Hello there muscle twitching can be bcos of various reasons...usually less serious cause like high stress or tension,nutritional deficiency, overuse of caffinated drinks/smoking or even some medications......however joint pain is usually not associated with twitching.... you need to give me a detail medical history of your wife..also her blood test to determine the level of iron,calcium,B12,D3,RA factor needs to be carried out along with Thyroid.... sometimes small factors like lack of sleep or blood causes twitching of thumb...while some times twitching can be a sign of some major underlying problem. Regards,Take care.