(April 25, 2016, 2:13 PM EDT) -- ATLANTA — A doctor admitted that he had no expert opinion about why an implanted knee replacement system’s design was defective, the 11th Circuit U.S. Court of Appeals held April 20, affirming summary judgment to the system’s manufacturer on strict liability and negligence claims (Sandra Witt v. Stryker Corporation of Michigan and Howmedica Osteonics Corp., No. 15-12243, 11th Cir.; 2016 U.S. App. LEXIS 7145)....