My horses were family pets but I still rode them in cross country events - admittedly nowhere near as risky as National Hunt racing. The horses enjoyed the events as much as I did.
I had one much-loved horse that hit a solid fence then 3 days later her leg shattered - a 'star' fracture caused by the impact.
You could argue that I shouldn't have ridden her in these events - but that was the whole point of having her and she had a great time and without human foresight could not have felt worried that she was at risk.
Because she was a member of the family we sent her for surgery to mend the fracture - we couldn't face having her put down and wanted to save her life. She endured 4.5 hours of surgery then 4 months confined to a stable. Even this was only possible because she had broken a small bone (her pastern which is the part just above the hoof.)
Horses' bones don't heal anything like as well as ours do which is one of the reasons that animals with broken legs are usually put down.
When my horse was eventually turned out in a field for the first time she bucked, leaped and galloped for nearly half an hour till she was soaked with sweat and exhausted. She was so exuberant - she just wanted to run and run after being cooped up for so long.
With the benefit of hindsight I'm not sure that I did the right thing. She did enjoy 15 years of retirement, but was very bored out in the field. Every time I took her out she was so excited. During those 4 months confined in a 12 foot square prison she must have been going mad.
She wasn't a Thoroughbred so could be retired to a paddock with shelter at night. You can't leave racehorses out in fields 24/7 over winter.