The woman was in collision with a white Mercedes Sprinter van on New Market Street, close to the WH Smith store.
Police were called to the incident by the ambulance service at 10.20am.
They said the woman was knocked to the ground as a result of the collision and is thought to have sustained a fractured hip.
She was taken to hospital.
The van, which was backing up when it collided with the woman, is understood to have been delivering to a nearby business.