BENGALURU – Kim Clijsters’ tennis comeback in January has been pushed back as she recovers from a knee injury, the four-times Grand Slam champion said on Monday.Clijsters, 36, last played on the WTA tour in 2012 and had announced in September that she was planning to make a comeback when the new season begins in January.“I’ve had to make the decision that I will not be able to compete in January. I am undergoing rehab and treatment for a knee injury,” Clijsters said on Twitter.“It’s a setback but I’m determined as ever to get back to the game I love.”Clijsters’ decision to make a comeback will mark her second return to the sport after first retiring in 2007 to start a family.With 41 singles titles to her name, Clijsters hung up her racket after the 2012 U.S. Open and later worked as a tennis commentator.