Hip Flexion Contracture in Transfemoral Amputees: Thomas Test and Prone Protocols
In short
Hip flexion contractures over 15 degrees force excessive lumbar lordosis and trigger knee buckling; daily prone positioning and contract-relax stretches prevent deformity.
In this guide (4 sections)
The Biomechanics of Post-Amputation Hip Flexion Contracture
Following above-knee amputation, patients naturally spend prolonged hours seated in wheelchairs or armchairs. The iliopsoas, rectus femoris, and tensor fasciae latae remain in a shortened position, while the transected hamstrings and disrupted adductor magnus cannot counter the shortening vector.
Even a mild 10 to 15 degree hip flexion contracture presents severe prosthetic hurdles. To stand erect, the amputee must hyperextend their lumbar spine, generating chronic low back pain. In prosthetic alignment, a flexed hip places the ground reaction force behind the prosthetic knee axis, triggering sudden knee collapse during stance.
Clinical Assessment: The Modified Thomas Test
| Severity Degree | Contracture Angle | Prosthetic Alignment Adjustment | Functional Gait Impact | |
|---|---|---|---|---|
| Mild Contracture | 5 to 15 degrees | Accommodated by pre-flexing socket 5 degrees past contracture | Mild lumbar lordosis; normal step length achievable | |
| Moderate Contracture | 16 to 25 degrees | Socket pre-flexed; anterior foot placement required | Noticeable short step on intact side; early heel rise on prosthetic side | |
| Severe Contracture | Greater than 25 degrees | Extremely difficult to align; unstable knee geometry | Significant back pain, high fall risk, inability to clear toe without vaulting |
Physiotherapy Management and Reversal Protocol
- Strict Prone Lying Schedule: Instruct the patient to lie flat on their stomach on a firm mattress for 30 minutes, 3 to 4 times every day; place a thin sandbag over the posterior pelvis if tolerated.
- Pillows Under Stump Strictly Prohibited: Educate nursing staff, caregivers, and patients that placing a pillow under the residual limb in bed directly causes hip flexion contractures and must never be permitted.
- Contract-Relax Hip Extensor Training: Perform active resisted gluteus maximus contractions in prone, pressing the residual limb down into the examination table against clinician resistance for 6 seconds, followed by 15 seconds of passive extension relaxation.
Frequently Asked Questions
Why did my doctor tell me never to place a pillow under my stump while lying in bed?
Elevating the residual limb on a pillow keeps your hip bent at a 20 to 30 degree angle. Within 2 to 3 weeks, your hip flexor muscles permanently shorten, making it impossible to stand upright in an artificial leg.
Can a tight hip prevent me from getting an artificial leg?
Yes. If a contracture exceeds 25 to 30 degrees, the artificial knee cannot achieve stable stance alignment without dangerous buckling. Physiotherapy must reduce the contracture before fitting.
How long does it take to stretch out a hip contracture?
Mild contractures under 15 degrees typically resolve within 3 to 6 weeks of disciplined prone lying and physiotherapy. Contractures present for months take considerably longer and require intensive manual mobilization.
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