Comparison of Functional Ankle Motion Measures in Modern Dancers

Ankle injuries are the most common lower extremity injury in dance and sports, often resulting in limitation of dorsiflexion or plantar flexion. Accurate assessment of any limitation in range of motion is an important factor in implementing effective preventative and rehabilitative regimens. Ankle range of motion has traditionally been quantified with goniometers. However, standard goniometry may not be an adequate method of assessing plantar flexion range of motion in dancers. An alternative technique using inclinometers to quantify ankle plantar flexion has been reported, but reliability and inter-instrument correlations for this method are limited. The dorsiflexion lunge distance method has been used to assess ankle dorsiflexion. Although shown to be reliable, this method has not been objectively correlated. The purpose of this study was to determine the most clinically appropriate tool for assessing functional ankle dorsiflexion and plantar flexion in dancers. The aims were to: 1. determine reliability of the weightbearing ankle dorsiflexion lunge method using inclinometer, goniometer, and distance; 2. assess the reliability of inclinometer and goniometer measurements of non-weightbearing active plantar flexion; 3. conduct inter-method and experienced versus novice rater correlations; and 4. determine if a relationship exists between dorsiflexion distance (cm) and dorsiflexion inclinometer angle (degrees) measurements. Twenty-six modern dancers (age: 20.2 ± 1.8 years) participated in the study. Four raters measured weightbearing dorsiflexion in a lunge position using a goniometer, two inclinometer placements, and a distance measurement. They also measured active ankle plantar flexion using an inclinometer placed on the anterior talonavicular joint and a goniometer placed at the lateral ankle. Intra- and inter-rater reliability and inter-method correlations were calculated with Intraclass Correlation Coefficients (ICC) and standard error of measurement (SEM). The relationship of dorsiflexion distance to angle was determined using grouped linear regression (p < 0.05). Dorsiflexion and plantar flexion intra- and inter-rater ICCs for inclinometer, goniometer, and distance ranged from 0.84 to 0.99. The SEM for angular measures ranged from 1° to 3°, and linear measures from 0.3 cm to 0.9 cm. Inter-method correlations ranged from 0.55 to 0.89. There were no differences between inclinometer and goniometer measurement dorsiflexion means. However, inclinometer plantar flexion values were greater than goniometric values (p < 0.001). Experienced raters recorded greater goniometric values compared to novice raters (p < 0.01). There was no consistent linear relationship between dorsiflexion lunge distance measure and inclinometer degrees. It is concluded that functional ankle DF in modern dancers is best quantified using an inclinometer (posterior placement) in the weightbearing lunge position. Non-weightbearing active ankle PF in modern dancers is best quantified with inclinometer placement on the dorsum of the foot. The distance method cannot be compared directly to angular measurement, is subject-specific, and cannot be used as a normative measure to compare DF range between subjects, populations, or age groups.