[Relationship between fabella and posterolateral knee pain and common peroneal nerve injury].

Objective: To analyze the incidence and characteristics of fabella in the Chinese population and its correlation with pain in the posterolateral region of the knee joint and common peroneal nerve palsy.
Methods: Total 732 patients including 405 males(450 knees) and 327 females(383 knees) who underwent unilateral or bilateral knee MR imaging from September 2015 to July 2019 were retrospectively evaluated. The basic information of all patients was extracted from the hospital's his system. The patient's medical records were checked by telephone follow-up or his system, and the number of patients with posterolateral knee pain and common peroneal nerve paralysis were recorded.
Results: The overall prevalence of fabella was 48.38%, 23.53% in men and 24.85% in women, there was no significant difference between them ( P >0.05). All the subjects were divided into five age groups. The prevalence of fabella was significantly different among different age groups:6.6% in 20 year-old group, 33.8% in 21 to 34-year-old group, 53.5% in 35 to 44-year-old group, 57.5% in 45 to 59-year-old group and 73.9% in ≥ 60-year-old group, the difference was statistically significant ( P <0.001). There was a significant correlation between the prevalence of fabella and the age of patients. With the increase of patients' age, the prevalence of fabella in knee joint also showed an obvious upward trend ( P <0.001). According to the presence of fabella in the knee joint, 232 cases of knee joint pain were found, accounting for 57.57% of the patients with fabella, accounting for 27.85% of the total data( P <0.01). The correlation score analysis was R =1.546, P <0.01;when the presence of fabella in the knee joint, a total of 44 cases of common peroneal nerve paralysis occurred in the knee joint, accounting for all knees 28% of the total knee joint, and 29 cases of common peroneal nerve palsy (3.48% of the total knee joint) were found when there was no fabella in the knee joint( P <0.05). The correlation score analysis was performed with R =1.695, P <0.05.
Conclusion: The prevalence of fabella us in Chinese population is 48.38%. There is no relationship between the incidence of gastrocnemius and gender, but the incidence of fabella is positively correlated with age, pain in the posterolateral region of the knee joint and the occurrence of common peroneal nerve symptoms.