This study was performed to identify the presence of mechanoreceptors in the tibial remnants of injured anterior cruciate ligaments (ACLs) in human knees by immunohistochemistry.

Twenty-one specimens of tibial remnants of ACLs from patients with ACL ruptures were obtained during arthroscopic ACL reconstruction procedures. As a control, two normal ACL specimens were taken from healthy men at the time of traumatic above the knee amputations. The ACL specimens were serially frozen-sectioned at a thickness of 40micrometer. The average number of sections from each specimen was 71.5 (total 1,502) in the remnant group and 132 (total 264) in the control group. Immunohistochemical staining was used for detection of the neural elements. The mechanoreceptors were identified under a light microscope and their locations and amounts were recorded. An independent sample t-test was used for analysis.

In the remnants of the ACLs, ten mechanoreceptors were identified in 7 (33.3%) out of 21 cases. Nineteen mechanoreceptors were detected in the two normal ACLs, which demonstrated an even distribution at both the tibial and femoral attachments. There was no significant difference between the MR-present group (7 cases) and the MR-absent group (14 cases) with respect to the number of sections, age, and time from injury to surgery.

The identification of mechanoreceptors in the remnants of ruptured ACL specimens could support the necessity for the preservation of the tibial remnant during ACL reconstruction to improve joint proprioception.