Step 4: Read and complete the decision guide to learn more about your symptoms.
From your answers (age greater than 45, other joints are bothering you, the painful knee is swollen, but not locking or giving way), a number of possible conditions could be causing your knee pain, including:
rheumatoid arthritis or a related condition (such as spondyloarthropathy)
crystal-induced arthritis such as gout or pseudogout
some combination of these.