Background Sarcopenia, a reduction in skeletal muscle mass and function, is a condition that contributes to functional decline and disability in older adults. Although research on this geriatric condition has developed rapidly in recent years, little work has been done to document whether practicing physicians are incorporating sarcopenia into their clinical practice. Methods An online survey of 253 practicing U.S. physicians assessed knowledge of sarcopenia, use of the term in practice, motivation for screening patients, and diagnostic and treatment approaches. They were board certified in four practice areas: internal medicine (n = 69), family medicine (n = 69), geriatrics (n = 40), or physical medicine and rehabilitation (PM&R) (n = 75). Results Less than 20% of internists and family medicine physicians reported being very familiar with the term sarcopenia, with substantially higher familiarity at this level reported among geriatricians (70%) and among PM&R specialists (41%). Two additional findings pointed to deficiencies in sarcopenia knowledge and practice: participants substantially overestimated the prevalence of sarcopenia in older adults (44% of participants reported an expected prevalence of >25%) compared to findings from published studies (indicating 10% of older adults experience sarcopenia); over 75% reported not typically using specific diagnostic criteria or being unsure if their approach utilized any specific criteria. When asked what terminology they use in a medical chart for a patient presenting with significant loss of muscle mass and strength, only 8% said sarcopenia. Conclusions Sarcopenia, a condition that can have a major impact on older adults as they age, has not been fully incorporated into the knowledge base and practices of active physicians. The survey data suggest that improving physician familiarity with sarcopenia and having universal agreement on criteria for diagnosis may increase the screening for and treatment of sarcopenia.