BACKGROUND: Mechanoreceptors in the posterior cruciate ligament (PCL) can produce proprioception, which is an important reason why patients choose cruciate-retaining total knee arthroplasty (TKA). The number of mechanoreceptors in the PCL of patients with knee osteoarthritis (OA) is unknown. PURPOSE: To provide a theoretical basis for estimating the number of mechanoreceptors in the PCL by evaluating the relationship between this number and patient age or OA severity. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: An overall 28 PCLs from patients with knee OA were collected at the time of TKA and grouped according to patient age (group A, 60-69 years [n = 8]; group B, 70-79 years [n = 12]; group C, ≥80 years [n = 8]) and OA based on Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (group I, ≤80 [n = 8]; group II, 81-120 [n = 10]; group III, >120 [n = 10]). Hematoxylin and eosin and S-100 immunohistochemical staining were performed on the slices near the tibial attachment of the PCL, and the number of mechanoreceptors in each slice was counted. Multifactor analysis of variance was used to evaluate the relationship between the number of mechanoreceptors and patient age or WOMAC score. RESULTS: The number of mechanoreceptors (mean ± SD) in groups A, B, and C was 24.00 ± 15.19, 30.92 ± 11.41, and 23.38 ± 11.39, respectively, with no significant between-group differences. The number of mechanoreceptors in groups I, II, and III was 43.50 ± 4.99, 25.00 ± 5.27, and 15.20 ± 5.61, with significant differences between groups I and II, groups I and III, and groups II and III ( < .001 for all). CONCLUSION: In patients with knee OA, age had no significant effect on mechanoreceptor count, but the number of mechanoreceptors in the PCL decreased significantly with higher (worse) WOMAC score. These findings suggest that in patients of any age with high WOMAC scores, there may be little value as it relates to knee proprioception in performing a PCL-retaining TKA.