Acute injury of the articular cartilage and subchondral bone: a common but unrecognized lesion in the immature knee.

OBJECTIVE

We studied the prevalence of injuries of the articular cartilage and subchondral bone after acute trauma in skeletally immature knees using high-resolution MRI.

MATERIALS AND

METHODS

We reviewed knee MRIs of 126 young children and adolescents suspected to have internal knee derangement, including 82 with open physes and a control group of 44 who were skeletally mature. High-resolution proton density and T2-weighted pulse sequences were used in all patients. The prevalence of common injuries in the two groups was compared using chi-square analysis. Levels of interobserver agreement for evaluation of chondral lesions in the skeletally immature group were determined using the kappa statistic.

RESULTS

In the skeletally immature group, chondral lesions were the most prevalent injuries (prevalence = 0.34, p = 0.009) followed by meniscal and anterior cruciate ligament injuries (prevalence = 0.23 and 0.24, respectively). No significant difference in the prevalence of chondral injury before and after physeal closure was seen (p = 0.45). There was no significant difference in the prevalence of anterior cruciate ligament injuries between the two groups, but meniscal injuries were more prevalent in the skeletally mature patients (prevalence = 0.41, p = 0.037). Interobserver agreement for chondral injuries in the group with open physes was good (weighted kappa = 0.45-0.51).

CONCLUSION

The most common injuries occurring as a result of acute trauma to the immature knee were chondral. In patients with open physes, chondral injuries were significantly more prevalent than anterior cruciate ligament and meniscal injuries.