The association between anterior cruciate ligament degeneration and incident knee osteoarthritis: Data from the osteoarthritis initiative

Though anterior cruciate ligament (ACL) tear has been widely accepted as an important accelerator for knee osteoarthritis (KOA), the role of intrinsic ACL degeneration in developing KOA has not been fully investigated. To determine whether ACL degeneration, in the absence of ACL tear, is associated with incident KOA over 4 years. Cohort study; Level of evidence, 2. Participants' knees in this nested case–control study were selected from the Osteoarthritis Initiative (OAI) study, with Kellgren–Lawrence grading (KLG) of 0 or 1 ​at baseline (BL). Case knees which had incident KOA (KLG ≥2) over 4 years, were matched 1:1 with control knees by gender, age and radiographic status. ACL signal intensity alteration (0–3 scale) and volume were assessed as compositional feature and morphology of ACL degeneration, using knee MRI at P0 (time of onset of incident KOA), P-1 (1 year prior to P0) and baseline. Conditional logistic regression was applied to analyze the association between measures of ACL degeneration and incident KOA. 337 case knees with incident KOA were matched to 337 control knees. Participants were mostly female (68.5%), with an average age of 59.9 years old. ACL signal intensity alterations at BL, P-1 and P0 were significantly associated with an increased odds of incident KOA respectively (all P for trend ≤0.001). In contrast, ACL volumes were not significantly associated with incident KOA at any time points. ACL signal intensity alteration is associated with increased incident KOA over 4 years, whereas ACL volume is not. The translational potential of this article: This paper focused on ACL signal intensity alteration which could better reflect ACL degeneration rather than ACL tear during the progression of KOA and explored this topic in a nested case–control study. Utilizing MR images from KOA participants, we extracted the imaging features of ACL. In addition, we established a semi-quantitative score for ACL signal intensity alteration and found a significant correlation between it and KOA incidence. Our findings confirmed that the more severe the ACL signal intensity alteration, the stronger relationship with the occurrence of KOA. This suggests that more emphasis should be placed on ACL degeneration rather than ACL integrity in the future.