NET
19 Like a bad tooth or a foot out of joint, so is confidence in an unfaithful person at the time of trouble.
Darby
19 A broken tooth, and a tottering foot, is confidence in an unfaithful [man] in the day of trouble.
KJV
19 Confidence in an unfaithful man in time of trouble [is like] a broken tooth, and a foot out of joint.