Dupuytren's Contracture: A condition characterized by the thickening of the palmar fascia, leading to flexion deformity of the fingers, particularly affecting the dip (distal interphalangeal) joints. It's a common condition that matches the described symptomatology.

Trauma or Injury: Direct injury to the fingers can cause flexion deformity due to fracture, dislocation, or soft tissue damage around the dip joint.
Rheumatoid Arthritis: Although it more commonly affects the proximal interphalangeal (PIP) joints, rheumatoid arthritis can also cause deformities in the dip joints, leading to flexion.
Osteoarthritis: Especially in the context of nodal osteoarthritis (Bouchard's and Heberden's nodes), which can lead to flexion deformity of the dip joints.

Infection (Septic Arthritis): An infection within the joint can cause severe pain, swelling, and deformity. Although less common, it's critical to diagnose and treat promptly to avoid permanent damage.
Tendon Rupture: A rupture of the extensor tendon can lead to an inability to extend the finger, resulting in a flexion deformity. This condition requires urgent surgical intervention.
Neurological Conditions (e.g., Stroke, Peripheral Neuropathy): Certain neurological conditions can lead to muscle imbalances or weakness, potentially causing flexion deformities of the fingers.

Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. It can lead to joint hypermobility and, in some cases, flexion deformities.
Scleroderma: A chronic disease characterized by deposition of collagen, leading to thickening and hardening of skin and connective tissue. It can cause flexion contractures of the fingers.
Camptodactyly: A rare congenital condition where the little finger is bent towards the palm, which can sometimes involve the dip joint.