World slalom champion Frank Woerndl of West Germany will undergo arthroscopic surgery next week to repair cartilage damage in his left knee and will miss three weeks of competition, his doctor said Friday.

Woerndl, 29, is expected to recover in time for the World Alpine Skiing Championships in Vail, Colorado, doctor Ernst-Otto Muench said. The world championships are scheduled for Jan. 29-Feb. 12.