Knee Started Hurting, Tendon In Back Is Larger And Pain Getting Worse. Have Arthritis In Finger Joints. Suggest?

My left knee started hurting a little bit a couple weeks ago and the pain came and went over about a two-week period. I noticed that the tendon in back seemed larger than my other knee when I straightened my legs, but no pain when I pushed it. Now the pain is constant and getting worse daily. I hadn't done anything that I could recall to injure it. I don't run or do aerobics. I am almost 62 years old (female), in good health as far as I know (no insurance so I never go to the doctor). I am 5'1" almost, and weigh 110 lbs. I have arthritis in a few finger joints and symptoms of rheumatism that are unbearable in the mornings...fading away later. This all seemed to come on me in the last year or so, but the knee pain has progressed daily and I can barely stand it. I want to go to the emergency hospital tomorrow, but if it's arthritis I am wondering if it would just be a waste of time. It feels like my knee is swelling inside (my lower back pain is bad along with it..hmm) but on the outside it doesn't look swollen. I cannot bend it or straighten it. I guess it doesn't really matter what it is because I cannot afford the care beyond aspirin or naproxin. So, how do you treat the untreatable? ha!