The victim was walking to Brownhills to catch another bus into Walsall town centre when she was targeted by cyclist Daniel Taylor, Wolverhampton Crown Court heard.
The 20-year-old struck on the foot and cycle path running alongside the A5 to the Park View Medical Centre at Chester Road North, said prosecutor Miss Alka Brigue.
Taylor grabbed the strap of her bag as he came alongside her at around 9.30am on August 18.
He tugged so hard that she was hurled to the ground but clung on to the bag until he trod on her hand forcing her to let go, said Miss Brigue.
Taylor then rode off with the bag but two women witnesses alerted police quickly enough for them to be able to catch him and recover the stolen property.
Nigel Ford, defending, said: "This was a moment of madness for which he is now going to pay a significant price.
"He is extremely sorry for what happened and has no idea why he did this."
Taylor, of Norwich Road, Alumwell, Walsall, admitted robbery and having the drug Mkat that was found in his possession when he was arrested. He also tested positive for cocaine.
He was ordered to be detained in a Young Offenders Institute for 20 months by Judge Michael Dudley.