Is There a Cause of Inability to Extend the Fingers in a Patient With Rheumatoid Arthritis?

A 65-year-old woman with rheumatoid arthritis is unable to actively extend her index, middle, ring, and little fingers secondary to tendon rupture. The most likely cause of inability to extend the fingers in this patient is posterior interosseous nerve or PIN palsy. An MRI of the elbow may show Cinnovitis at the radiocapatellar joint, which can causePIN palsy.