Chronic musculoskeletal pain and disability dramatically reduce quality and quantity of life worldwide, disproportionately so in low- and middle-income countries. Complementary therapies not typically learned in conventional medical training have much to offer but are under-utilized. Prolotherapy is an injection-based complementary therapy supported by high-quality evidence for osteoarthritis, tendinopathy, and low back pain. Prolotherapy addresses causes of pain and disability at the tissue level, is straightforward to learn, and relies on common, inexpensive material, and requires no refrigeration. Not-for-profit organizations are delivering prolotherapy to underserved patients in low- and middle-income countries through service-learning projects.