Histological Changes in the Human Anterior Cruciate Ligament After Rupture*

Abstract

Unlike extra-articular ligaments that heal after injury, the human intra-articular anterior cruciate ligament forms a layer of synovial tissue over the ruptured surface, which may impede repair of the ligament. Moreover, a large number of cells in this synovial layer and in the epiligamentous tissue express the gene for a contractile actin isoform, alpha-smooth muscle actin, thus differentiating into myofibroblasts. These events may play a role in the retraction and lack of healing of the ruptured anterior cruciate ligament.