Positioning the Pelvis: addressing Posterior Pelvic Tilt
The dreaded posterior pelvic tilt. The bane of seating clinics everywhere. What is it and how can we correct this issue? The position of the pelvis determines the position of the trunk and lower extremities. Providing as neutral a pelvic position as possible improves overall posture, stability, and function.
What is a Posterior Pelvic Tilt?
A Posterior Pelvic Tilt (PPT) occurs when the top of the pelvis is tipped posteriorly. This leads to flexion of the spine, including the neck. This is sometimes referred to as sacral sitting because weight bearing may actually occur on the sacrum, rather than on the ischial tuberosities, creating a risk for pressure injuries.
What Causes a Posterior Pelvic Tilt?
Strategies to address PPT depend on the cause, so it is critical to determine why a client is moving into this position. The Mat Assessment can help us identify the culprit.
- Low tone or muscle weakness in the trunk can lead to PPT as the body collapses under gravity.
- Range of motion limitations in the hamstrings may pull the pelvis into PPT, particularly if the feet are pulled forward.
- Range of motion limitations in hip flexion. Pushing the legs upward into flexion at the hip will push the pelvis back into PPT.
- Seat depth, if too long for the client, will not allow the pelvis to move back enough on the seating surface to contact the back which provides posterior pelvic support.
- Extension – the client may actively extend, leading to a loss of position.
So, What can we do?
If the cause is low tone, weakness, or extension, it is critical to provide adequate posterior support of the pelvis. Firm support is required. Many backs employ a bi-angular shape to provide adequate postural support to the posterior pelvis while allowing for trunk extension.
The hamstrings cross both the pelvis and the knee, making these a multi-joint muscle. If tight hamstrings are pulling the pelvic into a PPT, opening the thigh to trunk (seat to back) angle can relieve the pull at the pelvis and decreasing the thigh to calf angle can relieve the pull at the knee
If the set depth is too long, provide the appropriate depth for the individual’s hip and knee flexion. If the client is growing, strategies are available to provide growth without compromising posture.
An over-long seat depth will pull the pelvis into a posterior pelvic tilt.
If hip flexion is limited, the seat to back angle needs to be opened to accommodate the available range of motion.
If the client has range limitations into hip flexion, flexion past available range will lead to posterior pelvic tilt.
For clients who slide forward on the seat or actively push into extension, posterior support to the pelvis is critical to prevent posterior rotation of the pelvis. However, we also need to block rotation at the front of the pelvis, and this is accomplished by limiting forward movement of the ischial tuberosities (ITs) through seating contours and an appropriately angled pelvic positioning belt. Many off the shelf cushions include an anti-thrust design to limit forward movement of the ITs.
A pelvic positioning belt placed at a 60 degree angle works with the cushion shape to prevent forward movement.
Goals Correcting a posterior pelvic tilt provides neutral alignment of the pelvis to support the anatomical curvatures of the spine, promote weightbearing on the ischial tuberosities to reduce pressure injury risk, and provide optimal alignment and stability for function. These goals can also be used as funding justifications in our documentation.
Michelle L. Lange, OTR/L, ABDA, ATP/SMS