When a dancer loses the use of her legs, is she still a dancer? That's the question implicitly asked and answered by Nancy Buirski's lithe documentary Afternoon of a Faun: Tanaquil Le Clercq. Long-legged wonder ballerina Le Clercq was the star of the New York City Ballet through most of the 1950s, until she was stricken with polio during the company's 1956 European tour, never to dance or walk again. Known to her fans and close friends alike as Tanny, Le Clercq was the kind of performer whose humor and mischievous spirit shone through in her dancing. According to lore, balletmaster George Balanchine first met her when she was a student at the School of American Ballet, a scowling mite standing in a hall with her arms folded across her chest. "Why aren't you in class?" he asked. "Kicked out," she replied crossly. Years later, Balanchine would marry Le Clercq -- his fourth and final wife -- though she also won the heart of Jerome Robbins, who, in 1953, created an eerie, breathtaking dance just for her, choreographed to Debussy's Afternoon of a Faun. Buirski blends clips of Le Clercq's magnificent, tensile performances with interviews with those who knew her. But if polio ended Le Clercq's run as a dancer, Buirski clearly shows that the spark that made her great couldn't be snuffed out so easily. Even in a wheelchair, Le Clercq, who died in 2000 at age 71, commands authority with little more than her captivating, wicked smile. But then, being a dancer is dependent on knowing which muscles to use, and which are most important.