Trials: knee and elbow hurting, am I doing it wrong?
This should be really asked to you physicist, not bicycle related forum.

If you are new to this, this can be "normal", as your bones and ligaments are not used to constant shocks. Do not ignore the pain. Take more time off, if needed.

This is typical problem for runners without previous experience. You can not just start running half-martahons without knee pains which can later lead you to meniscus surgery. You need to start slow and use 10% rule (increase your distance/time per week by no more than 10%).