Assessment of hip and knee muscle function in orthopaedic practice and research.

Isometric evaluation of hip and knee muscle strength can be a useful objective assessment tool in the clinic and may be preferred over other forms of dynamic muscle testing, such as isokinetic assessment or variable-resistance weight-lifting. Assessment of isometric strength with use of a handheld dynamometer requires little skill and is easily administered, relatively inexpensive, valid, reliable, and functional; thus, it could be easily integrated into routine clinical examinations. Surface electrical stimulation, electromyography, and ultrasonography can be used in conjunction with isometric muscle testing for the identification of neuromuscular factors influencing muscle force generation. Further research is warranted to investigate the neural and/or muscular impairments associated with hip and knee muscle weakness in orthopaedic populations, with the ultimate goal of improving rehabilitation strategies.