ST. LOUIS — "Smartphone Thumb" is plaguing more people. Dr. Richard Lehman says that the condition that doctors used to only see in factory workers is becoming more widespread. The pain that comes from the repetitive movements of texting. It's actually tendinitis, when the tendon that bends and flexes the thumb becomes inflamed. More and more people are complaining about this type of pain in their thumb each year, say doctors at the Mayo Clinic.