What Are The Symptoms Of Rheumatoid Arthritis?

hello sir my mother is 42 years old.she is having pain in her knees from the last one week especially in evening.we consulted a doctor and he prescribed some tests.the report has come.it is wriiten in the report that crp is negative,rheumatoid arthritis factor is non-reactive and a.s.l.o. titre is negative.please tell that what does this mean and has my mother arthritis?