The 49ers said after practice was over that McKinnon will be having an MRI to assess any damage.
Matt Maiocco of NBC Sports Bay Area reports McKinnon grabbed the back of his knee while hobbling after a run early in the practice. McKinnon was not contacted during the play.
Washington running back Derrius Guice was diagnosed with a torn ACL after an MRI on Friday. Guice was injured in Thursday night’s game and, like McKinnon, said he felt well in the immediate aftermath of the injury.