The 24-year-old baller went under the knife last week after going down with the injury against the Warriors on April 12 ... and he appears to be in great spirits as he kickstarts the recovery process.

Murray showed off some post-op pics on Tuesday ... captioning them with a positive note -- "Brand new."

Of course, the injury happened in the final minutes of Denver's loss to Golden State ... when Murray's leg buckled after he drove to the basket.

The scene was tough to watch -- even for the broadcasters, who were audibly emotional over the injury.

But, Murray will recover and get back to the court ... just with a new-look knee next time around.

Sports stars like Odell Beckham and Joe Burrow have showed off their ACL surgery scars in recent months ... and it's safe to say Murray's is the least gnarly, so that's a plus for the hooper!!

It's always bad to see any athlete go down, but it was especially tough to see Murray get hurt -- the guy has been tearing up the league over the past 2 years.