**Core Concept**
The ilio-tibial tract (IT tract) is a fascial band extending from the iliac crest to the tibia, providing stability to the knee joint. Post-polio syndrome is characterized by progressive muscle weakness, atrophy, and contractures in individuals who have had poliomyelitis. Contractures in the IT tract can lead to knee joint deformity and limited mobility.

**Why the Correct Answer is Right**
In a post-polio case, ilio-tibial tract contracture is likely to result in a **tibial torsion**. This occurs due to the imbalance in muscle forces around the knee joint, leading to a varus deformity (inward angulation of the lower leg) and tibial torsion (a rotational deformity of the tibia). The IT tract contracture restricts the normal movement of the knee joint, causing the tibia to twist inward, leading to tibial torsion.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the post-polio syndrome or ilio-tibial tract contracture.
* **Option B:** Contracture of the IT tract is not typically associated with hip flexion contracture or limited hip mobility.
* **Option C:** This option is not a direct consequence of ilio-tibial tract contracture in post-polio syndrome.

**Clinical Pearl / High-Yield Fact**
Tibial torsion in a post-polio case can be managed with orthotics, physical therapy, and, in severe cases, surgical intervention to correct the deformity and improve knee joint mobility.

**Correct Answer: D. Tibial torsion**