Sept 28 (Reuters) - Nick Kyrgios said on Tuesday he will undergo treatment to fix a painful knee that has been bothering him for two months and hopes to be fully fit for his home major at the Australian Open in January. The mercurial Australian, 26, headed home after playing the Laver Cup in Boston, his last event in the 2021 season. read more "Hey guys, over the last couple months, I haven"t been near 100% healthy," Kyrgios wrote on an Instagram story. "I"ve been dealing with left knee patella tendinopathy, and continuing to play without fully treating it can lead to further pain and greater set backs." Kyrgios, who reached a career-high ranking of 13 in 2016, has slipped down the ladder and is now ranked 96th in the world after playing very few tournaments in the last two years during the COVID-19 pandemic. He remains a fan-favourite with his shot-making wizardry and is among the few players in the world to beat the Big Three of Roger Federer, Rafa Nadal and Novak Djokovic. Kyrgios had pulled out of a highly-anticipated first-round match against Britain"s Andy Murray at the Winston-Salem Open due to knee pain in the leadup to the U.S. Open but was fit to play the major and the Laver Cup subsequently. "I"ve chosen to fly back to Australia to reassess and am planning to get PRP treatment to settle down and rehab my knee," he added. "I"m disappointed it has kept me from playing my best tennis and hopefully with everything going smoothly I will be back to 100% by the Australian Open."