<s>[INST] I have knee osteoarthritis in left knee for last 4 years and I m taking treatment for it but for last one month my right knee gradually begins to swell and pain.I did icing and elevation for reducing swelling but could not succed much.my question is -what factors and reasons may be responsible for this swelling and pain and what lab tests should be done. [/INST] Hello and welcome to ChatDoctorSwelling and Pain is the common problems faced by the patient of osteoarthritis involving any joint. Swelling is due to the exaggeration of the process of normal synovial fluid formation in the joint. Normally a small amount of fluid is present in OA patient in can reach above 100 ml this causes distension of joint capsule causing pain in addition to the preexisting pain. There is immediate relief of pain.lab test required are-Plain X-ray both knee joint- anteroposterior view full weight-bearing and lateral view with 30 degrees of flexion. Only after seeing the x-ray and physical examination can the joint condition be assessed and further test prescribed. There can also be co-existing It D deficiency and Osteoporosis or Osteomalacia which can cause pain in OA patient. These diseases would also be apparent on X-ray and accordingly blood test for It D, calcium be prescribed. My recommendation is to visit Orthopedic surgeon to Chat Doctor.  </s>