## **Core Concept**
Fixed flexion deformity of the hip is a condition where there is a permanent flexion contracture at the hip joint, leading to a decreased range of motion. This condition can result from various causes, including hip diseases, neurological disorders, or prolonged immobilization. The assessment of this deformity is crucial for diagnosing and planning the treatment.

## **Why the Correct Answer is Right**
The Thomas test, also known as the flexion test, is specifically designed to assess for fixed flexion deformity of the hip. In this test, the patient lies supine on an examination table and brings one knee towards the chest. The other leg, which is being tested, is allowed to fall into extension. If there is a fixed flexion deformity, the angle between the thigh and the table (or the extended leg) will be measurable, indicating the degree of deformity. This test effectively isolates and quantifies the flexion contracture.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, without a specific test mentioned, it's hard to directly refute, but commonly, tests like the straight leg raise are not specific for fixed flexion deformity.
- **Option B:** This option might refer to another orthopedic test, but without specifics, it's hard to directly address. However, tests like the FABER (Flexion, Abduction, and External Rotation) test are more related to assessing for hip or lumbar spine issues but not specifically for fixed flexion deformity.
- **Option C:** Similarly, this could refer to a variety of tests but is not recognized as a standard test for fixed flexion deformity of the hip.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the Thomas test can also be used to assess for flexion contractures in other joints, but it's most commonly associated with evaluating the hip. A positive test is indicated by a measurable angle of flexion that the hip cannot extend beyond, which helps in quantifying the deformity.

## **Correct Answer:** . Thomas test.