The Clinical Utility of Thigh Circumferential Measurement in Association with Quadriceps Limb Symmetry.

Background: Thigh circumference is a commonly gathered clinical data point intended to measure muscular atrophy. However, there is limited research examining whether thigh bulk, as observed through circumferential limb measurement, is meaningfully associated with quadriceps muscle strength.

Purpose: To retrospectively assess if a correlation exists between side-to-side difference (SSD) of thigh bulk and limb symmetry index (LSI) with quadriceps isometric strength testing.

Study design: A retrospective, case control study.

Methods: Sixty-seven patients who underwent ligamentous reconstruction completed testing during a six-month post-operative follow-up visit (6.47 +/- 0.79 month). Testing included both clinical and strength measurements. Clinical measurements included side to side thigh bulk circumference difference (SSD) and strength testing included calculated quadriceps strength limb symmetry index (LSI) obtained from isometric testing at 90 degrees of knee flexion performed on an isokinetic dynamometer. Pearson's correlation coefficients were used to assess the relationships between variables.

Results: The principal findings were a mean thigh circumference difference of 2.53 + 1.54 cm and mean quadriceps LSI at time of testing of 66.88 + 16.93%. A moderate, positive relationship was found between thigh circumference difference and the quadriceps LSI (r= 0.36, r2= 0.13, p = 0.003).

Conclusion: A moderate positive correlation between circumference and isometric strength exists that may help clinicians monitor strength differences side to side. Thigh circumference only accounts for approximately ~13% of all factors that influence quadriceps LSI, therefore it is appropriate to incorporate a battery of different tests and measures to properly assess muscular strength following knee surgery.

Level of evidence: Level 3 Evidence.