Background/Purpose: Degeneration of knee ligaments and tendons, which may be signs of joint instability and abnormal joint loading, may antedate the onset of radiographic accelerated knee osteoarthritis (AKOA) and contribute to prodromal joint symptoms that are common among adults with AKOA. We assessed whether adults with incident AKOA are more likely to have degenerative knee ligaments or tendons compared to adults with common or no KOA at timepoints prior to and after the onset of disease.

Methods: We classified 3 sex-matched groups of Osteoarthritis Initiative participants who had a knee without radiographic KOA at baseline (Kellgren-Lawrence [KL]<2): 1) incident AKOA: ≥1 knee progressed to KL grade ≥3 within 48 months, 2) incident common KOA: ≥1 knee increased in radiographic scoring within 48 months but not meeting AKOA criteria, and 3) no KOA: both knees had the same KL grade at baseline and 48-months. The observation period included up to 2 years before and after when the accelerated or common KOA criteria were met (index visit; no KOA index visit was matched to AKOA). Two musculoskeletal radiologists read magnetic resonance images and reported degenerative signal changes for cruciate and collateral ligaments, extensor mechanism, and proximal gastrocnemius tendons. A degenerative appearance was defined as the presence of abnormal intrinsic high-signal intensity within the substance of the ligaments or tendon without discrete tear. We used generalized linear mixed models with group (3 levels) and time (up to 5 levels) as independent variables.

Results: Table 1 provides the descriptive characteristics of each group. Regardless of time, adults with AKOA had twice the odds of having degenerative cruciate ligaments than those with no KOA (OR=2.10, 95% CI=1.18 to 3.74). A weaker association, which was not statistically significant, was found for those with AKOA versus those with common KOA (OR=1.73, 95% CI=0.99 to 3.02). Adults with common KOA had similar odds of having a degenerative cruciate ligament as those with no KOA (OR=1.21, 95% CI=0.68 to 2.17). Adults with accelerated or common KOA had twice the odds of having degenerative extensor mechanism than no KOA (OR=2.13 and 2.16, respectively). Collateral ligaments and proximal gastrocnemius tendons were not statistically significant.

Conclusion: Degenerative cruciate ligaments and extensor mechanism precede radiographic onset of AKOA. Hence, AKOA may be preceded by knee instability, which may help identify high-risk patients and novel prevention strategies.