Table 1.

Description of measures of performance-based and self-reported physical function, psychological factors, and physical impairments

Performance-Based Physical Function
Figure-of- 8 Walk Test	Subject stood in the middle of two markers 1.5m apart. On command “go”, subject walked in one continuous figure-of-8-pattern around the markers, and ended at the starting position. Time to complete the task was recorded. Reliability of test in our department is good (ICC=.90).9
Timed Chair Rise	Subject was seated in a chair without armrests with arms crossed over the chest. Subject was timed while rising to a full upright position and sitting down 5 times without assistance. Reliability in older adults is good (ICC=.84 to .92).7
Gait Speed	Recorded time needed to pass two infra-red beams 4m apart, located in the central part of a longer path of 7m. Measured at two paces: self-selected and fast speeds. For each pace the subject was timed twice and the fastest speed was recorded (m/sec). Reliability of self-selected gait speed in old adults is good (ICC=.84).10
Self-Reported Physical Function
WOMAC- PF	Western Ontario and McMaster Universities Osteoarthritis Index-Physical Function (WOMAC- PF) is a valid disease-specific measure of physical function in individuals with knee and/or hip OA.11 It has 17 items. Subject ranks the difficulty during performance of functional activities on a 5-point scale. Scores range from 0–68. Higher scores indicate worse physical function.
LEFS	Lower Extremity Function Scale (LEFS) is a region-specific measure of lower extremity function with adequate reliability and validity.12 The scale consists of 20 items, each scored from 0–4. Total scores range from 0 to 80. Higher scores indicate better physical function.
Psychological Factors
Fear of Falling	Measured by the Survey of Activities and Fear of Falling in the Elderly (SAFFE). It measures 11 basic and instrumental activities of daily living, as well as more advanced mobility and social activities. Scores range from 0–3. Higher scores represent more fear of falling. SAFFE was validated in community-dwelling older adults.9
Depression	Measured by the Center for Epidemiological Studies Depression Scale short version including 10 questions (CES-D 10). It is a reliable and valid measure of depression symptoms.13 Scores range from 0–30. Higher scores represent more depression.
Anxiety	Measured by the State Trait Anxiety Inventory (10-item), which is a reliable and valid measure.14 Scores range from 4–40. Higher scores coincide with greater anxiety.
Muscle Strength
Tested using an isokinetic dynamometer (Biodex System-3 Pro, Shirley, NY). Measures recorded in torque (Nm) and normalized to body mass (Nm/kg). Subject performed 3 warm-up trials and 5 testing trials of maximum voluntary isometric contraction. Reliability of these measures are good (ICC=.86 to .93).15–17
Knee Extension	Subject was seated with the tested knee flexed at 60° and the force-sensing arm secured to the ankle. The highest torque was used in the analysis.
Hip Extension	Subject was in supine with the hip flexed at 50° and trunk flexed at 30°. The force-sensing arm was attached to the posterior thigh (proximal to the popliteal fossa). The average of 3 trials was used in the analysis.
Hip Abduction	Subject in side lying, tested hip up. The testing hip was at 0° of abduction, 5° of extension, and the knee was extended. The force-sensing arm was proximal to the lateral knee joint line. The average of 3 trials was used in the analysis.
Range of Motion
Knee Flexion and Extension	Measured passively with a standard goniometer. Subject in supine, axis of goniometer aligned on the center of the lateral epicondyle (femur). Distal and proximal goniometer arms were aligned with the lateral malleolus and the greater trochanter respectively. For terminal knee extension, a bolster was placed under the heel to allow knee hyperextension. Technique has good reliability (ICC=.96 for flexion and .81 for extension).18