In dogs, forelimb lameness is almost always caused by pain. limping means placing less force on a painful limb. This dog is lame on his left forelimb. The easiest way to spot the limp is to look for a head nod. He lifts his head when he uses his painful left leg. His head nods when he places his sound right leg. This feature coined the expression "nodding on the sound limb". If both forelimbs are painful, a head nod can disappear or shift from side-to-side.
