Journal of Applied Physiology, Vol 69, Issue 3 902-906, Copyright © 1990 by American Physiological Society
Collagenase activity in anterior cruciate ligament: protective role of the synovial sheath
D. Amiel, E. Billings Jr and F. L. Harwood
Division of Orthopaedics and Rehabiltation, University of California, San Diego, La Jolla 92093.
To evaluate the protective role of the synovial sheath of the anterior
cruciate ligament (ACL), we have developed a synovectomy model that exposes
the ACL substance to the intra-articular environment with and without
hemarthrosis. Histology and the level of collagenase activity were studied
to assess intrinsic ligament alterations. The treatment groups studied were
as follows: ACLs of sham-operated knees receiving arthrotomy only, ACLs of
knees receiving arthrotomy and acute hemarthrosis, ACLs of knees that
underwent synovectomy, and ACLs of knees that underwent both synovectomy
and acute hemarthrosis. All animals were killed 10 days postoperatively for
gross, histological, and biochemical assessment. Histologically at 10 days
ACLs experiencing synovectomy and ACLs having synovectomy plus hemarthrosis
revealed marked hypocellular areas. Biochemical results indicate that
synovectomy is the treatment mainly responsible for the observed increase
in ACL collagenase activity. Hemarthrosis alone clearly had no effect,
although hemarthrosis coupled with synovectomy appeared to further increase
the amount of active collagenase present in the ACLs. This study indicates
that, with exposure of the ACL substance to the synovial fluid or with
hemarthrosis after synovectomy, there is an increase in the degradative
activity of the ACL. The protective role of the synovial sheath suggests
that the synovial sheath injury associated with acute ACL rupture may allow
for exposure of the ligament substance to the degradative effects of the
synovial environment and associated hemarthrosis.
