Preoperative MRI underestimates articular cartilage defect size compared with findings at arthroscopic knee surgery.

Background: Magnetic resonance imaging (MRI) is widely used as a preoperative tool to estimate the size of articular cartilage defects to optimize treatment selection. However, the reliability of MRI sizing of cartilage defects is not well understood. Hypothesis/

Purpose: The purpose of this investigation was to compare the size of knee articular cartilage defects on MRI to arthroscopic visualization after debridement.