Impact of infrapatellar fat pad injury severity on subsequent patellofemoral cartilage degeneration following acute ACL tear.

Objective: The infrapatellar fat pad (IFP) is important in the homeostasis of the knee joint due to its structural and immune-modulating properties. This study investigates the relationship between IFP injury severity during acute Anterior Cruciate Ligament (ACL) tears, and the future development of Patellofemoral Compartment (PFC) chondrosis. Methods: Adult participants aged 18-45 years old who were known to have first-time ACL tears between 01/01/2009 and 10/1/2022 were included. Patients with concomitant knee pathologies at the time of injury were excluded from the study. All participants received ACL reconstruction surgery and had follow-up MRIs conducted within two years postoperatively. Preoperative IFP edema levels were assessed alongside both pre-and postoperative PFC. We analyzed the relationship between the initial IFP edema and future PFC progression on subsequent MRI scans. Results: A total of 69 participants were included in this study. No significant correlation was found between the severity of initial IFP injury and the initial presence of PFC chondrosis (r = -0.04, P = 0.61). However, a significant positive correlation was observed between the severity of initial IFP injury and the future progression of PFC chondrosis (r = 0.44, P < 0.001). Additionally, a significant difference in the progression of PFC chondrosis was noted when comparing grade 1 to grade 2 IFP injuries (P = 0.001). No significant difference in PFC chondrosis development was identified when comparing grade 2 to grade 3 IFP injuries (P = 0.72). Conclusion: Our study underscores the potential role of the IFP in preserving cartilage homeostasis by establishing a link between the severity of IFP injury and the subsequent development of PFC following ACL injury.