Avoiding Knee Pain

I think having knee injuries is like a proof that you are doing your best in cycling. It is also good that you tried some adjustments in your bike to prevent further injuries.
That's an interesting notion but having knee injuries is like a proof that you are 'not' doing good in cycling. Well, the real cyclist rarely experience the knee pain because they are fit.
I'm not sure that a persons fitness as got anything to do with pain and injury in a joint such as the knee. The fittest people on the planet can still pick up knocks and sprains, so figuring out what the pain actually is, is the way to go before you can start to treat it.
Before diagnosing you knee pain, you need to know what's the exact cause of the knee pain. Is it because of some chronic disease like arthritis? Is it temporary general knee pain?
You can't actually explain the cause of the knee pain. Most of the knee pains just the general pain and you don't need to think about it. Most people don't do the regular checkups. It is very necessary to do the regular checkups to find out that the disease is because of some diseases like arthritis.
Yeah, you're right, you should adjust the seat to avoid some muscles pain. Our body should be comfortable in a bike, specially for a long travel. Sometimes the sits looks good and comfortable but you will just notice that there're something wrong after the long travel using your bike.
I've struggled with knee pain for quite a long time myself, so I can emphasize with you when it comes to this issue. There are mainly two things that have helped me when it comes to remedying knee pain while biking.

The first is, as you mentioned, to adjust the seat height. Depending on the height of your seat, the angle at which your legs have to pedal changes the amount of pressure you put on your knees. Experiment with different heights to see what works for you.

Another crucial element is to buy a multi-speed bike if you don't own one already. The effort it takes to pedal on a single-speed bike can sometimes be too much for some people, so being able to adjust the gear depending on the incline of the road can make things a lot easier for your knees
Pardon me for asking if you have gout or arthritis. My elder brother had severe arthritis that greatly bothered his joints. His hands and knees were painful. When it started, the pain was felt when he exerted effort like riding a horse. He was a horse jockey by profession. And he thought the pain was due to his riding.