**Core Concept**
The comfort position for a distended knee joint is determined by the most effective alignment of the femur and tibia to reduce pain and discomfort. The goal is to minimize strain on the medial and lateral collateral ligaments, as well as the cruciate ligaments.

**Why the Correct Answer is Right**
The most comfortable position for a distended knee joint is flexion, specifically with the knee bent at an angle of approximately 20-30 degrees. This position allows the femur to move posteriorly and the tibia to move anteriorly, thereby reducing tension on the medial and lateral collateral ligaments. Additionally, flexion helps to decrease the pressure on the patellofemoral joint, providing relief from pain and discomfort.

**Why Each Wrong Option is Incorrect**
**Option A:** Extension, or straightening, of the knee joint would increase tension on the medial and lateral collateral ligaments, making it an uncomfortable position for a distended knee.
**Option B:** Full flexion, such as seen in a squatting position, may not provide adequate relief from pain and discomfort, as it can increase pressure on the patellofemoral joint.
**Option C:** A position with excessive external rotation of the tibia, such as seen in a valgus deformity, would put additional stress on the lateral collateral ligament, making it an uncomfortable position.

**Clinical Pearl / High-Yield Fact**
When managing a patient with a distended knee joint, it's essential to remember that the most comfortable position is one that allows for flexion and reduces tension on the collateral ligaments. This can be achieved by positioning the knee at 20-30 degrees of flexion.

**Correct Answer:** C.