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A B M P m e m b e r s ea r n F R E E C E h o u r s by rea d i n g t h i s i s s u e ! 61 PATHOLOGY CMC joint arthritis is described as the erosion of cartilage between the first metacarpal and the trapezium. There can be different mechanisms that cause CMC arthritis, such as ligament laxity, previous injury, and overuse. 4 As massage therapists, we continually use our hands and, on many occasions, our thumbs during treatment sessions. However, we may not always be mindful of proper body mechanics and the stacking of our joints, thus inadvertently contributing to the wear and tear of our CMC joint. An adduction contracture of the thumb causes difficulty in its ability to abduct and rotate and, in some cases, may also limit the f lexion of the fingers. 5 Daily activities that may be affected by CMC arthritis include holding and turning a key, lifting a pot or pan, holding a toothbrush, and turning a door handle, among others where pinch and grasp are required. JOINT PROTECTION AND ERGONOMICS As massage therapists, we need to preserve our most important commodities: our bodies and hands. We often read about proper positioning of the table for maximum force and using our core to generate enough force for massage techniques, stacking our joints, leg stance, and standing over the client, to name a few. We can also focus on using our stronger joints and muscles, such as our forearms and elbows. During pinpoint work, such as on the neck, hand, and/or areas with specific trigger points that need to be addressed, we tend to rely more on our hands, especially our thumbs. ANATOMY The CMC joint of the thumb is a biconcave-convex saddle joint, where the first metacarpal of the thumb and the trapezium carpal bone articulate. 1 It is known as a saddle joint because of its shape—the articular surface is concave in one direction and convex in the other. There are 16 ligaments that support the CMC joint of the thumb. The two that provide the most support are the dorsoradial and the volar beak ligaments. The volar beak ligaments were once thought to be the most prominent stabilizers of the CMC joint; however, the dorsoradial ligaments are now thought be the most important in providing stability to the CMC joint. 2 The thumb is an extremely mobile joint, as demonstrated by movements of opposition and reposition (combinations of actions), f lexion and extension (which occur in the frontal plane), and abduction/adduction (which occur in the sagittal plane). The extrinsic muscles that control the movements and support the thumb, in which the proximal part of the muscle attaches on the forearm and the distal part attaches to the thumb, are the extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus, and f lexor pollicis longus. The intrinsic muscles, where the entire muscle and its attachments are on the hand and attach to the thumb, include the abductor pollicis brevis, opponens pollicis, f lexor pollicis brevis, and adductor pollicis. The intrinsics and extrinsics work together to produce efficient motion. 3 An additional hand muscle—the first dorsal interossei—helps stabilize the thumb and works in conjunction with the opponens pollicis to stabilize it during pinching. Getting a Diagnosis If you do have pain in your thumb, you may want to see an orthopedic hand specialist to get a formal diagnosis, since there are other conditions that can mimic CMC joint arthritis. The orthopedist may refer you to see a hand therapist, occupational therapist, or physical therapist. The hand therapist may be able to make you a custom splint for more support and stability, as well as provide additional exercises, suggestions, and feedback. KEY POINTS • Multiple exercises and techniques can help improve thumb pain. • Using various products designed to protect the thumbs can help limit or prevent injuries such as CMC.