping action of the palm as
well as independently in other opposition movements.
of the Thumb
All four of these muscles cross both the wrist and carpometacarpal
joints, and all but the abductor pollicis longus also cross the
metacarpophalangeal joint. The extensor and flexor pollicis longus muscles
cross the interphalangeal joint as well. The thumb, of course, has
no second interphalangeal joint.
of the Thumb
All four of these muscles cross the carpometacarpal joint, and
all but the opponens pollicis cross the metacarpophalangeal joint.
The muscular action of the fingers is given in terms of the movement
of each phalanx. Movement of the proximal phalanx occurs at the
metacarpophalangeal joint, of the middle phalanx at the proximal
interphalangeal joint, and of the distal phalanx at the distal interphalangeal
joint. For convenience in referring to individual fingers, numbers
are assigned as follows: 2 for the index finger, 3 for the middle
finger, 4 for the ring finger, and 5 for the little finger.
Flexed by the lumbricales manus (all fingers), interossei palmaris
(palmar interossei) (2,4,5), interossei dorsales manus (2,3,4),
flexor digiti minimi brevis (5), and opponens digiti minimi (5), with
possible help from the flexors digitorum superficialis and profundus.
Flexed by the flexor digitorum superficialis, which acts on all
four fingers and at the same time contributes to flexion of the
Flexed by the flexor digitorum profundus, which also acts on
all four fingers and at the same time contributes to flexion of
the proximal and middle phalanges.
Extended by the extensor digitorum (all fingers), extensor indicis
(2), and extensor digiti minimi (5). The extensor digitorum is also
able to help extend the middle and distal phalanges.
Middle and Distal
Extended by the lumbricales manus (all fingers) and interossei
dorsales manus (dorsal interossei) (2,3,4). The abductor digiti
minimi (5) and the extensor digitorum (all fingers) are also able
to help extend the middle and distal phalanges at the same time
that they are extending the proximal phalanx.
Note: When all the fingers flex
or extend, the antagonists relax in reciprocal innervation. However,
if a single finger moves, the antagonists will contract in an attempt
to keep the other fingers still.
Abduction is brought about by the interossei dorsales manus (2,4)
and abductor digiti minimi (5), and adduction by the interossei
Radial and ulnar flexion of the middle finger is performed by
the interossei dorsales manus (3).
The fifth digit, or little finger, being at the outer margin
of the hand, has greater freedom of movement than do the other fingers.
Through the action of the opponens digiti minimi, the metacarpal bone
of this finger can engage in a slight degree of opposition at the
carpi metacarpal joint. Together with the thumb, it participates
in this movement when the hand is “cupped,” as
when scooping up water, and also when the tip of the little finger
is brought forcibly against the tip of the thumb.
The muscular action of the thumb is given in terms of the movements
of the metacarpal bone and the two phalanges, proximal and distal.
The metacarpal is flexed and hyperflexed after being slightly
abducted by the flexor pollicis brevis and the adductor pollicis.
The flexor pollicis longus also participates and becomes more dominant
when the action is full flexion (Basmajian and DeLuca 1985).
Performed chiefly by the abductor pollicis longus, with help
from the opponens pollicis, the abductor pollicis brevis, and the
extensors pollicis longus and brevis.
Four muscles are responsible for this movement, two from the
forearm, the abductor pollicis longus and the extensor pollicis
brevis, and two from the thenar eminence, the abductor pollicis brevis
and the opponens pollicis. Under some conditions these may be helped
by the flexor pollicis brevis.
This movement is performed mainly by the adductor pollicis, with
some help from the flexor pollicis brevis and, in certain positions,
from the extensor pollicis longus.
This action is performed mainly by the opponens, but with appreciable
help from the flexor pollicis brevis. As opposition is not a single,
well-defined movement but varies according to the finger that is
being opposed and to the exact position of that finger, the muscles
controlling the thumb must adapt to the demands of the situation.
This includes the action of the phalanges as well as that of the
The flexor pollicis longus flexes both of the phalanges. Additional
flexors of the proximal phalanx include the flexor pollicis brevis
and the adductor pollicis, with help from the abductor pollicis
brevis when necessary.
The extensor pollicis longus extends both of the phalanges. This
is joined by the brevis in the extension of the proximal phalanx.
The plane in which flexion and extension of the thumb phalanges
occurs is determined by the position of the metacarpal bone of the