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Thomas test hip flexion contracture procedure

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Here is a comprehensive account of the Thomas Test (Hugh Owen Thomas' Test):

Thomas Test

Aim / Purpose

The Thomas test is used to detect and measure fixed flexion deformity (FFD) of the hip joint. In the normal resting position, a patient with a hip flexion contracture compensates by exaggerating lumbar lordosis, which masks the true deformity. The test eliminates this compensation and reveals the actual degree of contracture.
  • Structures assessed: iliopsoas, and in the modified version also rectus femoris and tensor fasciae latae (TFL)

Procedure

  1. Position the patient supine on a firm, flat examination table.
  2. Flex the sound (unaffected) hip — bend the thigh toward the chest with the knee also flexed — until the lumbar lordosis is completely obliterated. This is confirmed by the examiner's hand being unable to be insinuated between the lumbar spine and the bed.
  3. Maintain this position (the patient may hold the flexed knee with both hands).
  4. Observe the affected (test) limb: Once the lordosis is eliminated, any hidden flexion contracture of the affected hip is unmasked and that limb will rise off the table.
  5. Measure the angle between the affected thigh and the horizontal surface of the table — this angle equals the degree of fixed flexion deformity.
Key principle: The sound thigh should be flexed only enough to eliminate the lordosis. Over-flexing will artificially exaggerate the apparent deformity of the affected hip.

Modified Thomas Test (Extended Version)

In the modified version:
  • The patient sits at the edge of the table, then lies back, bringing both knees to the chest.
  • The contralateral (normal) hip is held maximally flexed against the chest.
  • The test limb is allowed to hang freely off the table edge.
Observations from the hanging limb:
ObservationMuscle implicated
Thigh rises above horizontal (hip flexion)Iliopsoas tightness
Knee extends toward straight (>90°)Rectus femoris tightness
Hip abductsTFL / IT band tightness
Hip externally rotatesIT band restriction

Positive Sign

The test is positive when the affected (test) limb rises off the table and cannot remain flat, indicating a fixed flexion contracture of the hip.
  • The angle the thigh makes with the table surface = the angle of fixed flexion deformity
  • Common causes: osteoarthritis of hip, tuberculosis of hip, psoas abscess/spasm, prolonged bed rest in flexion

Negative Sign

The test is negative when the affected limb lies flat on the table, indicating no fixed flexion deformity — the hip has full extension range, and there is no iliopsoas contracture.

Visual Demonstration

Modified Thomas Test showing fixed flexion deformity of the right hip — right leg cannot fully straighten (arrow)
Figure: Modified Thomas's test. Fixed flexion deformity of the right hip is indicated by inability to fully straighten the right leg (arrow). — Bailey & Love's Short Practice of Surgery, 28th Ed., p. 510
Thomas test with biomechanical annotations showing thigh elevation (h) above table baseline indicating positive iliopsoas tightness
Figure: Thomas test with quantitative annotation — elevation of the thigh (h) above the table confirms a positive test.

Clinical Significance

FindingImplication
Positive Thomas testFixed flexion deformity of hip; psoas spasm or contracture
Angle of FFD measuredGuides surgical planning (e.g., psoas tenotomy for gait disorders)
Combined with other hip testsPart of complete hip examination in TB hip, OA, CDH
Sources: S Das — A Manual on Clinical Surgery, 13th Ed.; Bailey & Love's Short Practice of Surgery, 28th Ed., p. 510; Miller's Review of Orthopaedics, 9th Ed.
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