Before the pandemic slowed medical services to a crawl and limited it to necessary procedures only, the VA did full body imaging to assess my injuries after having been hit by cars twice in less than 20 years (2001, 2018), with various chronic aches and mobility issues.
My back, neck and shoulder were a mess, but, luckily for me, my hips, knees and ankles were fine, remarkably good for a 60+ y/o guy with a history of indulging in reckless sports in addition to a penchant for being hit by errant drivers. All my serious injuries were above the waistline. Brain scans showed nothing, which explains the echoes and rattling around I was experiencing upstairs.
So now whenever my hips, knees, ankles or feet hurt, I know it's soft tissue stuff. I just need to rest or at least ease up off the effort, and do my physical therapy stuff. I tend to neglect the recommended stuff like foam rollers, using my percussion massagers, manual kneading and making dough out of muscles I can reach with my hands, etc. And the usual stretching and strengthening stuff to build up and maintain the core, leg stability and balance, etc.
Like many active folks who still think they're teenagers or 20something at heart and in their minds, I tend to just want to jump on the bike and ride, or pull on my shoes and run. And I can get away with that just often enough to encourage bad habits. But it'll catch up with me and I'll have issues like the persistent aches in my left hip and lower back, radiating down past my left knee. And it's just sore muscles and soft tissue stuff. As soon as I rest or do easy active recovery, use my percussion massagers, TENS unit (TENS and EMS devices are terrific for therapy on muscles we can't easily reach with our hands, especially if we don't have the luxury of a masseuse), soaks in a hot bath with Epsom salts, etc.
My occasional knee twinges always turn out to be referred pain from tight, achy quads, hamstrings, calf muscles, etc. If I take a rest and active recovery day to just do the physical therapy stuff, it'll feel fine in a day or three.
But if I keep pushing despite the pain, my form and posture degrade and I risk worse injuries by cycling or running lopsided, pushing harder with one leg to compensate for the other, etc. And that can eventually lead to joint damage.
Since the pandemic started in 2020 and I did mostly solo rides and workouts rather than group rides with friends, I had more time to fill. So I watched a ton of YouTube videos on physical therapy, fitness, conditioning, etc., related specifically to cyclists and runners. There are too many junk videos out there, or some from well meaning physical therapists and coaches who know what they're talking about, but can't seem to condense 30 minutes of rambling anecdotes down to a 3-5 minute video... pretty much like how I write posts online.
But some are very good and helped me reinforce better training habits to avoid injury and encourage patience. I have a bad habit of pushing too hard every workout. Cutting back on the fast competitive group rides helped me work on my own fitness and technique, appropriate for my age rather than trying desperately to keep up with guys and gals in their 20s-40s.