Stress plays an important role in the etiology of multiple morbid and mortal outcomes among the living. Drawing on health paradigms constructed among the living augments our evolving knowledge of relationships between stress and health. Therefore, elucidating relationships between stress and both chronic and acute skeletal lesions may help clarify our understanding of long‐term health trends in the past. In this study, we propose an index of “skeletal frailty,” based on models of frailty used to evaluate the life‐long effects of stress on health among living populations. Here, we assess the possible applicability of frailty to archaeological populations. The skeletal frailty index (SFI) is proposed as a methodological liaison between advances made by biological anthropologists studying relationships between stress and health among the living and bioarchaeologists studying stress and health among the dead. In a case study examining skeletal stress in Medieval London, the SFI is applied to nonmonastic (N = 60) and monastic (N = 74) samples. We used analysis of variance/analysis of covariance to compare SFI values between nonmonastic‐monastic groups, sexes, and age cohorts. Results indicate higher lifetime morbidity among monastic groups. These results complement previous bioarchaeological findings on the same London populations, wherein lower risks of mortality and longer lifespans were observed for monastic populations. SFI data reflect the morbidity‐mortality paradox observed in modern populations and accompany recent findings in bioarchaeology of variation in Medieval monastic and nonmonastic “health.” Ultimately, this study demonstrates the SFI's utility in bioarchaeology, through its application of commonly assessed skeletal biomarkers, its ease of applicability, and its potential usefulness for assessing changes in skeletal health over time and across specific geographies.