Hi, My problem is I believe, a little abnormal. It started last spring, I was in 8th grade. There would be random days where I couldn t straighten one my arms. Slowly throughout the day my mobility would come mostly back. This fall, it happened again a few times with my arm, but not have transferred to sometimes my wrist and lately my knee. It normally happens now more at night or if I have been sitting at a desk for a extended period of time occasionally. Thanks so much. (Please excuse in grammatical mistakes. )