**Core Concept**
The medial meniscus of the knee joint is injured more frequently than the lateral meniscus due to its anatomical position and the resulting mechanical stresses. The medial meniscus is a C-shaped fibrocartilaginous structure located on the medial (inner) aspect of the knee joint, whereas the lateral meniscus is situated on the lateral (outer) aspect.

**Why the Correct Answer is Right**
The medial meniscus is relatively more constrained and subjected to greater valgus stress (a force that pushes the knee inward) due to its attachment to the medial collateral ligament and the deep portion of the medial meniscus being in close proximity to the medial collateral ligament. This results in increased contact stress and a higher likelihood of injury to the medial meniscus. In contrast, the lateral meniscus is relatively more mobile and experiences less valgus stress.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the lateral meniscus is not more constrained or subjected to greater valgus stress than the medial meniscus. In fact, it is the opposite.
**Option B:** This option is incorrect because the medial meniscus is not less mobile than the lateral meniscus; rather, it is more constrained and experiences greater valgus stress.
**Option C:** This option is incorrect because the medial meniscus is not less commonly injured than the lateral meniscus; in fact, it is more frequently injured.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the medial meniscus is more commonly injured due to its anatomical position and the resulting mechanical stresses, which can lead to increased contact stress and a higher likelihood of injury.

**Correct Answer: C. The medial meniscus is relatively more constrained.**