A muscle’s orientation and reference length of sarcomeres (referred to as the muscle architecture) can be used to predict the functional capability of a muscle. Measurements for muscle architecture include fascicle length, sarcomere length, and the muscle mass. Sarcomere length is then compared to the force-length relationship for human muscle.

The current study examined the deep external rotator muscles of the hip (DERMH), photographing their pathway in situ, and excising the muscles from 12 cadavers [n = 12, 6 male:​6 female aged 56-88 years (Mean = 79.25 years)] to measure sarcomere length, fascicle length and mass. These values were used to calculate physiological cross-sectional area (PCSA) and normalized fascicle length (LFn) to predict the functional capability of the six DERMH. The data are valuable to predict changes in the muscles’ behavior during movement of the hip joint, or after being displaced from their anatomical attachments such as during total hip arthroplasty surgery