The Billikens remained unbeaten in the Atlantic-10 Conference.
St. Louis allowed the Hawks to shoot just 31 percent from the field. St. Joseph's made 1-of-16 from 3-point range and turned the ball over 16 times.
Loe made 4-of-7 from the field and hit all six of his tries from the foul line. Jordair Jett was the only other St. Louis player in double figures with 10 points to go with his seven assists.
It was the 15th straight victory for St. Louis (21-2), which has lost this season to Wisconsin and second-ranked Wichita State. Eight of the Billikens' victories have come in Atlantic-10 play.
Ronald Roberts led St. Joseph's (15-7, 5-3 A-10) with 19 points.