Ankle Range of Motion (ROM) is a measure of the movement potential at the ankle joint. It is a fundamental tool for assessing joint health and overall lower body function. Measuring ankle ROM is necessary for monitoring recovery after an injury, identifying the cause of mobility limitations, and ensuring proper movement patterns for activities like walking and squatting. Limited ankle movement can force other joints, such as the knees and hips, to compensate, potentially leading to pain or injury elsewhere in the body.
Essential Tools and Preparations
The standard clinical instrument for quantifying joint angles is the universal goniometer. This tool operates much like a protractor with two arms extending from a central axis. The goniometer’s body contains a scale for reading the angle, while the screw-like fulcrum at the center acts as the axis of rotation. One arm is designated as the stationary arm, and the other is the moving arm, which tracks the joint’s movement.
Before measurement, patient positioning is necessary to isolate the ankle movement. For movements like dorsiflexion and plantarflexion, the patient is often positioned lying on their back with the knee slightly bent to relax the calf muscles. The clinician must palpate and mark specific anatomical landmarks, which serve as reference points for aligning the goniometer. Stabilizing the limb above the joint being measured is important to prevent unwanted movement from other joints, such as the subtalar joint, which can skew the reading.
Step-by-Step Measurement Techniques
The ankle joint allows for four primary movements, each requiring precise goniometer placement for accurate measurement. The movements of dorsiflexion and plantarflexion occur mainly at the talocrural joint, which is the articulation between the tibia, fibula, and talus bone. To measure these, the goniometer’s axis is centered over the lateral malleolus.
The stationary arm is aligned parallel to the shaft of the fibula, using the fibular head as a reference point for the upper leg segment. The moving arm is then aligned with the longitudinal axis of the fifth metatarsal. Dorsiflexion, the movement of pulling the toes up toward the shin, is measured by tracking the moving arm as the patient lifts their foot.
Plantarfexlion, the complementary movement of pointing the toes down, is measured from the same starting position and landmarks. The patient is asked to push their foot downward as far as possible, and the moving arm follows the fifth metatarsal axis. Both of these measurements typically begin with the ankle at a neutral position, defined as the foot being at a 90-degree angle to the lower leg.
Measuring inversion and eversion assesses motion primarily at the subtalar joint, which involves the movement of the heel bone. For these movements, the goniometer’s axis is placed on the posterior aspect of the subtalar joint, approximately at the level of the malleoli. The stationary arm is aligned with a line that bisects the back of the lower leg, providing a stable reference. The moving arm is aligned with a line bisecting the calcaneus, or heel bone. Inversion is the movement of turning the sole of the foot inward, while eversion turns the sole outward.
Interpreting the Measured Range
The numerical values recorded from the goniometer are compared against normative data to understand the ankle’s mobility status. The range for plantarflexion is approximately 40 to 50 degrees. Dorsiflexion normally falls between 15 and 20 degrees when measured non-weightbearing.
The lateral movements of the heel have smaller ranges, with inversion measuring around 20 degrees and eversion ranging from about 16 to 21 degrees. Women, for example, have been observed to have slightly greater inversion and eversion ranges compared to men.
A measurement falling below the normative range indicates restricted ROM, suggesting potential issues like joint stiffness, muscle tightness, or the presence of scar tissue. Limited dorsiflexion often points to tightness in the calf muscles, specifically the gastrocnemius or soleus. Conversely, a measurement significantly higher than the normative data may suggest joint hypermobility or ligamentous laxity. Interpreting these numbers provides a clinical basis for determining treatment plans aimed at restoring or maintaining optimal ankle function.