Evans was riding Mount Rock, who was fatally injured, when he appeared to clip heels with the horse in front of him, bringing down Richardson on Just Hiss.
Ripon clerk of the course James Hutchinson said: "Nathan had a little bit of concussion so he's gone to hospital for further examination."
He went on: "Rachel had pain in her left shoulder and she is going to get that X-rayed."
Tim Easterby, trainer of Just Hiss, said: "She might have done a collarbone but it could have been a lot worse.
"Nathan is very sore indeed. He's very shook up."
The news came on the back of popular sprinter Jack Dexter suffering a fatal injury earlier in the day.