At age 68, Justice Stephen Breyer is pretty spry, and by no means the oldest justice (John Paul Stevens takes that honor, at age 86.) So why was Breyer spotted walking with a cane Tuesday as he left the bench? A "flareup of tendonitis in his left ankle" is how Court spokeswoman Kathy Arberg explained it. But the injury was not suffered on the squash court or the bike trails of Cambridge. As we hear it, one recent day, as Breyer was walking down the hall in the Court building, he twisted his right foot as he turned to speak to someone. That caused him to put too much weight on his left foot, causing the flareup and necessitating the cane, which will be a temporary accessory. In the meantime, don't expect any major shifts to the left or right from Breyer.