Trauma or Injury: The most common cause of finger stiffness is a previous injury, such as a sprain, strain, or fracture, which can lead to stiffness due to inflammation, scarring, or improper healing.

Osteoarthritis: A common condition that can cause stiffness in the fingers, especially in older adults, due to wear and tear of the joints.
Rheumatoid Arthritis: An autoimmune disease that can cause inflammation and stiffness in the fingers, often affecting multiple joints.
Tendinitis: Inflammation of the tendons, which can cause stiffness and pain in the affected finger.
Trigger Finger: A condition where the tendon sheath becomes inflamed, causing the finger to catch or lock, leading to stiffness.

Infection (e.g., Osteomyelitis or Septic Arthritis): Although less common, infections can cause severe stiffness and pain in the finger, and prompt treatment is essential to prevent long-term damage.
Ganglion Cyst: A non-cancerous lump that can cause stiffness and pain in the finger, especially if it compresses a nerve or tendon.
Nerve Compression (e.g., Cubital Tunnel Syndrome): Compression of the ulnar nerve can cause stiffness, numbness, and tingling in the ring and little fingers, but can also affect the middle finger.

Scleroderma: A rare autoimmune disease that can cause thickening of the skin and stiffness in the fingers.
Ehlers-Danlos Syndrome: A genetic disorder that can cause hypermobile joints, including finger stiffness.
Psoriatic Arthritis: A type of arthritis that occurs in people with psoriasis, which can cause stiffness and pain in the fingers.
Gout: A type of arthritis that can cause sudden, severe stiffness and pain in the fingers, often accompanied by redness and swelling.