As I mentioned before - "life" can produce repetitive motion injuries. Consider how much time you spend in front of a computer, or using a mouse. What do you do that promotes flexiblity in your smaller joints and overall strength ? If you haven't really explicitly done much to focus or be aware of mobility & flexibility, IMO it doesn't take that much to just start experiencing stiffer joints as you get older The body simply can't heal as quickly as it did when you were producing optimal levels of all the "youthful" hormones. I may have mentioned - I was at my absolute peak in 2010 - I was 45 years old and had just won a national qualifier in women's bodybuilding w/ intent to spend the next year training for Nationals. A week after winning my show, a shoulder tweak I had done the week before the show blossomed into a really big ligament elasticity issue that I'm still dealing with, and literally every joint I ever had a pain in all decided to go to shit at once. Knees were tweaked, wrists hurt like a bitch, forearm tendonitis, really painful tendonitis at the bicep insertion, lower back, ankles. You name it, it hurt. With time off to heal, a lot of chiro / massage / therapy and a lot less heavy lifting, things are better. But I focus much more on mobility / flexibility warm up before I do anything in the gym and plan to incorporate a lot of yoga / pilates type stuff into my routine once I complete (yet another) cross-country relocation for my job.
It is never "too late" to start working your body the way it was designed to be used. I love this quote from Jack Lalanne: "The only way you can hurt the body is not use it. Inactivity is the killer and, remember, it's never too late." What you may find is that you need to spend a little more time warming up and not dive straight into lifting. This isn't a bad thing. I keep thinking of this guy I used to train with - he was a big guy, around 35 years old, long time weight lifter, played some football in HS. He was always bitching about something hurting. One day he goes, "I'm thinking about getting a hip replacement...." I looked at him, being 10 years older than him and having aches & pains, but at least fully manageable, and said "My MOTHER had a hip replacement... she's 75 and has osteoporosis issues...." Really? Yea, sure people take a beating in the stuff they choose to do, but when you're not 20 years old and don't have to worry about paying the mortgage and funding your retirement, its ok to do 1000 lb leg presses cold. But it's not an intelligent habit to form. Train smarter, not harder, and then you can also train longer. Ref the several bodybuilders in their 70s & 80s - and some of them started in their 60s & 70s, not their 20s.
One thing you will find most people in the bodybuilding community have is a great eye to the future and don't get hung up on where they are now. Everyone has to start somewhere, but as you do it, you also learn that the gym allows you to make a new PR, literally every day. Look forward to what you can do w/ consistency, persistance and the conditioning that comes with that, and you will continually be amazed at where you can go, as opposed to worrying about what you are "stuck with" now.