Line joining ant. sup iliac spine to ischial tuberosity and passes a greater trochanter
**Core Concept**
The question requires knowledge of the surface anatomy of the lower extremities and pelvis. The line joining the anterior superior iliac spine (ASIS) to the ischial tuberosity and passing over the greater trochanter is a significant anatomical landmark in orthopedics and surgery.
**Why the Correct Answer is Right**
The line in question is known as the "modified Thomas test" or the "longitudinal axis of the femur." It represents the alignment of the femur in the sagittal plane. This line is significant in orthopedic examination, as it helps in assessing the hip joint's range of motion and identifying potential problems such as hip flexion contracture or femoral anteversion. The greater trochanter, a bony prominence on the lateral aspect of the femur, serves as a key landmark for this line.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the line joining the ASIS to the ischial tuberosity and passing over the greater trochanter.
* **Option B:** This option is incorrect because it does not specify the anatomical landmarks involved in the line.
* **Option C:** This option is incorrect because it does not accurately describe the anatomical relationship between the ASIS, ischial tuberosity, and greater trochanter.
**Clinical Pearl / High-Yield Fact**
When performing a physical examination of the hip joint, drawing an imaginary line from the ASIS to the ischial tuberosity and passing over the greater trochanter can help in assessing the hip's range of motion and identifying potential problems.
**Correct Answer: C. Sciatic nerve passes under the piriformis muscle and is located along this line.**