Which of the following is NOT a common musculoskeletal disorder (MSD)?

• A. Carpal tunnel syndrome
• B. Tendonitis
• C. Photokeratisis
• D. Lower back strain

Answer: (C)

Photokeratitis is not a musculoskeletal disorder; it’s an eye injury caused by UV exposure from the welding arc, often called welder’s flash. MSDs involve the muscles, tendons, nerves, or spine and come from repetitive motions, overuse, or awkward postures. Carpal tunnel syndrome arises from repetitive hand and wrist activity, compressing the median nerve. Tendonitis is inflammation of a tendon from overuse. Lower back strain results from lifting or awkward bending that strains the back muscles and spine. So the item that does not fit as a common MSD is the eye condition, photokeratitis, because it affects the eyes, not the musculoskeletal system.