Prevalence of structural lesions and osteoarthritis in femorotibial joints of asymptomatic participants from the lausanne knee study

Structural lesions of the cartilage, menisci, and bone are prevalent on knee MRIs in the asymptomatic population. The presence of such lesions may lead to the diagnosis of osteoarthritis (OA) according to imaging criteria. The prevalence of OA at imaging may depend on the definition criteria used (radiographic vs. MRI criteria). 1) To determine the prevalence of structural lesions of the femorotibial joint in two groups of young and older asymptomatic participants with healthy knees from the Lausanne Knee Study (LKS). 2) To determine the prevalence of OA in that population using radiographic and MRI definitions of OA. Asymptomatic volunteers were prospectively enrolled in this IRB-approved HIPPA-compliant study. Inclusion criteria: age between18-35 or 45-70 years, no knee symptoms in the past 12 months, no history of severe lower limb injury requiring surgery or not, no impairment that might affect gait, BMI≤30. All participants (n=430, 47.8 years ±16.17 (SD), range 18-70 y, 192 (44.6%) male) underwent a clinical evaluation, including KOOS and WOMAC scores to evaluate pain and knee function, radiographic imaging (weight-bearing Schuss and lateral radiographs of both knees, full spine and lower extremity weight-bearing low dose 3D biplanar radiographs (EOS)), and 3T MRI of a randomly selected knee. MRI protocol included 2D fat-suppressed FSE IW images (sagittal, coronal, and transverse planes), isotropic 3D DESS, high-resolution 3D T1. One musculoskeletal radiologist with 6 years of experience graded radiographs (KL score) and knee MRIs for all structural lesions included in the MOAKS criteria. For this study, only femorotibial compartments will be presented. OA was defined as a KL score≥2 at radiography, or using the criteria proposed by Hunter et al (2011) at MRI. There were 137 participants in the young (Y) (26.2y±4.7; 65 male (47.4%)) and 293 in the older (O) group (57.9y±7.23; 127 male (43.3%)). Participants had no knee pain or functional impairment (average KOOS 97.6±2.51 vs 97.2±3.78 in Y vs O group (p=0.26); average WOMAC 97.8±5.48 vs 96.7±8.23 in Y vs O group (p=0.16)). Structural lesions were highly prevalent in the femorotibial joints (decreasing order of prevalence): 190 (44.2%) cartilage damage (7 vs 183 in Y vs. O, p<10−5), 132 (30.7%) BML (5 vs 127 in Y vs. O, p<10−5), 111 (25.8%) meniscal damage (2 vs 109/ in Y vs. O, p<10−5), 110 (25.6%) had peri-articular cysts (13 vs 97 in Y vs. O, p<10−5), 104 (24.2%) participants had osteophytes (3 vs 101/ in Y vs. O, p<10−5), 68 (15.8%) Hoffa synovitis (3 vs 65 in Y vs. O, p<10−5), 38 (8.8%) synovitis/effusion (3 vs 35 in Y vs. O, p<10−3), and 17 (4%) had loose bodies (1 vs 16 in Y vs. O, p=0.019). 76 (17.7%) participants (1 young) had radiographic OA (60 KL2; 16 KL3; 0 KL4), while 24 (5.6%) participants (all from the older group) had femorotibial OA based on MRI criteria, 198 (46%) had normal MRI, and 208 (48.4%) had structural lesions of variable severity that did not fulfill MRI criteria of OA. In a cohort of 430 asymptomatic volunteers with clinically healthy knees, structural lesions were present in up to 54% of femorotibial joints, with their prevalence increasing with age. The prevalence of OA at imaging in healthy knees may be high and depends on the criteria used (prevalence of 5.6% vs. 17.7% when using MRI vs. radiographic criteria).