Differential Diagnosis for Jamie's Condition

Single Most Likely Diagnosis

• Mallet Finger: This condition is characterized by the inability to extend the distal interphalangeal (DIP) joint due to a rupture of the extensor tendon, often caused by a sudden, forceful flexion of the finger, such as when an object (like a ball) strikes the tip of the finger. The presentation of severe flexion, inability to extend, and pain on palpation of the DIP joint aligns closely with mallet finger.

Other Likely Diagnoses

• Volar Plate Injury: An injury to the volar plate, a ligament that connects the phalanges in the finger, can cause pain and limited mobility, especially if it involves the DIP joint. However, the primary symptom of a volar plate injury is more likely to involve instability or pain with flexion rather than an inability to extend.
• Distal Interphalangeal Joint Dislocation: A dislocation of the DIP joint could cause severe pain, deformity, and limited mobility. The direction of the dislocation (dorsal or volar) would influence the presentation, with a dorsal dislocation potentially causing an inability to extend the joint.
• Flexor Tendon Injury: An injury to the flexor tendon, particularly at the level of the DIP joint, could lead to flexion deformity and pain. However, the primary complaint would more likely involve difficulty flexing the finger rather than extending it.

Do Not Miss Diagnoses

• Infection (e.g., Septic Arthritis): Although less likely given the context, an infection involving the DIP joint could present with pain, swelling, and limited mobility. Missing this diagnosis could lead to serious complications, including joint destruction and systemic infection.
• Fracture: A fracture of the distal phalanx, especially if it involves the joint (intra-articular), could cause significant pain, deformity, and limited mobility. Certain types of fractures, like those involving the base of the distal phalanx, might specifically impair extension.

Rare Diagnoses

• Tumor: A tumor affecting the bone, soft tissue, or tendon of the finger could cause pain and limited mobility. However, this would be a rare cause of acute inability to extend the DIP joint.
• Neurological Conditions: Certain neurological conditions affecting the hand, such as a peripheral nerve injury or a condition like camptodactyly (a congenital deformity), could potentially cause flexion deformity. However, these would be unusual causes of an acute presentation like Jamie's.