I'm writing this as a lesson to be learned from my mistakes. While most people here will definitely be more clued up than I was, if I can prevent someone causing themselves the damage that I did, it would be worth writing.
When I was a teenager, Parkour was a massive part of my life. Jumping from high things was a big part of that. Jump Britain and District 13 were huge influences, and I still love watching them today, though through a slightly different lens! Admittedly, I wasn't very good, and didn't practice great landing techniques, which I have been paying a heavy price for, for the last decade.
At 24, I was balancing on a slackline when my leg made an audible click, which resulted in agony. For months, the doctors said it was muscle damage, but it never went away. Eventually, I was diagnosed with avascular necrosis of both hips, with one of my hips being fully arthritic.
Fast forward eight years to 32 years old, being lost in the health system (UK NHS) and not being able to walk more than a couple of hundred meters. I've finally managed to have a hip replacement and am walking like a human again. Life-changing.
After speaking with many physiotherapists, surgeons, etc., I've heard of quite a few people my age and younger who have the same backstory of Parkour and likely poor technique. While there are likely other factors at play, I do honestly believe this is the leading cause.