Arthrofibrosis is a complication of injury or trauma to a joint. It can also be iatrogenic e.g. post knee surgeries. It consists of excessive scar tissue formation within the joint capsule, resulting in pain, stiffness, and swelling, that are greater than expected in the given clinical scenario.
It has been most extensively studied in the knee, where it is one of the leading causes of failure of total knee arthroplasty.
Arthrofibrosis can be diffuse or localized. The cyclops lesion is a specific manifestation of localized arthrofibrosis and consists of a focal rounded mass of fibrous/scar tissue which occurs anterior to a reconstructed ACL ligament.
Scar tissue appears as a low signal intensity lesion in T1 and T2 weighted images.