Can tendonitis/tendonosis cause fingers to feel stiff ? been checked for ra and that's clear.

Unlikely: A tendonitis of the hand would cause pain, swelling and tenderness along the flexor tendon of usually one finger. A stenosing tenosynovitis would cause a trigger finger. Isolated stiffness would not be a symptom. Carpel Tunnel Syndrome, which usually causes numbness and tingling in the hand, can occasionally present itself just with numbness in the thumb and index finger.