I run about the same as the parent, give or take, and mine are fine. I've done a few ultra marathons and I'm gearing up for one in September where I'll be traversing 170mi for a week while carrying 8-10kgs of weight(www.g2gultra.com, for the curious). For what it's worth, I'm 32, and have done a number of ultras since I started running actively at 25. It takes time to build up.

One observation is that if you were running everyday(I'll assume you mean that literally), then you weren't giving yourself time to rest and recover, which may be why you are experiencing your pain. I hope you recover soon!

Having said that though, if you are experiencing knee pain(and I can say I've had my share), you're doing the right thing by resting and taking up swimming. I'm not much of a swimmer at all, but getting in the pool and being able to work out despite having hurt myself felt like heaven.