Clasically, if you have problems with stairs in theface of no significant finding on MRI,
You may very well have simple overuse syndrome- can be called "jumper's knee" or "runner's knee, even if you don't do much jumping or running!!!
It sounds to me like Patellofemoral Syndrome.
This can be easily checkd by you, because most people with this:
1) have flat feet or arches that fall when they stand
2) crunching under the patella when you move
3) Significant pain with stairs as you do
4) and my favorite: Look at the sole of your shoes, and if your shoes show a lt of wearing out of the outer aspect of the sole (at the heel) this is easy to figure out!!!
Here is a site on this problem:
5 tings help this problem:
1) antiinflammatory meds (ibuprofen 600 3x a day)
2) soft arch supports in your shoes (Spenco is the best and can be found at any foot locker)
3) Stretching and strengthening exercises-
4) Taping of the knee called McConnell taping
5) A knee stability sleeve, with the circle cutout over the patella.
If all of this fails, you can have other ortho surgery to stabilize the knee and patella- but you don't want this unless necessary. If your shoes are worn like I escribed, you can purchase sneakers with "pronation control" at any specialty shoe store- Foot Locker, Lady's Foor Locker, etc.
This problem, like arthritis will worsen with cold, damp weather.
But- if your MRI does not show significantfindings- I have sometimes requested a "sunrise" xray of the knees. Chec in with your doc- there are definitely other possibilities such as this VERY common problem.
I hope this was helpful!!!
Good luck, and be good to your knees! I will be happy to answer anything else you need about this.