Thomas Test: What It Is and How It Works

The Thomas test is a widely used orthopedic assessment that helps physical therapists evaluate hip flexor flexibility and identify potential musculoskeletal dysfunction. Named after Dr. Hugh Owen Thomas, this test remains relevant in clinical practice for its simplicity and clinical utility in evaluating conditions such as iliopsoas tightness, rectus femoris restriction, and hip joint abnormalities.

This article will review the purpose of the Thomas test, how to perform it correctly, what the results indicate, and how to apply the findings in clinical decision-making. A practical example is also included to help apply the technique in real-world practice.

What Is the Thomas Test?

The Thomas test is used to assess hip flexor muscle length, particularly focusing on the iliopsoas and rectus femoris muscles. Tightness in these muscles can contribute to lower back pain, postural deviations, and movement impairments.

The test is performed with the patient supine on a table. The patient brings one knee to the chest, allowing the other leg to hang off the edge. The clinician then observes the position of the extended leg to assess the length of the hip flexors.

The Thomas test is helpful in identifying:

• Iliopsoas tightness (hip remains flexed)

• Rectus femoris tightness (knee extends when hip is extended)

• Tensor fasciae latae or iliotibial band involvement (lateral deviation of the leg)

Understanding which structure is contributing to the limitation allows for more targeted intervention strategies.

Performing the Thomas Test

To obtain reliable results, clinicians should follow a standardized approach when performing the Thomas test.

Step-by-Step Instructions:

1. Positioning the patient: Have the patient lie supine on an examination table, close to the edge with legs hanging off.

2. Flexion of the opposite hip: Instruct the patient to pull one knee toward their chest and hold it with both hands. This action flattens the lumbar spine against the table, reducing anterior pelvic tilt.

3. Observation: With the opposite leg relaxed and extended off the table, observe the hip and knee position of the lowered leg.

Key observations:

• If the thigh of the lowered leg does not contact the table, iliopsoas tightness may be present.

• If the knee of the extended leg is significantly extended (greater than 90°), this may indicate rectus femoris tightness.

• If the leg abducts or externally rotates, involvement of the tensor fasciae latae or iliotibial band may be suspected.

Tip: Stabilize the pelvis and lumbar spine to prevent compensatory movements that could skew the results.

Interpreting Test Results

Proper interpretation of the Thomas test can help guide treatment planning, particularly when addressing posture, gait abnormalities, or lower back discomfort.

Clinicians should interpret findings within the context of the patient’s history, symptoms, and functional presentation. Bilateral testing is advised to compare sides.

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Example: Using the Thomas Test in Practice

Case scenario: A 45-year-old patient presents with anterior pelvic tilt, limited hip extension, and reports discomfort in the lower back during prolonged standing.

Application of the Thomas Test:

During the evaluation, the patient lies supine and flexes the right hip. The left thigh remains elevated above the table, and the knee extends to 100°. The leg also drifts slightly into abduction.

Interpretation:

• The elevated thigh suggests iliopsoas tightness.

• Knee extension beyond 90° indicates rectus femoris involvement.

• Abduction may point to tightness in the tensor fasciae latae.

Next Steps:

A tailored intervention plan may include:

• Manual therapy techniques to address soft tissue tightness

• Static and dynamic stretching for hip flexors

• Strengthening of the gluteus maximus and core musculature to improve pelvic alignment

• Postural re-education

This example demonstrates how the Thomas test can be used to assess contributing factors and inform a treatment strategy.

Limitations and Considerations

While the Thomas test is a useful tool, clinicians should be mindful of its limitations:

• False positives can occur if the lumbar spine is not stabilized or if the patient compensates with pelvic movement.

• The test does not isolate individual structures with complete specificity; overlapping muscle involvement is common.

• The presence of hip pathology, such as femoroacetabular impingement or labral tears, may alter test outcomes.

Clinical interpretation should always be made in conjunction with functional assessments and the patient’s history.

The Thomas test remains a practical orthopedic assessment for evaluating hip flexor flexibility. When performed and interpreted correctly, it can guide clinical decision-making in addressing postural issues, muscle imbalances, and movement dysfunction. By identifying the presence and severity of soft tissue restrictions, physical therapists can design more specific and functional treatment plans that improve patient outcomes.

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References

1. Kendall FP, McCreary EK, Provance PG, Rodgers MM, Romani WA. Muscles: Testing and Function, with Posture and Pain. Lippincott Williams & Wilkins; 2005.

2. National Library of Medicine. Iliopsoas muscle: function and clinical relevance. https://www.ncbi.nlm.nih.gov/books/NBK537032/