College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which muscle would likely produce pain with radial deviation in a patient with de Quervain's tendonitis?

1. Extensor digitorum

2. Extensor pollicis longus

3. Flexor digitorum longus

4. Abductor pollicis longus

The correct answer is: Abductor pollicis longus

The muscle likely to produce pain with radial deviation in a patient with de Quervain's tendonitis is the Abductor pollicis longus. This condition involves inflammation of the tendons that run through the first dorsal compartment of the wrist, specifically affecting the abductor pollicis longus and the extensor pollicis brevis. When a patient performs radial deviation, the abductor pollicis longus is actively engaged to facilitate movement away from the midline of the body towards the radius. In the context of de Quervain's tendonitis, this muscle becomes inflamed and sensitive, leading to pain during activities that involve this motion. Other muscles listed, such as the extensor digitorum, extensor pollicis longus, and flexor digitorum longus, are not primarily involved in the specific mechanics of radial deviation or are located in different compartments, thus making them less likely to be associated with the pain experienced in de Quervain's tendonitis during radial deviation. The specific targeting of the abductor pollicis longus in this condition highlights its role and sensitivity during the painful movement.