## **Core Concept**
The **tibialis posterior muscle** is one of the muscles in the posterior compartment of the leg. It plays a crucial role in supporting the medial arch of the foot and in inversion and plantarflexion movements. The muscle's innervation is critical for its function.

## **Why the Correct Answer is Right**
The **tibialis posterior muscle** is supplied by the **tibial nerve**. The tibial nerve is a branch of the sciatic nerve and provides motor innervation to several muscles in the posterior thigh and leg, including the tibialis posterior. This nerve is responsible for the muscle's control over foot movements.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The **common peroneal nerve** primarily supplies muscles involved in foot eversion and toe movements, not the tibialis posterior.
* **Option B:** The **superficial peroneal nerve** mainly innervates the muscles of the lateral compartment of the leg, which are involved in foot eversion.
* **Option C:** The **deep peroneal nerve** supplies muscles in the anterior compartment of the leg, which are involved in foot dorsiflexion and toe extension.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation is that damage to the **tibial nerve**, such as in **tarsal tunnel syndrome**, can affect the function of the tibialis posterior muscle, leading to difficulties with foot inversion and support of the medial arch.

## **Correct Answer:** D. Tibial nerve.