the knuckle is larger than my actual finger  I have the same issue.  My wedding ring is a size 5.75 (UK size L) because that's the size of my knuckle, but my finger itself is a size 5.25 (UK size K).  I'm not a petite person (5'9" and 130 lbs / 1.75 m and 59 kg), but my ring will not stay put on my finger; it slides down and sits on my knuckle.