|New runners should take care of their knees & ankles|
There is a chance this might have been an excuse for a newbie runner to step back from the aspirations of becoming a regular runner. Of course it could be a sensible thing to do for some people, for others it is a natural part of becoming a runner and persevering is the route to take.
Here's a few thoughts on this:
Making sure a new runner has the right shoes is very important. When I was getting into running I almost quit because of this very issue; but thankfully I found having a gait analysis and some proper shoes solved the problem for me. I haven't looked back since. One more thing, make sure you have some proper running socks too (don't be a cheap skate and buy some cheap, naff "sport" socks).
Take it easy
Don't over do it. It can take several months to condition your body to become a regular runner. Just think about your body, especially waist downwards. All of the joints take a pounding when you start to run, your body is doing something new and it needs time to adjust. Your joints, ligaments, tendons and muscles all need to become used to running and it takes time, build up slowly, gradually and consistently.
If you run on a hard surface, you will be subjecting your body to maximum pounding. The absolute hardest surface is concrete; those rock hard paving slaps. These paving slabs are bad news for the runner as apart from being rock-hard, they are often cracked and uneven which can easily lead to trips.
If you can run on a softer surface such as grass or dirt tracks this might help. For some it might even be worth getting in the car, or on your bicycle and going somewhere better for running.
Avoid running down any hills, this will simply makes things much worse. Hills will come later as you become a more experienced runner and you'll come to like them but for now they are best avoided if you can. If you must include hills because of where you live, you could try walking down them or taking it very, very slowly.
Do you run awkwardly? Have you had previous injuries? Perhaps your legs or feet are particularly uneven in some way? You might need to see a Podiatrist as this is a specialist area and you may need some expert advice.
Make sure your diet is good. The nutritional needs of a regular runner are, arguably, little different to that of a normal, healthy diet. What defines a "normal, healthy diet" is, of course, open to debate!
Nevertheless regular runners need to ensure they get adequate carbohydrates for the energy needed in running (but don't over do this is you are trying to lose weight!). More importantly I believe runners need protein in it's various forms (although I am a vegetarian) and antioxidants for repairing the wear and tear. It would be easy to talk endlessly here about nutrition but let me leave it there for now.
This naturally follows the previous mention of food. Regular runners are unlikely to have any problems sleeping but it is important to make sure you get all the deep sleep your mind and body requires. Amongst other things, this is where your body will be repairing itself and making itself a little bit stronger each time. Please, please please, do not underestimate the value of this.
Many people start running to lose some weight (that was me a few years ago) and it's a fantastic thing to do. However when you run, it is said that 2 or 3 times your body weight lands on each foot, with each footstep. So if you're 3 stone over weight, just think of that weight landing on your feet each step. That's quite something to handle, step after step.