Intrarater test-retest reliability of hip range of motion and hip muscle strength measurements in persons with hip osteoarthritis.

OBJECTIVE

To examine the relative and absolute intrarater test-retest reliability of muscle strength and range of motion (ROM) measurements of the hip performed in people with hip osteoarthritis.

DESIGN

Repeated measures.

SETTING

Human movement laboratory of a university.

PARTICIPANTS

Participants (N=22; 10 men, 12 women; age range, 50-84y) with hip osteoarthritis.

INTERVENTIONS

On 2 separate occasions, at least 1 week apart, isometric torque measurements were obtained from the hip rotators, flexors, abductors, and extensors. Passive ROMs in hip rotation, flexion, abduction, and extension were also determined.

MAIN OUTCOME MEASURES

Relative reliability was estimated using the intraclass correlation coefficient, model 2,2 (ICC(2,2)). Absolute reliability was estimated using the coefficient of variation (CV) and the standard error (SE) of measurement.

RESULTS

For measurements of muscle strength, ICC(2,2) ranged from .84 to .97, and the CV ranged from 8% to 15.7%. Hip extensors and internal and external rotators showed high ICC(2,2) (>.96) and low CV (<9.8%); hip abductors showed the lowest ICC(2,2) (.84) and the highest CV (15.7%). For ROM measurements, ICC(2,2) ranged from .86 to .97 and SE ranged from 3.1 degrees to 4.7 degrees . Hip flexion ROM showed the highest ICC(2,2) (.97) and an SE of 3.5 degrees ; hip extension ROM showed the lowest ICC(2,2) (.86) and the highest SE (4.7 degrees ).

CONCLUSIONS

Strength and ROM testing of the hip in people with hip osteoarthritis can be performed with good to excellent reliability.