Locking of knee joint can be caused by -a) Osgood shalterb) Loose body in knee jointc) Tuberculosis of kneed) Medial meniscal partial tear

**Core Concept**
Locking of knee joint occurs when a fragment of bone or cartilage becomes wedged between the articulating surfaces of the femur and tibia, preventing the knee from extending fully. This condition is often associated with degenerative joint disease, trauma, or inflammatory processes.

**Why the Correct Answer is Right**
A loose body in the knee joint can cause locking due to the mechanical obstruction it creates. When a fragment of bone or cartilage becomes dislodged, it can become trapped between the femur and tibia, preventing the knee from extending. This is a common cause of locking in the knee joint, particularly in older adults with osteoarthritis or after a traumatic injury.

**Why Each Wrong Option is Incorrect**
* **Option A:** Osgood-Schlatter disease primarily affects the tibial tubercle and is characterized by inflammation of the patellar tendon, leading to pain and swelling in the region. It does not typically cause locking of the knee joint.
* **Option B:** While tuberculosis of the knee can cause severe destruction of the joint, it is more commonly associated with pain, stiffness, and swelling rather than locking.
* **Option C:** A medial meniscal partial tear can cause pain, stiffness, and clicking sensations in the knee, but it is not typically associated with locking of the knee joint.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with knee locking, it is essential to consider the possibility of a loose body in the joint, particularly in the context of trauma, degenerative joint disease, or inflammatory processes.

**Correct Answer:** B. Loose body in knee joint