Ankle dorsiflexion is the upward movement of the foot, bringing the toes closer toward the shin bone (tibia). This motion occurs primarily at the talocrural joint and is essential for nearly all weight-bearing activities. Adequate dorsiflexion is necessary for normal movements like walking and running, allowing the body’s center of gravity to move smoothly over the foot. It is also important for athletic movements such as squatting, lunging, and absorbing impact. When this range of motion is restricted, the body compensates by changing movement patterns at the knee, hip, or lower back, which can increase the risk of injury. Measuring this ankle mobility provides objective data to assess function and identify limitations.
Essential Measurement Equipment
Measuring the ankle’s range of motion typically relies on specialized instruments designed to quantify joint angles. The most common clinical tool is the universal goniometer, which resembles a protractor with two movable arms. This device has a central axis, a stationary arm, and a movable arm, all working together to capture the angle in degrees. The arms are aligned with specific anatomical landmarks on the limb to ensure a standardized measurement.
Another instrument is the inclinometer, which utilizes gravity to measure the angle of a joint relative to the ground. Inclinometers often come in a digital format or as smartphone applications. These tools can offer high reliability and portability. For functional assessments, a simple measuring tape is used to convert distance into a quantifiable metric of mobility.
Non-Weight Bearing Measurement
The non-weight bearing measurement uses a goniometer to isolate movement at the ankle joint, minimizing the influence of body weight and other joints. The subject is usually positioned seated with the knee bent to 90 degrees or lying on their back or stomach with the foot off the edge of a surface. Positioning the knee in a flexed position slackens the gastrocnemius muscle, a major calf muscle that crosses both the knee and ankle, to better isolate the joint’s movement.
The clinician identifies three specific landmarks to align the goniometer. The central axis is placed over the lateral aspect of the lateral malleolus, the bony prominence on the outside of the ankle. The stationary arm is aligned with the midline of the fibula, which runs up the outer calf. Finally, the movable arm is aligned parallel to the base of the fifth metatarsal, the long bone on the outer edge of the foot.
The patient is then instructed to pull the top of the foot toward the shin as far as possible, or the clinician may passively move the joint to its end range. Throughout this process, stabilization of the leg is maintained to prevent any compensatory movement, such as the foot turning outward or the knee extending. The final measurement is read in degrees from the goniometer’s scale, providing a precise measure of the passive or active range of motion available at the joint.
Weight-Bearing Functional Assessment
The weight-bearing functional assessment, commonly called the Knee-to-Wall Test, evaluates dorsiflexion in a position that mimics real-world movements. This test is highly practical and can be performed easily using a wall and a measuring tape. The test begins with the individual facing a wall, placing the foot to be measured flat on the floor perpendicular to the wall.
The subject then lunges the knee forward toward the wall, making sure the heel remains completely flat on the floor. The knee should track directly over the second toe to maintain proper alignment and prevent compensation. If the knee touches the wall easily, the foot is moved back incrementally, typically one or two centimeters, and the lunge is repeated.
The goal is to find the maximum distance from the wall at which the knee can still touch the wall without the heel lifting. This maximum distance, measured from the wall to the tip of the big toe, is recorded in centimeters. The distance measurement provides an objective, functional metric of how much forward translation the ankle joint allows under the body’s weight.
Interpreting Dorsiflexion Results
The numerical results from both measurement methods offer insight into the ankle’s mobility. A typical non-weight bearing range for healthy adults falls around 10 to 20 degrees of dorsiflexion. Measurements below this expected range suggest a restriction that could be related to muscle tightness or joint stiffness. For the functional Knee-to-Wall Test, a measurement of at least 10 to 12 centimeters is generally considered within a healthy range.
Limited dorsiflexion can have consequences that reach beyond the ankle itself, forcing other joints to absorb stress during movement. For instance, a lack of ankle mobility may contribute to the knee collapsing inward during a squat, a phenomenon known as dynamic knee valgus. It is also associated with an increased risk for certain injuries, including Achilles tendinopathy and patellofemoral pain, as the body attempts to find motion elsewhere. If measurements show a significant restriction or a large difference between the right and left sides, consulting a physical therapist or other healthcare professional is the appropriate next step for further evaluation.