Pork knuckle is the traditional name in United Kingdom. Elsewhere, butchers sell the same piece — or a close cousin — under a different name.
Same anatomical primal — jambonneau is the cured/cooked French version of the pork knuckle/hock. Different from German Schweinshaxe (roasted with crackling skin) and from fresh-jarret stew preparations.
Same anatomical cut (the lower-leg/hock joint). Schweinshaxe is specifically the Bavarian roasted preparation with crackling skin; the generic 'pork knuckle' covers boiled, cured, smoked, and pickled preparations across other traditions.