Hi, thanks for writing to HCM. The description suggests that you are an elderly person with osteoarthritis
of the joints. Your swelling of the right knee could be due to a "medial meniscal cyst" which will be painful and appears on medial side of knee. It usually occurs in degenerated knees. Joint effusion
also occurs commonly in osteoarthritic knees, but the swelling will be diffuse in nature distributed across the whole joint.
There is no way that you can treat this condition by yourself. So I advise you to consult an orthopedic surgeon and follow his advise accordingly.
Hope this helps