Carpal Tunnel Syndrome: This condition is a common cause of chronic unilateral hand pain, especially in individuals who perform repetitive tasks with their hands. Symptoms include numbness, tingling, and pain in the hand, particularly in the thumb, index, and middle fingers.

Tendinitis or Tenosynovitis: Inflammation of the tendons or their surrounding sheaths can cause pain and stiffness in the hand, often related to overuse or repetitive strain.
Ganglion Cyst: A lump or mass that forms on the wrist or hand, which can cause pain, especially if it presses on a nerve.
Osteoarthritis: Wear and tear on the joints of the hand can lead to chronic pain, stiffness, and limited mobility.
Repetitive Strain Injury (RSI): A broad term that encompasses various conditions caused by repetitive motion, leading to pain and discomfort in the hand and wrist.

Infection (e.g., Osteomyelitis, Septic Arthritis): Although less common, infections in the hand or wrist can cause severe pain and have serious consequences if not promptly treated.
Tumor (Benign or Malignant): Rarely, chronic hand pain can be a symptom of a tumor, which would require immediate medical attention.
Complex Regional Pain Syndrome (CRPS): A condition characterized by intense burning or aching pain in the hand or arm, often following an injury or trauma, which can have severe and lasting effects if not properly managed.

Sarcoidosis: A systemic disease that can cause inflammation and pain in various parts of the body, including the hands, though this is a less common presentation.
Gout: Typically affects the feet but can occasionally cause arthritis and pain in the hands.
Ehlers-Danlos Syndrome: A group of disorders that affect connective tissues, which can lead to joint hypermobility and chronic pain, including in the hands.
Thoracic Outlet Syndrome: Compression of the nerves or blood vessels that pass into the arm can cause pain in the hand, though this is more commonly associated with neck and shoulder pain.