A drill guide assembly for accurate and stable drilling of a bone tunnel. The drill guide assembly includes a guide body having first and second ends, and a slot extending from the first end toward the second end. The drill guide assembly also includes a curved guide arm having a first arm connected at an angle to a second arm. The first arm terminates in a distal tip. The second arm has first and second sides, and is slidable within the slot of the guide body. The second arm also includes detents along its second side. A locking mechanism is attached at the first end of the guide body and in a first position, and the locking mechanism is engaged with one of the detents. The drill guide assembly also includes a clamp mechanism attached at the second end of the guide body and a guide sleeve removably extending therethrough.