As Tom Selleck approaches his 80th birthday on January ... Selleck has been struggling with weight gain, joint pain, and the recent end of his long-running TV show Blue Bloods.

Tom Selleck is undergoing physical therapy ... "What he really needs to do is lose weight because all those extra pounds aren't doing his joints any good." A separate source told Closer in ...

Tom Selleck is undergoing physical therapy ... "What he really needs to do is lose weight because all those extra pounds aren't doing his joints any good." A separate source told Closer in July that ...