De Quirvain's tenosynovitis - A condition where the thumb tendons get inflamed and irritated from repetitive movements in the wrist.
Common for mothers due to pregnancy, breastfeeding and fluid retention, but also in tradies, gardeners (and Osteo's!) from repetitive movements of the hands.
Treatment may involve
soft tissue release
upper extremity and shoulder biomechanics addressed
understanding ergonomics of the task involved and modify as necessary
bracing and medication if needed
Try to keep your thumb and index fingers as close together as you can! Mums (and dads) keep swapping sides for lifting and feeding
A lot of people get relief without surgical intervention. See your osteo :)