The interosseous (in-tur-AW-see-us) muscles fill the
space between the four metacarpal
bones in the hand (Figure 6.43) There are two sets of interosseous muscles. The four dorsal
interosseous are accessible from the back of the
hand. They move the index, fourth, and fifth fin- gers away from the middle finger and move the middle finger from side to side. The three palmar
interosseous muscles are accessible through the
palm. They bring the fingers together by moving the index, fourth, and fifth fingers toward the middle finger. All seven interosseous muscles have a role in the grasping function and in the many subtle manipulations of the fingers and hand.
Trigger points in the interosseous muscles refer pain to the sides and undersides of the fin- gers and the last finger joints. They contribute to finger stiffness, weakness, and awkwardness. Interosseous muscles can cause numbness in the fingers when they com-
press the digital nerves, which also lie between the metacarpal bones. The dig- ital nerves supply the fin- gers. (1999: 786-788)
The bulky, highly developed first dorsal interosseous muscle makes up most of the web between the index finger and thumb (Figure 6.44). Its trigger points have a much wider referral
Elbow, Forearm, and Hand Pain 131
pattern, sending pain to the palm, the little finger, the back of the hand, and all surfaces of the index finger. Occa- sionally, they refer a deep ache to the entire ulnar (pinky side) side of the hand. To locate the first dorsal interosseous
muscle, see and feel it bulge up as you press the index fin- ger against the thumb (Figure 6.45).
If writing with a pen or pencil gives you pain in the underside of your middle finger and its last knuckle, look for a trigger point in the second dorsal interosseous muscle,
between the metacarpals of the index and middle fingers. This muscle helps the middle finger push against the thumb
to grip the pen between them. Fixing writer's cramp is often
only a matter of finding the hand muscles that have the trig-
ger points. The short thumb muscles and the first dorsal interosseous are the usual source of writer's cramp, but don't overlook the others.
The interosseous muscle of the little finger is located on the outer edge of the hand. Trigger points in this muscle can refer pain to the little finger but aren't usually the source of
pain in the edge of the hand. Keep in mind that pain can be sent to the fourth and fifth fin- gers by many muscles, including the serratus posterior superior, serratus anterior, latissimus
dorsi, pectoralis major and minor, extensor carpi ulnaris, flexor carpi ulnaris, and triceps. Numbness in these two fingers and in the ulnar side of the hand comes from the flexor carpi
ulnaris, pectoralis minor, triceps, teres minor, and scalenes. (1999: 794)
Heberden's nodes, bumps on the sides of the last knuckles, are thought to originate
with
trigger points in overused interosseous muscles. Bumps on the middle knuckles are called
Bouchard's nodes. It may be possible to eliminate both kinds of nodes by trigger point
therapy
to the interosseous muscles, if intervention comes early enough. Even if fully developed, nodes can often be reduced. The same stresses in the interosseous muscles that create nodes
on the knuckles may contribute to the development of arthritis. (1999: 786-792)
Players of musical instruments like the piano, violin, or guitar, who must often spread their fingers to extreme positions to reach notes, are especially prone to overuse of the interosseous muscles. Repetitive powerful gripping with the fingers on the job or in a sports
activity also risks overloading these small muscles.
Your computer mouse puts both the first dorsal and first palmar interosseous muscles at extreme high risk of overuse if you use your index finger to click the buttons. The mouse also predictably overworks the extensor indicis
and part of the extensor digitorum, which work together to
lift the finger between down strokes. If you position your mouse to the side of your keyboard, you're likely to create
trigger points in your infraspinatus, teres minor, trapezius,
rhomboid, and anterior deltoid muscles because of the continuous outward rotation and forward flexion of the arm. A good solution to the mouse problem may be an ergonomic keyboard with a built-in touch-pad mouse. Some laptops have a touch pad centered in front of the 6.46 Dorsal interoseous keys, which is an excellent way to take the strain off many
Figure 6.46 Dorsal interosseous massage with supported thumb muscles.
Figure 6.45 Locating first dorsal interosseous by isolated
224 The Trigger Point Therapy Workbook
Fig. 6.47 Eraser massage of interosseous
The tip of a supported thumb can be used to massage the interosseous muscles (Fig- ure 6.46). Deeper massage can be done with a wedge-shaped rubber eraser, held in a small spring clamp to save your fin- gers. Figures 6.47 and 6.48 show two different kinds of erasers that can be found every- where. One is a big pink eraser;
the other fits over the end of a
shortened pencil, which is then
gripped in the clamp. The inex-
pensive plastic spring clamp
shown in the illustrations can be found at many variety, department, and hardware stores. Massage the thick first dorsal interosseous by pressing it against the metacarpal bone
with the supported thumb (Figure 6.49). It works well to massage this muscle by pinching the web, but it can be extremely tiring for the thumb mus-
cles of the hand doing the massage.
Trouble with the interosseous muscles can be difficult to resolve. They're not easy to massage and your activities may be keeping them under continuous stress. Give seri- ous thought to changes you can make in the way you use your hands that will give these special muscles a break. You may even want to think about a job change. In severe cases, the only solution may be to have your trigger points
injected by a physician in the approved Travell and Simons manner.