Thomas test

The Thomas test is named after the Welsh orthopedic surgeon Hugh Owen Thomas (1834–1891). Thomas is also known for the “Thomas splint,” used to immobilize fractures. The test was originally used to identify hip flexion contracture, in which the hip becomes fixed in a bent position.

Later, the modified Thomas test, which slightly changes the position and sequence, became widely used in exercise and rehabilitation settings. The person lies at the edge of a bed, hugs one knee toward the chest, and lets the other leg hang off the bed. It is commonly used in practice because it can be performed in a few minutes without special equipment.

This test assesses the flexibility of the muscles that cross the front of the hip. Three key muscles are involved.

• Iliopsoas: A deep muscle that runs from the lumbar spine to the inner side of the femur and plays the largest role in lifting the leg.
• Rectus femoris: One of the muscles at the front of the thigh, crossing both the hip and the knee.
• Tensor fasciae latae: A small muscle that runs from the outer side of the pelvis to the outside of the thigh.

Hugging one knee toward the chest naturally tilts the pelvis backward, while the opposite leg is lowered under gravity. The position of the lowered leg is then used to gauge the condition of these muscles.

1. Sit at the edge of a bed, then slowly lie down. Position the bottom of the buttocks at the edge of the bed. 2. Use both hands to hug one knee toward the chest so that the lower back rests lightly against the bed. 3. Relax the opposite leg and let it hang comfortably off the bed. 4. The examiner observes the height of the lowered thigh, the degree of knee flexion, and the direction the foot points. 5. Repeat on the other side and compare the two sides.

The findings are often interpreted as follows.

• If the thigh remains above the surface of the bed, the flexibility of the iliopsoas is examined.
• If the knee bends rather than remaining straight, the rectus femoris is examined.
• If the leg moves out to the side or the foot turns outward, the tensor fasciae latae is examined.

The person being tested usually feels a stretch at the front of the thigh or in the groin. This is not a test that requires enduring pain; the position is held comfortably with the muscles relaxed.

The angles or heights observed in this test are not direct measurements of the length of a single muscle. They also reflect how much the pelvis tilts, how far the lower back lifts off the bed, and how the weight of the leg is distributed. For this reason, the examiner takes care to keep the pelvis and lower back in a consistent position. Repeatedly observing the same person using the same method can help track changes over time.

There are also several ways to measure the angles, including visual assessment, measurement with a goniometer, and assessment using photographs. Results vary slightly depending on the method. Comparing the two sides under the same conditions and tracking later changes is therefore more helpful than relying on a single measurement.

• People who feel stiffness at the front of the thigh or in the groin after spending long periods sitting
• People who do activities involving repeated leg lifting, such as running, cycling, or soccer
• People who feel that their lower back arches forward excessively when standing
• People who want to check how much changes before and after stretching

You can try a similar movement on your own at the edge of a bed. Hug one knee toward your chest and notice whether the opposite leg lowers comfortably. If one side feels tighter than the other, you may also want to try a stretch that slowly lengthens the front of that hip. Checking whether your lower back lifts excessively off the bed can also help you see which way your pelvis is tilting.