Casey Taylor: It's a fast pace, high intensity, exhausting job that Coach Beatrice Jirasek loves. Beatrice Jirasek: I've been coaching girls God you're talking 30 years. Casey Taylor: Arthritis in her knees nearly side-lined her for good. Beatrice Jirasek: I felt as almost if my body was going to collapse under me. Casey Taylor: When painkillers didn't work, she found the real problem, at her feet. Dr. Najja Shakoor: What we put on our feet has a huge impact on our knees and our hips. Casey Taylor: Doctors at Rush University Medical Center study footwear's impact on arthritis. Cameras, sensors and 3-D software measure the force different shoes put on your knees. They've looked at flip flops, clogs, flat sneakers and supportive shoes. Dr. Najja Shakoor: For years we've been thinking that really supportive shoes are good for our feet. Casey Taylor: The study found the opposite. Supportive shoes and clogs put 15 percent more force on the knees. More force equals more joint problems. Dr. Najja Shakoor: While the very light-weight shoes including flip-flops were associated with the lowest forces almost as if someone was barefoot. Casey Taylor: Rheumatologist Najia Shakoor won't prescribe flip-flops for everyone - but says wearing a flat, flexible shoe can ease the strain on arthritic knees and hips. Beatrice Jirasek: I was walking around with these clunky grandma shoes. Casey Taylor: Beatrice now sports new kicks and wears them at least six hours a day. Beatrice Jirasek: I'm thoroughly surprised that this shoe, which was like in the prototype and stuff, could have done that for me. Casey Taylor: It didn't eliminate the pain, but it helped, keeping this coach in the game. I am Casey Taylor reporting.