Common Misconceptions in Measuring Lower Extremity Flexibility in Pediatric Patients

There are routine tests and measures that are completed with kids at school to screen for risks of limited mobility or deformity. One example is the sit and reach test to assess trunk and lower extremity mobility.

While this test is usually easy to apply with limited training required, there are some shortfalls that do not allow correct assessment of mobility.

Flexibility: What is “Normal”?

There are different versions of the sit-and-reach test. The classic version is positioning the patient in long-sitting or sitting upright with their legs straight. The observer monitors the patient’s movement in reaching forward with their hands to see if they can reach their toes.

The modified version uses a box with a ruler on top. In the long-sitting position, the patient reaches with their fingers to slide forward on top of the box. A value is determined based on where they reach. This is then compared to standardized values for other kids their age.

Unfortunately, these tests are completion based tests. The only thing the patient has to do is complete the test. The test does not measure “how” they were able to reach their toes aside from keeping their knees straight. The tester does not have to observe where the motion comes from, be it their hips, knees, or back.

Observing Back Mobility

A patient completing the sit and reach test with a distance within a normative value of other kids their age is a passing grade, so to speak. However, this does not give us the full idea of where their movement is occurring. A child with limited hamstring mobility could still reach their toes with increased trunk mobility through the thoracic and lumbar spine, as well as increased pelvic mobility.

Recent research has found that decreased hamstring extensibility can influence pelvic and lumbar movement when someone performs trunk flexion.¹ The body will compensate for the lack of hamstring extensibility by moving at adjacent segments in the spine.² Unfortunately, increased spinal flexion and posterior pelvic tilting can result in overloading the spine,³ creating a possibility of increased risk of injury. Taking this into account, alternative methods of testing extremity mobility should be considered.

Alternative Tests

If we’re looking to assess hamstring mobility, two alternative test can be performed:

The Straight Leg Test

During the straight leg raise test, the tester raises the leg with the knee extended and measures an angle along the trunk through the long axis of the leg.

90-90 Hamstring Length Test

The 90-90 test is measured at the knee. The patient’s knee and hip are placed at a 90-degree angle to start. Then, the patient’s leg is extended until an appropriate “stretch” is felt. An angle is then measured along the long axis of the thigh and long axis of the leg.

Both tests position the patient in supine, which assists with stabilizing the lumbar spine for limited movement.

These tests provide an adequate assessment of hamstring flexibility with easy application and limited risk of error. Also, patients can complete each at home as a stretch to decrease the risk of injury. When performing a program of hamstring stretching with limited trunk movement, improvement in spinal curvatures have been noted with improved straight leg raise values and decreased thoracic kyphosis.⁴

Multiple Assessments

Consider all options for testing when assessing trunk and lower extremity mobility with your patients. The best method is not using one or two tests for your full assessment but using a cluster of examination measurements to get a full idea of your patient’s movement. This can be a great segue into providing your patient with a comprehensive home exercise program to assist with improving healthy mobility and preventing future injury.