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

Many patients with anterior cruciate ligament (ACL) deficiency have an abno rmal bone scan. This finding has not yet been explained. Suggested explanat ions in elude intra-articular (structural) or kinematic (functional) abnorm alities. We examined the relationship between bone scintigraphy and cartila ge degeneration or meniscal lesions in the ACL-deficient knee in 95 consecu tive patients who had bone scintigraphy 1-3 days prior to arthroscopic ACL reconstruction. Intra-articular abnormalities of the knee did not explain a ll scintigraphic patterns of this study. We did not find clinically useful positive predictive values for scintigraphic patterns considered to indicat e cartilage degeneration or a lateral meniscus lesion. A clinically useful positive predictive value was found only for medial meniscus lesions when t ime since ACL rupture was more than 18 months, and for local cartilage dege neration when markedly increased uptake was seen when time since ACL ruptur e was more than 4 months. Considering these findings, alternative explanati ons are discussed, based on specific aspects of abnormal kinematics and ada ptive bone metabolism of the ACL-deficient knee.