David Hasselhoff Sparks Health Concerns Using a Walker, But He's Fine

David Hasselhoff has fans worried after he was recently spotted using a walker and looking thinner than his beefy "Baywatch" prime ... but he is doing just fine, TMZ is told.

A source close to the Hoff tells us ... pictures of DH using the walker were of him leaving physical therapy ... which the poor guy needs after having both a knee and a hip replacement.

We're told he's still active ... exercising and hiking -- so fans can relax and stop spiraling with speculation.

The concern, of course, makes sense ... the beloved star is not snapped out and about much these days -- so when he is seen not looking exactly like he did in the '90s, fans are jarred. But, again, all is well.