Running everyday is probably not good for your knee joints and may lead to OA but... up to you
Regular stress is causing things to get stronger.
Running every day can be not good for the knees, if you increase the volume too quickly without giving the joints and tendons necessary time to strengthen up, if you suddenly introduce too much stress (try to sprint when you have never done it before), if you don't sleep well or give time for them to recover, if you have bad diet or if you are sick for some reason and your body has impaired ability to recover.
It can decompose for example muscle and other connective tissue (which actually is quite important to be healthy), but it does limit ability to build tissue.
Lesson from bodybuilding crowd is that you need to eat protein with every meal if you are serious about building anything. They want to build muscle but it really extends to all tissues of our body.
I have nothing against veganism and vegetarianism. It is a lofty goal.
But strictly on health standpoint, no amount or kind of plant food can (currently) beat healthy whole animal tissue (you should really eat more than just meat and also not all animals are same way healthy to eat).
Now, this doesn't mean there can't be better plant-derived foods in the future. A protein is a protein is a protein.
The problem with plant based protein is they come in wrong concentrations, wrong combinations, they are missing some stuff or they have extra things that make protein more difficult to absorb. If we can fix these points, we can have healthy plant based diets.
But really the main benefit of meat is that you get close to the right concentrations of everything by very definition. If you eat whole animal, that is. We have evolved to eat meat and only evolved to eat plants to supplement some small things (mainly vitamin C and to eat fructose and alcohol to get fat for the winter).
With this, any stupid person can eat relatively healthy diet. You just put a steak in your mouth and you are 80% of the way there.
On the other hand eating healthy diet on plants is a difficult task requiring planning and diligence that I think half of the population is simply not equipped with brain power to execute correctly.
We evolved as opportunists and generalists. Humans are capable of taking nutrition from plants or animals.
> and only evolved to eat plants to supplement some small things
I believe this is backwards. There are examples of hunter-gatherer societies with meat-dominant diets, but more typically hunter-gatherer diets were/are predominantly plant-based. In most environments hunting was a less reliable source of food and more opportunistic.
> But really the main benefit of meat is that you get close to the right concentrations of everything by very definition.
Not really. Maybe if you were eating chimp... but chickens have very different compositions to cows, pigs, salmon or polar bears.
> You just put a steak in your mouth and you are 80% of the way there.
It really isn't that simple. For example, it is well established that excessive red meat consumption raises the risk of colorectal cancer and other bad things.
Well yes but no. Large brains were largely made possible by the fact we mastered fire (mostly to cook meat). Look at gorillas, they eat plants and spend most of their waking life to forage for food. Having even larger brains means that foraging would be impossible to sustain a modern human's constitution.
I keep having small injuries here and there. The difference is that I am currently running 70km a week on average (7-10km on most week days, 10-21.1km on Sundays). My leg muscles are hard as rocks and my Achilles tendons are twice as tough as before (based on the increased cross section based on the images I have). It is much harder to evaluate load capacity of my knees (I don't have images to compare) but it is easy to see If I just started running 10k every day (even if I was able to do it aerobically) I would probably blow my knees in less than a month.
Additionally, I suffer from torn ACL and before I started running my knee was kinda lose which made even walking a bit difficult (constant popping sounds, pains, etc.) Thanks to running and strength training the stronger muscles and other tendons took the slack off my knee and I pretty much forgot that there is anything wrong with it. I just need to pay attention to not get carried off too much and start doing some stupid shit like playing soccer or basketball which would definitely be a bad idea. As long as my activity has controlled moves like running or hiking in not too difficult terrain, I am fine.
Is that universally true? Not every system in our body is so anti-fragile.
I walk a lot, but whenever I tried running, I had immediate problems with both joints and inflamed muscle. My guess is "too many hard surfaces". We are definitely not naturally adapted to pavements and asphalt.
But training in an uneven terrain will, over time, strengthen your other muscles and tendons that do not get much workout on pavement. It is important to understand if you want to move to running in uneven terrain you have to reduce your volume initially, pretty considerably, to give time to adjust.
As to your problems with inflamed muscles and joints -- I have some experience with this I can share.
First is that your aerobic capacity develops much faster than your joints and tendons, especially if you are older. It takes years of regular running to get your joints and tendons to be able to accept daily high mileage running.
There is no other way than to start small (say 1-2 miles every other day) and slowly, slowly build it up and react every time you have any problems (by stalling your build up to get time to catch up).
Connective tissue reacts best to high, non-repetitive loading. The fastest way to improve your tendons and knees is to start lifting heavy shit. That's why all pro runners are also going to the gym to lift weights. Not because they want to build muscle (you don't want muscle especially in legs because you need to move that mass back and forth) but because it strengthens joints and tendons and makes your legs more resilient to stress. Also, stronger core muscles help maintain good posture throughout long run preventing injuries.
Personally, I found walking is an excellent supplement to running. Walking long distances regularly will also strengthen things with less chance for an acute injury. I have even started walking with a loaded backpack (read up on rucking).
I've been running every single day no exceptions for almost 8 years, including marathons and a half marathon at least once a year. Most of my runs are slow, all of them are run with small steps and fore/mid foot strike.
Stomping around the track huffing and puffing is not the way to do it, but when done right it is absolutely wonderful for the body.
Running properly is part of the way to avoid injury.
I had 3 knee surgeries over the years and have arthritis in that knee and actually running with OA seems to be an ok thing to do, which seems to correlate with my experience that my knee pain is less when I run than when I don't.
As usual, there's lots of nuance and it depends on the person and the situation!
Joints are not something you can recover easily once they are damaged.