Step 4: Read and complete the decision guide to learn more about your symptoms.
Based on your answers that you are older than 45, other joints are bothering you, your painful knee is swollen and there is locking and/or giving way of the knee, there are a number of possible causes of knee pain. More than one may be present at the same time, including:
rheumatoid arthritis or a related condition (such as spondyloarthropathy)
cartilage damage (may also be called a torn meniscus
ligament injury, including anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) injury
crystal-induced disease such as gout and pseudogout.