Knobbly means covered in small hard lumps. Knobbly knees, a knobbly stick, knobbly potatoes.
It is affectionate rather than critical, which is why knobbly knees is a joke rather than an insult. Americans spell it knobby and use it the same way.
1adjectiveknobblyCovered in small hard lumps.
“He walked with a knobbly stick cut from the hedge.”
knobbly is a texture.
From knobble + -y.
Etymology from Wiktionary, CC BY-SA