Flexor of lumbar spine is/are -a) Erector spineb) External oblique musclec) Internal oblique muscled) Rectus abdominise) Psoas major

## **Core Concept**
The question tests knowledge of muscles acting on the lumbar spine, specifically focusing on those responsible for flexion. Flexion of the lumbar spine involves movement of the spine in an anterior direction, effectively decreasing the angle between the front of the pelvis and the ribcage.

## **Why the Correct Answer is Right**
The correct answer involves identifying the muscles that primarily facilitate lumbar spine flexion.
- **Psoas major** is a key flexor of the lumbar spine. It originates from the lumbar vertebrae and inserts into the lesser trochanter of the femur, making it a primary flexor.
- **Rectus abdominis** also plays a significant role in lumbar spine flexion by contracting and pulling the pelvis towards the ribcage.
- **Internal oblique** and **external oblique muscles** contribute to lumbar spine rotation and lateral flexion but can also assist in flexion when acting bilaterally.

## **Why Each Wrong Option is Incorrect**
- **Option A: Erector spinae** - This group of muscles (including iliopsoas is not part of erector spinae, but rather a separate muscle; the actual components are: iliocostalis, longissimus, and spinalis) is primarily responsible for extension of the spine, not flexion.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation is that weakness in lumbar spine flexors, such as the **Psoas major** and **Rectus abdominis**, can lead to difficulties in activities like getting up from a lying position or maintaining posture.

## **Correct Answer:** D. psoas major, rectus abdominis, internal oblique, external oblique.