How bad is parkour on the knee's

Even the stuff just on the ground can be horrible on the joints and longterm functionality of your body because there is still alot of impact.

There is a serious number of people out there in the Parkour world with knee joint problems just because training is not proper before hand. In parkour (just like everything else in life) its like people are on a race of some sort.. trying to get results in 20 mins or less.

Not going to happen. Parkour is not the place to want to rush to be the best.

Most people I see and meet now a days will have joint problems later on. What happens is soon your skill and what you can do metally becomes greater then what your body can do physically. Very dangerous point to get to. Its where personal constraint plays a big role in training in order to be safe. Even though you can do something, doesnt mean you should be doing it at all yet, and a focus on making it more and more of a safe reality should be the prime objective.

If you get any sort of knee pain, it means you are doing too much too soon. Wake up and realize you are only killing your body and you have to take a few steps back to take more steps in the future.

2-3 years isnt enough to do big drops unless you spent that time conditioning like crazy. Not even big drops though, most people should cut out most things out of their training and replace them all with conditioning.

Funny thing is, most people dont realize that with a proper body they would get BETTER at parkour FASTER! Why can gymnasts learn parkour faster, why can rockclimbers climb in parkour so easily, why do martial artists pick up fast... All because their previous training and conditioning allows them to. Conditioning is SOOO important. 99% of the time for someone under 3-4 years serious training its better off working conditioning then Parkour. With all the effort people put into making their precision jump 1 foot longer or catleap 2 feet higher they could make their body so much stronger. Muscle memory works wonders and even though you didnt train "Parkour things" your body will remember them and with a stronger body you will be able to enhance them all.

In the end you can tell your friend the amount of training he puts into his body that is not parkour will determine in the end how much Parkour and how long he will be able to do it.

I could have written this all in 1 sentence. Rush rush rush... You get hurt.