During the Thomas Test, if the knee angle is not 90 degrees, what does that indicate?

• A. Tightness of Hamstrings
• B. Tightness of Rectus Femoris
• C. Tightness of Iliopsoas
• D. Tightness of Tensor Fasciae Latae

Answer: (B)

The Thomas test checks how hip flexors limit motion, and it helps tell apart the muscles that cross both the hip and knee from those that don’t. When you flex the hip to about 90 degrees by bringing the knee to the chest, a normal, length–matched rectus femoris should allow the knee to move toward the expected angle. If the knee angle is not 90 degrees—that is, the knee stays noticeably more flexed than the expected position—the rectus femoris is tight. Since rectus femoris crosses both joints, a tight rectus femoris prevents the knee from fully lengthening as the hip is flexed, leading to that non–90-degree knee angle. By contrast, signs of iliopsoas tightness show up as the thigh lifting off the table rather than simply a knee that can’t reach the 90-degree position.