Hip flexion is necessary to complete a squat, forward bend, or even initiate the swing phase of gait. Whether the movement is open-chain or closed-chain, proper timing and activation of the hip flexors as well as disassociation of the lumbopelvic region is essential. Normal hip flexion active range of motion should be ~120 degrees. Due to prolonged sitting and chronic lumbar flexion posturing, many individuals lack adequate hip flexion. As a compensatory strategy, these people will move into early lumbar flexion when attempting hip movements.
When assessing hip flexion in the clinic, first I have the patient perform the movement without any cueing (R picture above). During this assessment, I look to see if the individual can disassociate the low back from the hips. As one can see, this person does not perform an isolated movement. As he pulls his femurs towards his chest, he rolls off his sacrum into a posterior pelvic tilt. The right image portrays both hip flexion and lumbar flexion. The left picture demonstrates his actual hip flexion range of motion. This range of motion is significantly less than the motion depicted on the R image. From a subjective complaint, he also reports a pinching pain in the anterior hip with this movement. The movement has shifted from appearing functional to very dysfunctional simply by cueing the position of the tailbone.
Identifying movement compensations is a topic I discuss frequently on The Movement Corner. In physical therapy school, we learn about kinesiology and regional interdependence, but we do not spend enough time viewing dysfunctional movement patterns. We know the body is one connected unit, yet we often forget this concept when prescribing exercises or looking at natural movement patterns. Identifying these dysfunctions will make you a more efficient clinician.
-Jim Heafner PT, DPT, OCS