The only factors I know about bone strength have to do with bone thickness and density, which is related to diet and exercise, and hormonal factors, but also to genetic variations.
Not aware or easily able to find anything about muscle tears. I would guess that some of the same genetic variations associated with difference in muscles’ responses to training discussed here would play roles however.
You really need to compare more identical types of injuries. A “cohort” study of fifty people with broken wrists and their time to return to work, pain level, etc. would be valid, but a study of fifty people with a random assortment of injuries would be pretty much pointless.
I can easily picture ways where someone is holding a spike and gets whacked with the sledgehammer and not be severely injured. I’m thinking long spike held near the top, hand gets hit with a somewhat glancing blow and the hand is able to be pushed aside and down a few inches rather than being mashed with a direct hit while on a hard surface.
As for knees, it just takes one twist in the wrong way to get sprained. Most people would consider professional football players to be well-conditioned, but it only takes one tackle from the side to blow out the ACL and have that player out for the season.
From a practical viewpoint as someone with hypermobility, while hypermobility provides increased risk of some sorts of injury, I also contend that the additional mobility can in some cases prevent far more serious injury, due to tendons and ligaments stretching before tearing. I twisted my ankle in a drain on our driveway while moving a heavy wheelie bin - when it happened, I thought I had broken the ankle, but I was still moving on it (carefully) the next day and the ankle recovered without major issues. Similarly, both my son and I have issues with shoulders - my son fell over outside his uni halls. Popped his shoulder out. Stood up, flexed the muscles in the joint and the ball popped back into place with a click his friends could hear. Then he fainted. However, the injury was nowhere near as serious as a full dislocation can be, and did not require much additional treatment (ice, anti-inflammatories, and some physio once the soft tissue injury abated).
I am very careful, though. I work out, and place special emphasis on rotator cuff and ankle stability exercises - I’d rather support the joint with muscle than suffer injury.
Interestingly, my son (who suffers from cluster migranes) found research that indicates that hypermobility may be associated with insensitivity to some analgesics, which may explain why he has to head for the strongest painkillers the doctors give him as a starting point during an episode.
I’m curious about this as well. I have a co-worker who has serious complications from the most minor of things and is constantly taking time off work. The latest was two weeks off for a bruise on her leg. Seriously. We weren’t able to get an explanation from her that made sense or would explain why it was so serious that she needed two weeks off. Prior to that it was two weeks off for having her wisdom teeth removed. Her explanation for that was she has a “bad immune system.” Either she just doesn’t want to come to work or she does have some other medical condition. She’s overweight and eats a lot of McDonald’s (it’s her breakfast and lunch virtually every day) so possibly nutrition has to do with it even though she’s still in her 20s.
You should find your self a rock and roll band that needs a helpin’ hand.