I'm 53 yr old having diabetes, thyroid, BP and knee pain. Should undergo tkr or not?

TKA. Pain not responding to conservative treatment, along with deformity, is the prime reason to have tka. Tune up the dm, htn, & thyroid disease with pcp prior.
Preoperative risks. Are present but don't necessarily preclude tkr. Talk with your physician to make sure you don't need a preop stress test.