Here's tennis star Juan Martin del Potro showing us how he's recovering from that pesky knee injury ... a Miami beach romp with his model girlfriend!
Feelin' better already?!
Juan -- the former #3 ranked player in the world -- fractured his kneecap earlier this year after slipping on grass during a tourney and had to undergo surgery to repair it.
He's hoping for a big-time comeback when he's all healed up -- but in the meantime, the 31-year-old Argentinian stud is relaxing in Miami with actress/model Sofia Jujuy Jimenez.
They reportedly started dating earlier this year -- and it seems to be going REALLY well .