Abnormal bone scans in anterior cruciate ligament deficiency indicate structural and functional abnormalities

Many patients with anterior cruciate ligament (ACL) deficiency have an abnormal bone scan. This finding has not yet been explained. Suggested explanations include intra-articular (structural) or kinematic (functional) abnormalities. We examined the relationship between bone scintigraphy and cartilage degeneration or meniscal lesions in the ACL-deficient knee in 95 consecutive patients who had bone scintigraphy 1-3 days prior to arthroscopic ACL reconstruction. Intra-articular abnormalities of the knee did not explain all scintigraphic patterns of this study. We did not find clinically useful positive predictive values for scintigraphic patterns considered to indicate cartilage degeneration or a lateral meniscus lesion. A clinically useful positive predictive value was found only for medial meniscus lesions when time since ACL rupture was more than 18 months, and for local cartilage degeneration when markedly increased uptake was seen when time since ACL rupture was more than 4 months. Considering these findings, alternative explanations are discussed, based on specific aspects of abnormal kinematics and adaptive bone metabolism of the ACL-deficient knee.