Outcome of untreated traumatic articular cartilage defects of the knee: a natural history study.

BACKGROUND: Articular cartilage damage has been reported in 23% of knees with an acute anterior cruciate ligament (ACL) injury and 54% of those with chronic ACL laxity. Because the purpose of surgery is to reconstruct the ACL, the chondral lesion is usually an incidental finding. It is not known if any of the numerous treatments that have been recommended for chondral defects alters the natural history of the untreated lesion. We sought to determine what effect, if any, an isolated articular cartilage defect observed at the time of ACL reconstruction would have on the radiographic, subjective, and objective results after surgery if no intervention was performed on the cartilage lesion itself.
METHODS: From 1987 to 1999, 2770 ACL reconstructions were performed, and 125 of them were done in patients who had an articular cartilage defect of Outerbridge grade 3 or 4 but had both menisci intact. The mean defect size was 1.7 cm (2) (range, 0.5 to 6.5 cm (2) ). Postoperative rehabilitation was not altered because of the chondral defect, and patients were allowed full weight-bearing and the full range of motion of which they were capable. A control group of patients matched on the basis of sex and age at surgery was identified from the database. No patient in the control group had a chondral defect or meniscal tear. Patients were evaluated at one, two, and five years after surgery and every five years thereafter with use of the IKDC (International Knee Documentation Committee) criteria, modified Noyes subjective questionnaire, and radiographs.
RESULTS: Subjective follow-up was carried out more than two years after surgery (mean time, 8.7 years after surgery) for 101 patients. The results of objective evaluation were available for fifty-two patients, at a mean of 6.3 years. The patients in the control group had significantly higher subjective scores than did the patients with a defect in the medial compartment (mean, 95.2 points versus 94.0 points; p = 0.0451) and those with a defect in the lateral compartment (mean, 95.9 points versus 92.8 points; p = 0.0047). There was no significant correlation between larger defect size and lower subjective scores (p = 0.2543). The distribution of IKDC radiographic ratings was not significantly different between the groups. At least 79% of the patients in both groups returned to jumping, twisting, and pivoting sports at least at the recreational level.
CONCLUSIONS: While statistical analysis revealed a difference in subjective scores between the defect and control groups, an average of 93 points for the patients with a lateral defect and 94 points for those with a medial defect indicates that most patients have very few symptoms. This study provides a baseline of information that can be used to compare the results of procedures designed to treat articular cartilage defects.