Drink tons of milk

Stretch and do some squats.

what they said, and:
Take warm baths every day until it feels better. (I do this anyway because my back is awful.)

As for what's causing it, it might have something to do with your playstyle, which can always be adjusted. I've never had knee pain from DDR before, but I can only assume you lower your body a little bit to do runs which might be the cause. Or if you play no bar maybe that will happen, I don't do it enough to know.

Other than that, definitely stretch before you play, take some ibuprofen if needed, and if it gets really bad see a doctor lol.

Playing no bar flat footed actually isn't that good for you at all. So when you do play no bar mix in a little toe work into it. That's what I do.

I've played flat foot no bar for years now and have only had occasional small joint pains. The best solution is to just lay off the exercise for about 1 week, minimum. You've been doing trampolines, ITG and God only knows what else, give your legs (and body) a short break. Exercise is the process of breaking down your muscles, you have to make sure you allow them to recuperate appropriately.

If your joints continue to hurt, even after a week long break, try seeing a doctor or Physical Therapist if you have the insurance to cover it. A co-worker of mine suggested Omega 3 vitamins to help alleviate joint pain. I haven't tried it yet, but it's supposed to help.

Oh yeah, and although it's been said already, make certain to thoroughly stretch your legs before any session. I had broken this habit over the last 6 months or so, but lately I've been doing it again, and it makes a HUGE difference in my scores and how my legs feel afterwords.

I tore my knee cartilage and needed to have surgery. Of course, I'm not sure how much ddr contributed to that compared to other impact sports *cough gymnastics / track*

You should probably try to pinpoint what area of your knee actually hurts, because that will probably be a good indicator of how serious it may or may not be and what you would need to do to make it go away.

I'm gonna have to agree with Ethan though, if you have health insurance there is absolutely no reason you should not see a doctor, especially if it gets worse, even if only a little bit; if something gets worse over time instead of better that's usually the sign to ask for outside help.

One possible contributor to joint pain is weakness in the parts that support your knee.  Stretching and weight lifting focused on the thighs has been noted... somewhere online... to help prevent knee strain; I can corroborate in that 11's on ITG were debilitating for me a few months (approx. 6-9 months ago) even though 12's and 13's had been fine for me 2 years ago until I started training the various muscles around my knee at the gym (both sides my family has a history of knee problems and I was about to just stop with dance games figuring I'd done too much, but then my knee started holding up to 12's again in only a few weeks).  Basically, your knee exists (partly) to pick up the slack for the rest of your leg and suffers for it if you constantly expose yourself to such strain.

As for the bar debate - I have a feeling no bar is healthier since it places you in a more natural position.  Furthermore, balance-focused activities are good muscular exercise for your legs and the lower 2/3rds of your torso, which overlaps with the above leg training.

Let me clarify what I mean by flat foot being bad.

I've seen kids play flat foot and BARELY bend their knees. Over a long period of time. That will kill your joints. So remember. BEND YOUR KNEES.

yeah and ur mind lol

man up

Ironic coming from you. She/he thing.

Best advice so far. =p  I'll let my cartilage know that its possible deterioration is too female for my liking, and continue trying to pass retarded ITG stamina songs.

discovolante - I do take warm baths and showers, which are lovely.  I do actually sink lower on the bar when going into tough runs, so I think I do need to mess around with my playing style.

All the other suggestions are great too, and have been corroborated by my internet research.  I need to get better shoes, I need to do longer warm ups, and I need to stretch.  My leg muscles are pretty strong between yoga and the new addition of trampolines, so I'm not too worried about that.  And I certainly know how to stretch the muscles I need.

I do play flat foot with really bad sneakers, and I'm bad at bending my knees sometimes, so I'll work on both of those things.

Glad to know I'm not the only one with this issue, though!

yeah... cing how im tricksy this thread is for those clown posters only :-)

Wow, I completely forgot to mention this. I used to play in Vans shoes all the time. I loved them for various reasons, but since switching to my NewBalance 992s, I have noticed a significant decrease in in joint pains and a slight increase in my performance. Shoes specifically designed for running are built with impact resistance in mind. So when shopping for a new shoe, I suggest looking in that direction. I always try to sell people on NB because I've been so thoroughly impressed with them.

I played DDR a bunch since I was 6 and now I have leg pain all the time. I guess I did it wrong, haha.

I used to do that ALL THE TIME when I was starting ITG, and it took a huge toll not only on my knees but on my upper arms and back. Just get in the habit of not doing it as soon as you can. Standing with your torso straight is key not only to timing but to healthy posture.

Eat more protein and calcium...