Fig 3.

(A) With the patient supine and left knee slightly flexed, the full-thickness lesion in the femoral trochlea is exposed (arrow) through a medial parapatellar arthrotomy. (B) The borders of the lesion (arrow) are sharply delineated using a 15-blade scalpel. (C) A ring curette is used to debride the base of the defect and create stable vertical edges at the periphery of the lesion (arrow). It is important to remove the underlying calcified cartilage layer without penetrating the subchondral bone. (D) A 2.7-mm drill is used to perforate the lesion and gain access to the underlying bone defect (arrow). The sclerotic margins of the defect are debrided with a curette and drilled with a k-wire.