Noble Stella, a graded stakes winner in the U.S. and Canada, has been retired after suffering a knee chip during a workout at Woodbine."She was a very sound filly, but sometimes those things happen," said Roger Attfield, who trained the 5-year-old daughter of leading German stallion Monsun for Gary Tanaka.Noble Stella was in the midst of her best year yet. She had won this year's New York Breeders' Cup (gr. IIT) and Glens Falls (gr. IIIT) Handicaps in New York and the Bewitch Stakes (gr. IIIT) at Keeneland as well as placing in three graded turf stakes. Last year at Woodbine, she won the Dance Smartly Handicap (Can-IIIT) and Flaming Page Stakes. She placed in the latter event Sept. 24 in what was her last race.Bred in Germany by Gestut Etzean, Noble Stella was racing in Italy at the time Tanaka acquired her. Noble Stella retired with eight wins from 27 starts and earnings of $661,612. Her dam, Noble Pearl (by Dashing Blade), beat males in winning the Gran Criterium (It-I).Breeding plans remain undecided, according to Kern Thoroughbreds, which helps handle Tanaka's bloodstock.