Metta World Peace said he’s already feeling the good effects from the platelet-rich plasma (PRP) blood-spinning procedure he underwent on his knees Monday. World Peace, who has played just two games since Dec. 21 because of an arthritic left knee, said he plans to return to the Knicks lineup in two weeks. Each injection took 30 seconds, and World Peace said he decided to have both knees done. “It felt pretty good,’’ he said before the Knicks’ 89-85 win over the Pistons Tuesday night at the Garden. “It was weird. It was weird. I was like ‘Wow.’ When I was walking home I said, ‘Wow, it’s kind of cool.’ But I don’t want to test it yet. “I did both knees because I didn’t want to be off-balance. And I know it’s going to be help me a bit. I didn’t want to be off-balance and hurt my other knee.” The former Ron Artest had the procedure done in Manhattan, though many athletes fly to Germany. But he found a New York doctor who is partners with a German blood-spinning specialist. PRP is injected into the knees to promote faster healing. World Peace said he has had his knee drained six times since training camp started.