EARLY DETECTION OF KNEE OA – THE ROLE OF A COMPOSITE DISEASE ACTIVITY SCORE: DATA FROM THE OSTEOARTHRITIS INITIATIVE

INTRODUCTION

BM lesions and effusion-synovitis are frequent and dynamic disease processes detected from early- to late-stage knee OA. These processes are associated with knee symptoms, representing the primary clinical manifestations of OA. Through a systematic and iterative process, we previously developed and validated a composite biomarker – the disease activity score – that combines BM lesions and effusion-synovitis volumes throughout a knee into an efficient continuous single score.

OBJECTIVE

To evaluate whether dynamic disease processes (effusion-synovitis volume and BM lesions), summarized by a validated efficient continuous composite score, are present in early OA and prognostic of incident symptomatic knee OA over the subsequent three years.

METHODS

We analyzed a convenience sample within the OAI of participants without symptomatic knee OA. Pain assessments and radiographs were collected annually. Among 913 knees (n=572 participants), most were female, white, and had a mean age of 61 (SD=9) and body mass index of 29.4 (SD=4.5) kg/m². MR images were collected at each OAI site using Siemens 3.0 Tesla Trio MR systems. We measured BM lesion and effusion-synovitis volumes on a sagittal IM fat-suppressed sequence (field of view=160mm, slice thickness=3mm, skip=0mm, flip angle=180 degrees, echo time=30ms, recovery time=3200ms, 313 × 448 matrix, x-resolution=0.357mm, y-resolution=0.357mm). Using MR images from the initial visit, we combined effusion-synovitis and BM lesion volumes to calculate a composite score, referred to as the disease activity score. A disease activity score of 0 approximated the average score for a reference sample (n=2,787, 50% had radiographic knee OA, average [SD] WOMAC pain score = 2.8 [3.3]); lower scores (negative scores) indicate milder disease, while greater values indicate worse disease. The outcome was incident symptomatic knee OA (the combined state of frequent knee pain and radiographic OA [KLG≥2]) within three years after the disease activity measurement. We used logistic regression with repeated measures to assess the association between disease activity (continuous measure) and incident symptomatic knee OA, adjusting for gender, age, and body mass index.

RESULTS

Disease activity ranged from -3.3 to 31.1 (lower values = less effusion-synovitis and BM lesions). Knees that developed incident symptomatic knee OA had greater disease activity (-0.3 [2.7] vs. -1.1 [2.8]): the adjusted relative risk=1.06 (per 1 unit of disease activity; 95% confidence interval: 1.02-1.10). Our stratified analyses revealed those with only radiographic OA (adjusted relative risk=1.37 [1.06-1.78]) or only symptoms (adjusted relative risk=1.15 [1.03-1.28]) at baseline drove the associations between disease activity and incident symptomatic knee OA.

CONCLUSION

Our findings underscore the critical role of the composite disease activity score in the early detection of knee OA. By integrating BM lesions and effusion-synovitis volumes, this score provides a powerful prognostic tool, enabling timely intervention to potentially alter the disease trajectory. These insights pave the way for targeted therapies that address inflammation and bone turnover, offering hope for improved patient outcomes.