## Core Concept
Post-polio deformity (PPD) of the hip can result in various positional abnormalities due to muscle imbalance. The typical deformities are a result of weakness or paralysis of specific muscle groups around the hip. Understanding the function of hip muscles is crucial: the **gluteus maximus** primarily extends and externally rotates the hip, while the **hip flexors** (notably the iliopsoas) flex the hip.

## Why the Correct Answer is Right
In post-polio deformity, if there's weakness of the **gluteus maximus** and sometimes the hip flexors, the typical deformity that occurs is a **flexion**, **abduction**, and **external rotation** deformity. However, the classic and most common position associated with polio (or poliomyelitis) sequelae at the hip, due to the imbalance between the weakened gluteal muscles and relatively spared hip flexors, results in a characteristic posture. This posture is often described as **flexion**, **abduction**, and **external rotation**.

## Why Each Wrong Option is Incorrect
- **Option A:** This option might suggest a position but without specifics, it's hard to directly refute. Generally, any position not consistent with flexion, abduction, and external rotation would be incorrect based on the typical muscle imbalances seen.
- **Option B:** Similarly, without specifics, it's challenging to address directly. However, internal rotation or adduction would not align with the typical posture seen in PPD.
- **Option C:** This could potentially describe a position but again lacks specificity. A position that does not reflect the common deformity would be incorrect.

## Clinical Pearl / High-Yield Fact
A key clinical correlation to remember is that in polio sequelae, the **hip abductors** and **gluteus maximus** are commonly weakened, leading to a **Trendelenburg gait** and the characteristic deformity. Recognizing these deformities and understanding their implications on gait and function is crucial for rehabilitation planning.

## Correct Answer: C. flexion, abduction and external rotation.