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A common sign of boutonniere deformity is characterized by extension of the proximal interphalangeal (PIP) joint combined with flexion of the distal interphalangeal (DIP) joint. This occurs due to a rupture or attenuation of the central slip of the extensor tendon at the PIP joint, which disrupts the normal function of the extensor mechanism. As a result, the PIP joint cannot fully extend, leading to its characteristic appearance of being bent, while the DIP joint often appears flexed due to the imbalance created by the affected tendons.

This presentation is essential for diagnosis and understanding the biomechanics involved in boutonniere deformity, which often results from trauma or conditions like rheumatoid arthritis. Recognizing this typical pattern helps healthcare providers devise appropriate interventions, such as splinting or surgery, to restore function and alignment of the affected digit.