Track work rider Riharna Thomson is recovering from surgery in Canberra Hospital after suffering serious head injuries in a fall.

Thomson's ride Chosen Prayer broke down during a gallop at Canberra's Thoroughbred Park on Tuesday morning, dislodging the jockey and resulting in her mount being euthanised.

She was taken to hospital for emergency surgery and was recovering with family by her bedside.

Worksafe ACT and the Canberra Racing Club have launched investigations into the accident.

Chosen Prayer, a five-year-old mare trained by Keith Dryden and Scott Collings, raced 26 times and recorded four wins, her last start was a fourth at Canberra in the Open Handicap on February 19.