Introduction: Sarcopenia is a systemic condition linked to increased morbidity and mortality in older adults. Point-of-Care Ultrasound (POCUS) offers a rapid, bedside method to assess muscle mass. This study evaluates the diagnostic accuracy of POCUS compared to Dual-energy X-ray Absorptiometry (DXA), the gold standard method, and explores its prognostic value in old patients undergoing surgery for hip fractures. Patients and Methods: In this prospective, single-center study, 126 patients aged ≥ 70 years and hospitalized with hip fractures were included. Sarcopenia was defined according to the revised 2018 EWGSOP2 criteria. Muscle mass was assessed by the Appendicular Skeletal Muscle Mass Index (ASMI) using DXA and by the thickness of the rectus femoris (RF) muscle using POCUS.

Results: Of the 126 included patients, 52 had both DXA and POCUS assessments, and 43% of them met the diagnostic criteria for sarcopenia or severe sarcopenia. RF muscle thickness measured by POCUS was significantly associated with ASMI (R2 = 0.30; p < 0.001). POCUS showed a fair diagnostic accuracy in women (AUC 0.652) and an excellent accuracy in men (AUC 0.905). Optimal diagnostic thresholds according to Youden’s index were 5.7 mm for women and 9.3 mm for men. Neither RF thickness, ASMI, nor sarcopenia status predicted mortality or major postoperative complications.

Conclusions: POCUS is a promising, accessible tool for diagnosing sarcopenia in old adults with hip fractures. Nonetheless, its prognostic utility remains uncertain and should be further evaluated in long-term studies.