Sharp severe pain in left knee. pain occurs when bending or lifting leg, when going down stairs, and when pressing quad-edge of kneecap.

Knee: An easy test for arthritis is put hand on kneecap when bending and straightening the leg. If u feel a grinding called crepitus indicates some arthritis. There are conservative treatments in such a situation

Protection!: You know the joke "Doc, it hurts when I do this." and Doc says "Don't do that! Well, for now try not to do those things. Also use a good knee brace to protect/imobolize the knee until you can see a doctor for an exam. Rest will help whatever it is to stop further irritation damage. Knees can be unforgiving, so treat them w/ gentle care. Best!