The Presence of Mechanoreceptors and Cortical Connections Support a Proprioceptive Role for Knee Plicae.

Purpose: To determine histologically and electrophysiologically whether the plicae have a proprioceptive function. Methods: Tissue samples were obtained from 36 plicae in 29 knees (including 7 bilateral cases). The samples included 20 suprapatellar, 10 medial patellar, and 6 infrapatellar plicae. Kim and Choe's classification was used to describe the patterns of the plicae. Results: Twenty-nine patients who underwent knee arthroscopy were included in the study. Of these, 14 knees were on the left side and 15 on the right. The patients' ages ranged from 12 to 78 years (mean age, 42 years). Golgi tendon organs (type III) were the most frequently observed mechanoreceptors. No free nerve endings (type IV) were identified in any of the plicae. Electrical stimulation of 4 plicae and 2 anterior cruciate ligaments was performed, and accurate, expected responses were obtained. Conclusions: Histologic and neurophysiologic findings have shown the presence of mechanoreceptors in the knee plicae. Following the identification of these mechanoreceptors, the establishment of a neural connection between the plicae and the cerebral cortex suggests that the plicae are functional structures involved in proprioception. However, free nerve endings were evaluated in limited numbers and could not be shown. Clinical Relevance: Plicae in the knee are considered rudimentary structures with the potential to become pathological. However, the plicae may not be useless structures but may improve the proprioceptive ability of the knee.