Patricia Field, 88, of The Spinney, was Christmas shopping in Priory Meadow Shopping Centre when the incident happened.
Police said they received a report of a collision involving a man on a mobility scooter and a woman.
Patricia said: “I was walking into the shopping centre and had just gone past Ernest Jones jewellers when suddenly there was a massive shock into the back of my spine.
“I hit the ground very hard.”
Patricia said her right arm was broken in two places and she suffered a head injury, back injury and a cut foot.
She said: “I was also sick and had a lot of chest pain. People ran to pick me up off the ground.
“When I hit the ground I knew my arm was broken. The security guards were there and another man helped me up. A security guard spent half an hour with me.”
Patricia was taken to hospital and discharged the next day.
She said: “My arm was in a cast for five weeks and because of this it took several hours to put clothes on, wash hair and so on.”
The incident happened on November 26 at around 12.30pm, Patricia said, when she went out to do her Christmas shopping.
She added police officers came to her home to take pictures of her injuries on her arm and legs after the matter was reported to the police.
Patricia said: “I have a heart condition and osteoporosis as well and was told it would take three months for my arm to heal properly.”
A Sussex Police spokesman said: “Police received a report of a collision involving a man on a mobility scooter and a woman in Priory Meadow Shopping Centre, Hastings, around 12.30pm on Friday, November 26. The woman was taken to hospital with serious arm injuries.
“Enquiries are ongoing and anyone who saw what happened or who has any other information is asked to contact police online or by calling 101 quoting serial 373 of 29/11.”