Original Editor - Tyler Shultz
The Thomas Test (also known as Iliacus Test or Iliopsoas Test) is used to measure the flexibility of the hip flexors, which includes the iliopsoas muscle group, the rectus femoris, pectineus, gracillis as well as the tensor fascia latae and the sartorius.
Clinically Relevant Anatomy
The hip joint is a diarthroidal ball and-socket style joint, formed from the head of the femur as it articulates with the acetabulum of the pelvis. It serves as the main connection between the lower extremity and the trunk, and typically works in a closed kinematic chain.
There are various muscles making up the hip flexor group being tested in the Thomas Test:
| Iliopsoas muscle group
|| Main Function
|| Additional movement|
| M. Iliopsoas
|| hip flexion
|| external rotation|
| M. Rectus Femoris
|| hip flexion
|| knee extension|
| M. Tensor Fascia Latae
|| hip flexion
|| internal rotation, abduction|
| M. Sartorius
|| hip flexion
|| knee flexion|
The patient should be supine on the examination table, maximally flex both knees, using both arms to ensure that the lumbar spine is flexed and flat on the table and avoids a posterior tilt of the pelvis.
The patient then lowers the tested limb toward the table, whilst the contralateral hip and knee is still held in maximal flexion to stabilize the pelvis and flatten out the lumbar lordosis. The length of the iliopsoas is measured by the angle of the hip flexion.
A modified version of the test is one in which the patient lies down on their back, at the very edge of the table, with both legs hanging freely. The patient must then flex their knee and pull it back to their chest as close as they can, using both arms while doing so. The other leg can hang down. The lumbar spine must remain flat and in contact with the table during the test. The physiotherapist controls the opposite leg to ensure that it maintains full contact with the table.
The Thomas test is negative when the subject's lower back and the sacrum is able to remain on the table. The hip can make a 10° posterior tilt or a 10° hip extension. The knee must be able to make a 90° flexion.
The test is positive when:
- Subject is unable to maintain their lower back and sacrum against the table
- Hip has a large posterior tilt or hip extension greater than 15°
- Knee unable to meet more than 80° flexion
The following structures may be considered during a positive test;
|Extended knee||Quadriceps, rectus femoris|
|Flexed hip||Psoas muscles|
|Abducted hip||Tensor Fascia Latae, ITB|
|Tibia lateral rotation||Biceps femoris|
Studies that test the reliability of the Thomas study are very limited.
One study has demonstrated that the modified Thomas test has a very good inter-rater reliability. Another has demonstrated that the modified Thomas test, has an average of only moderate levels of reliability. Further research is required to prove or to refute the reliability of the Thomas test.
Peeler et al., 2006 conducted a study examining the reliability of the Thomas test for assessing hip range. Their study calls into question the reliability of the technique when used to score ROM and iliopsoas muscle flexibility about the hip joint using both goniometer and pass/fail scoring methods.
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