Relation of the Fibular Head Sign to Other Signs of Anterior Cruciate Ligament Insufficiency

Abstract

The fibular head sign is a clinical finding that seems not to have been previously reported for the diagnosis of chronic anterior cruciate ligament insufficiency (ACLI) associated with lateral rotatory instability of the knee joint. The fibular head could be palpated as a prominent bony lump, felt subcutaneously in the posterior lateral corner of the popliteal fossa. In a prospective study of 20 patients with ACLI, the mean age of the patients (15 males, five females) at the time of assessment was 26 years (range, 18-57 years). The left knee was involved in 11 patients, the right knee in the remaining nine patients. All the patients sustained their knee ligament injury in sporting activities except one patient who was involved in a motor vehicular accident. The majority of the patients had instability-related symptoms for more than six months. After history taking, physical examination in the clinic, and examination under anesthesia, and arthroscopy in the operating room of all patients, it was determined that there were 13 ACL injuries, four posterior cruciate ligament (PCL) injuries, and three combined A/PCL injuries. All ACL injury patients had a prominent fibular head sign. Other associated signs included passive hyperextension of 10-20 degrees, and major anterolateral, and to a lesser degree a posterolateral, rotatory instability. The fibular head sign was negative in isolated posterior cruciate injuries and in combined A/PCL injuries.