The league convert says he needs up to two months' rest on the joint to avoid reconstructive surgery.
"I'm pretty devastated to be ruled out - I'd earmarked the tour to really make a claim," the exciting Cardiff Blues player said. "I've got severe bruising in the shin and quad bones, and I've also got a tear in the posterior cruciate ligament."
Harris is the latest in a growing list of players who have been ruled out of the tour as new coach Mike Ruddock looks to start his reign with victory abroad. Apart from last year's World Cup, Wales have not won away from home since a tour of Japan nearly two years ago.
Scarlets hooker Robin McBryde is out with a shoulder injury and regional team-mate Dafydd Jones has a similar injury. Lock Rob Sidoli and scrum-half Gareth Cooper are in doubt and fullback Kevin Morgan has ruled himself out.
"It's been an extremely long year with the World Cup - we've been playing international rugby since July last year," Harris added. "There's only so much a body can take at that level and over the next two or three weeks you'll see plenty of players dropping out of tours - not just for Wales but for every country that's going on a tour."