I think it's a given that our bodies all carry different specific chronic issues based on our patterns of use, both on and off the board, genetics, etc. That being said, I feel as if I have made some recent progress on the journey of trying to unravel my own physiological shit and I'd like to share so that OP or any other ppl with similar problems might find useful information.
I'm 30 and have been skating intermittently since I was about ten, a few years on, a year or two not skating so much, life happens, you already know all the shit. I've been "on" since age 25 and hopefully until I die or am in a walker. Around this time started noticing some knee pain in my right leg (I skate regs), nothing too severe, just a tightness/discomfort when the joint was at a slight bend (maybe from like 150 to 120 degrees). For the most part I just dealt with it. I'd just use adrenaline and ibuprofen to keep moving and then just be really wrecked for the next day. There were times when it was worse and times when I wouldn't even notice it. I figured I had just done some minor ligament damage and that was that.
This past year I was noticing that the pain has been the same all this time. You'd think it would get worse by now because I skate as much as I can these days and certainly am not getting younger. I started looking more into biomechanics and anatomy. It turns out that a lot of chronic joint pain arises from the cycle of weakness->imbalances->overcompensation. It's a feedback loop that imprints itself in your mind-muscle connections and results in poor mechanics. A lot of the pain specific to the knee is actually related to the quadriceps, hamstring, and calve. You may be feeling it in your knee, but that because its's where the muscles terminate and anchor to the skeleton.
For instance, pain on either side of the knee might be from the insertion points of the quad, which is a huge and powerful muscle. If the other muscles in the system are not doing enough to absorb impacts, then those thin connection points are bearing the brunt and being overworked. Personally, I think not being very good at pushing/skating switch has contributed greatly to my asymmetry over time. Think about it, front leg is like this strong, stable tree trunk that can balance you for days. Back leg is underdeveloped except for the calve which is monstrous from pushing, popping and controlling the board through balanced grinds and manuals. It's no wonder we get jacked up. Obviously I can't just get good at switch overnight, so I have been doing exercises very deliberately so that the muscles in the whole system relearn how to harmoniously support my weight.
The things that have done the most for me are bodyweight pistol squats, bodyweight Bulgarian split-squats, and standard weighted deadlifts and squats with dumbbells.
For the pistol squat you are going to be balancing on one leg and then descending into a deep knee bend. What I do is focus on the range of motion where I experience the pain and then stay there working that one zone. I'll take one or both hands and feel the quadricep working and see if I can find any soft spots where the muscle fibers aren't switching on, then try to get them activated so that I am conscious of the muscles controlling my weight. This helps instantly and after 30 seconds the pain is significantly less. I'll take a few moments mid session when I'm starting to notice pain and work the kinks out, which seems to make me way less sore afterwards. Also, they are good in general for your balance and stability on one leg. Pay attention to your foot and where it's contacting the ground. Are you heel/toe heavy? Is your arch collapsing in? Falling arches put your knees out of alignment and can carry upwards to lower back problems after years.
Just look up bulgarian split squats on youtube. The key difference between these and normal squats is that you can target the hamstring. You also get a nice stretch from the rear leg if you bend deeply. You can add weight to these, but it's not necessary to see the benefits.
Deads and squats are standard compound lifts, meaning they use a lot of different muscles. There is also wealth of videos on youtube about proper form and stuff, because you can really fuck yourself if you go about it like an idiot. These give you more of a glute workout than the other exercises, and having a powerful ass is important for athletic activity. I ordered a set of dumbbells that go up to 50 lbs each because I hate the gym and am poor, I suggest you do the same. In addition to supporting the knees and hips, these can help you increase your vertical and give your more pop. Plus you can get buff if you want.
Last thing, I hate to break it to you but yoga is dope. You don't have to convert to a hinduism or buddhism to reap these benefits. Yogic stretching reduces soreness, prevents injuries, and encourages circulation and healing. I also think there is something to the meditative quality that will benefit your skating mentally, but that's just my opinion. You can look up "yoga for __ pain" if you want to cut the fat. In my case, sun salutations, forward folds, pigeon pose, child's pose, warrior poses (there's a bunch of these), lunges, and downward dogs are all fundamental yoga poses target the legs and low back. Seriously, look into it with an open mind.
Obviously eating, sleeping, and hydrating are all important. Hiking uneven terrain is something that helps, too. I take joint supplements as well, because why not? Hope this all helps, maybe I'll try to write something more dedicated later. The most important thing is actually doing the work. It takes time, but not very much to see perceptible improvement. Last week I had a hard 4 hour park session with zero knee pain the next day, ZERO. That's a first for me since I was in my early 20's and I hope it wasn't a fluke. I've been working at this stuff for a couple of years, but much more consistently since quarantine, which I think is what has made the difference. Additionally, I think the final puzzle piece was when I realized that I could be doing a given movement while not actually using the muscles correctly. The body finds a way to compensate around its own weakness in the moment and then it becomes a habit, which must be broken.
Sorry for the length here, but I think its warranted. Our bodies are worth it, so I hope this helps someone out there. Even if you have different problems than me, this methodology can help you address what's happening, or not happening.