Sometimes you get sore joints as you’re growing up, which can be totally natural and is often due to growth spurts as your joints try to accommodate the changes in your muscles and bones. Your joints will not fully stabilise until you are an adult.
Joint problems typically happen when the joint is subjected to repetitive strain, such as you might get in your thumb or wrist joint if holding a computer controller for extended period of time 😉 The way to resolve this is to ocassionally put down the e.g. controller, and relax your wrists and then strtch them in different planes of motion.
Different sports have different cool-down approaches, depending on the muscles and joints that are worked most often.
On a long term basis, the safest way to ensure the stability of your joints is to engage as many muscles as possible when performing tasks, so that the loads on any one joint are dissipated. This is also partly refers to as using your ‘core muscles’, and is a type of exercise that things such as yoga and pilates is good for. These techniques aim to exercise the whole body at the same time; exercises that work a single part of the body in isolation are what can lead to joint problems because whilst you may be able to lift a weight with one part of your body, such as your arm, there is no guarantee that you back can support that weight, unless you have trained you arm and back together.
There are several genetic conditions that can be inherited – although there is no guarantee you will get them – such as arthritis (where your own immune system starts attacking the cells of your joints). Arguably, you can go some way towards lessening your chance of developing arthritis by not overly damaging your joints by incorrect exercise, and also by eating a balanced healthy diet with a good range of omega oils and not being overweight. You can read more about this here: http://www.arthritis.org/preventing-arthritis.php