Thomas Test


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.[1]

Impaired range of motion of the hip may be an underlying cause to other conditions such as patellofemoral pain syndrome [2], lower back pain[3], osteoarthritis and rheumatoid arthritis[4].

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


Thomas Test video provided by Clinically Relevant

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.[1]

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.[5] The length of the iliopsoas is measured by the angle of the hip flexion.[6]

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.[6] The lumbar spine must remain flat and in contact with the table during the test.[1] 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.[7]

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;

Sign Structures affected
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.[8] Another has demonstrated that the modified Thomas test, has an average of only moderate levels of reliability.[9] 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.[10]


  1. 1.0 1.1 1.2 Harvey D. Assessment of the flexibility of elite athletes using the modified Thomas test. Br J Sports Med 1998 32: 68-70.
  2. Tyler TF, Nicholas SJ, Mullaney MJ, McHugh MP. The role of hip muscle function in the treatment of patellofemoral pain syndrome. Am J Sports Med. 2006 Apr; 34(4):630-6.
  3. G. Marrè-Brunenghi, R. Camoriano, M. Valle and S. Boero; The psoas muscle as cause of low back pain in infantile cerebral palsy; J Orthop Traumatol. 2008 March; 9(1): 43–47.
  4. John Crawford Adams, David L. Hamblen; Outline of orthopaedics; Churchill Livingstone, 13th edition, 2001 - 459 pagina's
  5. Jeff G. Konin, Holly Brader. Lumbar Spine Special tests for orthopedic examination. Third edition. USA. Slack Incorporated. 2006.p170
  6. 6.0 6.1 Jeffrey Tucker, DC, DACRB. The Psoas and Iliacus: Functional Testing. Dynamic Chiropractic. September 24, 2007, Vol. 25, Issue 20.
  7. Mark McKean. Postural Screening using the Thomas Test – Part 1. Pistol Australia. P11-13.
  8. Belinda J Gabbea, Kim L Bennellb, Henry Wajswelnerc, Caroline F Fincha; Reliability of common lower extremity musculoskeletal screening tests; Physical Therapy in Sport, Volume 5, Issue 2, Pages 90-97 (May 2004).
  9. Phyllis A Clapis, PT, DHSc, OCS1, Susan Mercik Davis and Ross Otto Davis; Reliability of inclinometer and goniometric measurements of hip extension flexibility using the modified Thomas test; Physiotherapy Theory and Practice ; 2008, Vol. 24, No. 2 , Pages 135-141
  10. Peeler J, Anderson JE. Reliability of the Thomas test for assessing range of motion about the hip. Physical Therapy in Sport. 2007 Feb 1;8(1):14-21.