Okay, let's tackle this question. The question is about a fracture of the 5th metatarsal tuberosity due to forceful inversion of the foot. The student needs to identify which tendon's pull causes this.

First, I need to recall the anatomy of the foot. The 5th metatarsal is part of the foot's structure, and its tuberosity is a common fracture site. Forceful inversion would cause the foot to twist inward, which might stretch certain structures. The tuberosity is attached to specific tendons.

The peroneus brevis tendon runs along the lateral side of the foot and inserts into the 5th metatarsal. If the foot inverts forcefully, the peroneus brevis has to contract to evert the foot, which could lead to a fracture if the force is too great. The peroneus longus, on the other hand, inserts into the first metatarsal and medial cuneiform, so it's less likely involved here.

Other tendons like the tibialis anterior and posterior are more involved in dorsiflexion and plantarflexion, not inversion. The extensor digitorum longus might have some role, but not directly on the 5th metatarsal.

So the correct answer should be peroneus brevis. The other options don't have the right insertion points. The clinical pearl here is that avulsion fractures of the 5th metatarsal are often due to peroneus brevis, and this is a common sports injury. Students should remember the insertion points of these tendons to avoid confusion.

**Core Concept**
This question tests knowledge of foot anatomy and biomechanics, specifically the musculotendinous attachments responsible for 5th metatarsal tuberosity fractures during forceful inversion. The 5th metatarsal tuberosity is a common site for avulsion fractures due to tendon pull during extreme foot movements.

**Why the Correct Answer is Right**
The **peroneus brevis tendon** inserts directly into the lateral (5th) metatarsal tuberosity. During forceful inversion, the peroneus brevis contracts to evert the foot, creating a strong tensile force on its insertion. If this force exceeds the bone's strength, an avulsion fracture occurs. This mechanism is termed a **Jones fracture**, a classic injury in athletes. The peroneus brevis is distinct from the peroneus longus, which inserts more distally on the first metatarsal and medial cuneiform.

**Why Each Wrong Option is Incorrect**
**Option A:** *Tibialis anterior* – Inserts into the medial cuneiform and first metatarsal; involved in dorsiflexion, not lateral foot stress.
**Option B:** *Tibialis posterior* – Inserts into navicular and cuneiforms; stabilizes the medial arch, not the lateral foot.
**Option C:** *Extensor digitorum longus* – Extends toes and dorsiflexes the foot; no direct attachment to the 5th metatarsal.

**Clinical Pearl / High-Yield Fact**
Remember the **"Jones fracture"** mnemonic: *Peroneus brevis pulls on the 5th metatarsal during inversion, causing a transverse fracture at the tuberosity.* Distinguish

✓ Correct Answer: B. Peroneus brevius