Very Interesting Champ, Just goes to show how we really can't know what has happened without seeing the patient. And as much as we can offer advice over the internet the best thing to do is to get that objective examination done from a professional and get those scans that are needed to diagnose.

Don't think about the arthritis aspect mate, just have fun for as long as you can... Knee replacements are common nowadays so just imaging in 40 years when you'll need one how good they'll be.

Have a good one