What is a joint mouse?

What is a joint mouse?

• A. A free joint body of cartilage or bone
• B. A calcified lesion on bone
• C. A tear in the meniscus
• D. A fracture of the tibial plateau

Answer: (A)

A joint mouse is a loose body inside a joint, typically a fragment of cartilage or bone that has become detached and floats within the synovial space. This free-floating piece can move with the joint and may cause mechanical symptoms such as intermittent locking, catching, reduced range of motion, or pain during movement. They often originate from osteochondral fragments or degenerative changes in the joint, and are often found on imaging or during arthroscopy as a discrete, non-fixed body within the joint. This distinguishes them from a calcified lesion fixed to bone, a tear of the meniscus, or a fracture of the tibial plateau, none of which describe a free-floating intra-articular fragment.

A joint mouse is a loose body inside a joint, typically a fragment of cartilage or bone that has become detached and floats within the synovial space. This free-floating piece can move with the joint and may cause mechanical symptoms such as intermittent locking, catching, reduced range of motion, or pain during movement. They often originate from osteochondral fragments or degenerative changes in the joint, and are often found on imaging or during arthroscopy as a discrete, non-fixed body within the joint. This distinguishes them from a calcified lesion fixed to bone, a tear of the meniscus, or a fracture of the tibial plateau, none of which describe a free-floating intra-articular fragment.