**Core Concept**
The knee joint's stability and movement are primarily governed by the interaction between the femur (thigh bone), tibia (shin bone), and the surrounding ligaments and muscles. When a person moves from a flexed to an extended position, various mechanical forces come into play, affecting the joint's stability.

**Why the Correct Answer is Right**
When the knee is fully extended from a 90-degree flexed position, the posterior cruciate ligament (PCL) is put under tension. The PCL, along with the anterior cruciate ligament (ACL), is a critical stabilizer of the knee joint. However, in this scenario, the PCL is the primary stabilizer as the ACL is relaxed in extension. The PCL prevents excessive posterior translation of the tibia, thereby maintaining knee joint stability.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect because it doesn't specify the role of the PCL in knee joint stability during extension. Without mentioning the PCL, it's hard to determine its relevance.

**Option B:** This option might be incorrect because it doesn't provide a clear explanation of the mechanical forces at play when the knee is extended. Knee joint stability is a multifactorial process involving ligaments, muscles, and bones.

**Option C:** This option is likely incorrect because it doesn't address the specific scenario of knee extension. The relationship between the menisci and knee joint stability is complex and can vary depending on the position of the knee.

**Option D:** This option is likely incorrect because it doesn't specify the PCL's role in knee joint stability during extension. Without mentioning the PCL, it's hard to determine its relevance.

**Clinical Pearl / High-Yield Fact**
The PCL is often referred to as the "silent ligament" because it's less commonly injured than the ACL. However, PCL injuries can still lead to significant knee joint instability and should be carefully assessed in patients with knee pain or instability.

**Correct Answer: C. The posterior cruciate ligament (PCL) will be put under tension.**