Project Summary/Abstract Myofascial pain remains an underdiagnosed contributor to a range of musculoskeletal pain conditions. The lack of validated biomarkers limits the ability to objectively detect myofascial pain, probe underlying pain mechanisms, and guide targeted treatments. This proposal will address this gap by quantifying the biochemical, biomechanical, and structural properties of myofascial pain using advanced, quantitative imaging techniques. As a model of myofascial pain, we have chosen plantar fasciitis, which affects 1 out of every 10 adults. Our long-term goal is to enhance musculoskeletal pain management by creating better tools for detecting abnormal myofascial tissue that enable more individualized treatment. The objective of the R61 phase is to use novel imaging techniques to develop a diagnostic biosignature to objectively and accurately determine the location and severity of abnormal myofascial tissue. Our approach will use a cross-sectional study design with 3 groups: plantar fasciitis (n=50), Achilles tendinopathy (n=25), and pain-free controls (n=25) to test Specific Aim 1: Develop a diagnostic imaging biosignature of myofascial tissue to differentiate individuals with plantar fasciitis from other foot pain without a myofascial component (Achilles tendinopathy) and from matched pain-free controls. The objective of the R33 phase is to use novel imaging techniques to develop a predictive biosignature to identify individuals most likely to respond to DN, and a response biosignature to guide dosing or continued use of DN for myofascial pain for individuals with plantar foot pain. Our approach will use a parallel-group, doubleblinded randomized controlled trial (RCT) design with imaging measured before, during (1 m.), and after treatment (3 & 6 m.). Participants will be randomized to one of two groups: 1) DN + standard care, or 2) Sham DN + standard care to test Specific Aim 2: Determine 2A) predictive (Independent variable: imaging biosignature; Primary outcome: Pain Intensity) and 2B) response (Independent variable: DN vs. Sham DN; Primary outcome: Imaging biosignature/biomarkers) imaging biosignatures in an RCT. Exploratory Aim 3: Will develop composite biosignatures, that combine multiple imaging biomarkers developed in Aims 1 or 2 with psychosocial factors, to enhance the diagnostic, predictive, or response capability for myofascial pain. Transition criteria. 1) Adequate recruitment with >90% of participants in each group enrolled; 2) Adequate representation with neither sex exceeding 60% of the sample; 3) Minimal missing data (<5%) for collected outcomes; 4) At least 2 diagnostic imaging biomarkers with an ROC AUC > 0.7 and FDRs < 0.1; 5-8) Submit DSMP, Study Accrual and Retention Plan, Final sample size and statistical analysis informed by mock recruitment, and R33 transition application, including implementation of an effective sham DN.