Continuous instability and repetitive pivoting in chronic anterior cruciate ligament (ACL) deficient knees results in impingement of the tibial eminence on the femoral condyles and a shearing effect which gradually damages articular cartilage.The high incidence of large chondral defects of the medial femoral condyle associated with chronic complete ACL tears is widely known and requires treatment, which is difficult and controversial. In most cases the torn meniscus is repaired and ACL reconstructed but the chondral lesion is usually ignored.There have been many attempts to address this problem, based mainly on the treatment of osteochondritis dissecans, ranging from scientific neglect , debridement and curettage to arthroscopic microfracture, drilling, autogenous bone grafting, allograft transplantation, and carbon fibre resurfacing. In 1991 a paper on osteochondral autograft transplantation for the treatment of osteochondritis dissecans was presented with promising results. In 1993 the first case report on arthroscopic treatment of a chondral lesion in an ACL deficient knee was published.This preliminary report presents surgical technique and purpose-developed instruments for arthroscopic osteochondral autograft transplantation in ACL deficient knees.The series consisted of 11 cases of arthroscopic osteochondral autograft transplantation in conjunction with ACL reconstruction (bone-patella tendon-bone autograft), there were nine primary procedures and two revisions of failed synthetic grafts. Patient age ranged from 22 to 42 years: there were nine men and two women.On arthroscopy before ACL reconstruction, full-thickness crater-like chondral defects larger than 10 mm in diameter, located on the typical weight bearing area of the medial femoral condyle, were considered for chondral autograft transplantation. Lesions in this series were 10-28 mm in diameter. Smaller lesions were microfractured with an arthroscopic awl or drilled with a K-wire. The donor site was selected before notchplasty and three or four osteochondral cylinders, 5 mm in diameter and 10 to 15 mm long were harvested from the anteromedial and superomedial aspect of the notchplasty area. In chronic ACL-deficient knees with a narrow notch and large osteophytes, donor sites for multiple osteochondral cylinders were on the superolateral and anterolateral aspects of the lateral femoral condyle. Initially, autografts were harvested with modified standard 5 and 10 mm bone trephines, but from 1994 thin-walled tubular instruments with fine serrated cutting edges originally designed for ACL reconstruction were specially adapted and were used routinely. The recipient site was prepared in a similar manner and the osteochondral cylinder press-fitted. The bone cylinder removed from the recipient area was routinely inserted in the donor area.DiscussionQuestion. Is it difficult to standardize the groups to be discussed when looking at osteochondritis dissecans?Answer. In this case we looked at ACL against ACL osteochondritis dissecans.Question. Do you use MRI's?Answer. All these studies were with articular cartilage which involved ACL reconstruction quantifying the amount and there was a need to assess the articular cartilage by histological biopsy.Question. Can you fill a large defect?Answer. Technically you can, but only with good instruments and good grafts and without these the technique is very difficult.