Destruction of attachment of the anterior cruciate ligament (ACL) was studied. The tibial attachments of the ACLs from 32 rheumatoid knees taken during total knee replacement were examined by light microscope. Sections of samples were stained with hematoxylin-eosin (H. E.) and peroxidase anti-peroxidase (PAP) methods.
The destructive changes of ligament attachments were degeneration of collagen fibers, disappearance of fibrocartilage zone and mineralized fibrocartilage zone, increase of fibroblast-like cells at the area of ligament insertion, change and disappearance of tide mark, invasion of fibrous granulation tissues, bone trabecular thinning, inflammation of intramedullary space, and proliferation of blood vessels at the ACL with granulation tissues.
Statistical examination of these findings showed that the condition of tide mark is characteristic in destruction of the enthesis of rheumatoid knees. Calcification and ossification of the enthesis were not observed, and turnover of the enthesis can be very active. On the other hand, large monocytes and fibroblast-like cells at the area invasived by fibrous granulation tissues have positive staining for lysozyme by PAP method. Monocytes and chondrocytes at the area remained in the fibrocartilage zone and mineralized fibrocartilage zone were positive for S-100 protein. The present pathological study of the ACL destruction of the rheumatoid knees confirmed that tide mark is very peculiar in the changes of the enthesis. Invasion of the granulation tissues from intramedullary space can also be a cause to destruct the ligament attachment.
rheumatic knee joint
anterior cruciate ligament