Thanks for the query to H.C.M. Forum.
Bump below patella
(knee cap ) may be an outgrowth from tibia
While you mentioned in your query that pain is in both knee joints , so simultaneously involvement of both joints are due to , Osteoarthritis
, rheumatoid arthritis
Get in blood for R A factor, C B C, uric acid ( gout , very high level), E S R (if very high suggestive of osteoarthritis or tubercular arthritis
X ray knee is very important for bump's growth.
Consult an Orthopaedician and get his opinion.
Physical examination is very important in this case.