Weber MA, Snyder MJ, Workman KK, et al. - This study was sought to compare variations between asymptomatic and symptomatic adverse local tissue reactions (ALTR) in an observational cohort, including presentation, metal ion differences, and metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) findings. Researchers conducted a retrospective review of an observational cohort including a total of 492 metal-on-polyethylene (MoP) total hip arthroplasty (THA) patients at elevated risk of developing ALTR. For ALTR, 94 individuals had undergone revision arthroplasty. Individuals were classified into symptomatic and asymptomatic ALTR groups. They compared presentation, metal ion levels, and imaging findings. It was shown that almost half of the MoP THA ALTR cases identified were asymptomatic. Between symptomatic and asymptomatic pseudotumor formation, cobalt levels could not differentiate. The data reveal that symptomatic and asymptomatic MoP ALTRs have similar MARS MRI characteristics. This is necessary to risk-stratify individuals who could potentially have ALTR based on implant type, symptoms, ion levels, and MARS MRI.