Association of Fibrosis in the Infrapatellar Fat Pad and Degenerative Cartilage Change of Patellofemoral Joint After Anterior Cruciate Ligament Reconstruction

PURPOSE: The purpose of this study was to evaluate the prevalence and risk factor of cartilage degeneration of patellofemoral joint (PFJ) that was diagnosed by second look arthroscopy in the short term follow-up period. METHODS: One hundred seven patients who underwent ACL reconstruction were evaluated by preoperative MRI, postoperative MRI and second-look arthroscopy. Severity of infrapatellar fat pad (IPFP) fibrosis was evaluated by MRI at average of 26 months after ACL reconstruction. Cartilage degeneration was assessed by second look arthroscopy at 29 months. RESULTS: Twenty-five patients (24.0%) showed cartilage degeneration of PFJ in second look arthroscopy. Patients were divided into 3 groups according to severity of IPFP fibrosis tissue i.e. Group A: focal and incomplete band fibrosis, n=69, Group B: complete band fibrosis, n=31, and Group C: diffuse and infiltrated fibrosis, n=7. Cartilage degeneration of PFJ was significantly worsened with more fibrosis formation of IPFP (p<0.001). Other factors for instabilities, BMI, age, concomitant meniscal procedure, time from injury to reconstruction, severity of IPFP fibrosis of preoperative MRI and clinical scores were not correlated with cartilage degeneration of PFJ. The multivariate logistic regression analysis of degeneration of PFJ after ACL reconstruction identified more severe fibrosis tissue formation of IPFP and initial cartilage defect as significant predictors. CONCLUSIONS: More extensive fibrosis tissue of IPFP and initial cartilage defect related to further degenerative change of PFJ. Age, BMI, concomitant meniscal procedure, time from injury to reconstruction, clinical scores and instability did not affect cartilage degeneration of PFJ in the short term follow-up period.