The man was taken to hospital as a precaution after he was knocked from his chair, sustaining minor cuts and bruises, but was later released.
A St John spokeswoman said the woman had not suffered any medical event and was talking coherently to ambulance staff tending to her after the crash.
She was taken to hospital with moderate injuries.
She lost control of the Mazda Demio as it exited City Rd about 10.20am.
It travelled, at high speed, across the busy intersection at Highgate, up on to a garden area in the shopping area and crashed into the plate glass window of the Roslyn Physiotherapy Clinic, where patients were waiting and staff were working.
Clinic co-owner Brett Woodley said it was incredible the injuries were not more serious.
He said a "crazy" sight greeted him when he ran out of a treatment room.
Chairs in front of the window had been shunted across the room and had, in turn, pushed the reception desk back, a man was lying on the floor and there was glass everywhere.
The receptionist saw the car coming and ducked to the side, which had been lucky because large shards of glass from the window were imbedded in the wall behind the reception desk, he said.
"This could have been so much worse."
It was "unbelievable" the car had travelled so far out of control, across an area normally full of traffic, pedestrians and people sitting on the garden seats, without hitting anyone.
The car had first hit a veranda post, which had probably stopped it from going further into the waiting room, he said.
"Everyone's very, very lucky. We're just thankful no-one was seriously injured."
A motorist, whose vehicle was clipped by the out-of-control Demio as it passed through the intersection, said the woman's car was "going like the clappers".
Sergeant Ed Baker said police were investigating, but as yet did not know what had happened, Mr Woodley said the clinic would reopen today.
