Anterior cruciate ligament innervation in primary knee osteoarthritis

To relate the Anterior Cruciate Ligament (ACL) innervation and histologic degeneration status to the knee osteoarthritis radiologic and functional status.

Prospective observational study including 30 consecutive patients affected by primary knee osteoarthritis undergoing Total Knee Arthroplasty (TKA). All patients suffering secondary knee osteoarthritis, an antecedent of an infectious process, malignant process, autoimmune disorder, or previous knee surgery were excluded. We recorded biodemographic, clinical, and radiologic variables of all participants previous to the TKA procedure. ACL tissue was harvested during TKA standard procedure and the obtained sample was fixed in 4% formalin and paraffin-embedded. ACL cross-sections were stained by haematoxylin-eosin and Gallego staining for elastic and collagen fibers, and Sevier-Munger silver staining for nervous tissue.

ACL samples histologic degeneration classification reported 15.4% normal, 23.1% slight, 26.9% mild, 11.5% moderate and 23.1% marked. We noted 46.2% large nervous fascicles, 15.4% medium fascicles, 3.8% small fascicles, and no nerve fibers were found in 34.6% ACL samples. No significant correlation was found between the histologic degeneration and the nervous fiber quantification (p>0.05, in all cases). We noted a significant histologic degeneration inverse correlation with the VAS scale (p=0.016), and nervous fiber quantification correlation with Lequesne maximum distance walked punctuation (p=0.043). We also noted greater nervous fiber quantification with minor radiological knee osteoarthritis (Kellgren-Lawrence grade II).

ACL degeneration and innervation deficit may play a role in primary knee osteoarthritis onset, but the lack of a defining relationship among the different parameters assessed justifies further research in greater populations.