He was born in Munich, the son of sculptor Joseph Knabl. He first practiced sculpture under his father's instruction, but became a genre painter as a pupil of Karl Theodor von Piloty. Of his genre paintings, his motifs usually involved the lower classes of society.
Paintings
German: Der bestohlene Geizhals, ("The robbed miser", 1874).
Die Schusterwerkstatt, ("The cobbler's workshop", 1875).
Die kleinen Zitherspieler ("The small zither player", 1878).
An Undiscovered Genius (1879).
Die Holzfahrt im bayrischen Hochgebirge ("The ride through the woods in the Bavarian mountains", 1883).