Triple deformity of knee joint seen in :
**Core Concept**
The triple deformity of the knee joint refers to a combination of flexion, posterior subluxation, and external rotation deformities. This complex deformity is commonly seen in conditions that affect the knee joint, such as osteoarthritis, rheumatoid arthritis, or trauma.
**Why the Correct Answer is Right**
The triple deformity occurs due to the loss of function and integrity of the knee joint structures, including the ligaments and muscles. In particular, the posterior cruciate ligament (PCL) plays a crucial role in maintaining the normal alignment and stability of the knee joint. When the PCL is damaged or torn, the knee joint can subluxate posteriorly, leading to a flexion deformity. Additionally, the external rotation deformity occurs due to the imbalance of the surrounding muscles and ligaments.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically describe the triple deformity of the knee joint.
**Option B:** This option is incorrect because it refers to a different type of deformity, such as a valgus deformity, which is characterized by a deviation of the knee joint laterally.
**Clinical Pearl / High-Yield Fact**
The triple deformity of the knee joint is often associated with a PCL injury, and a thorough examination of the knee joint, including the PCL, is essential for accurate diagnosis and management.
**Correct Answer: C.**