Musculoskeletal strain: This is often the most common cause of neck stiffness and pain, resulting from overuse, poor posture, or direct injury to the muscles and ligaments in the neck.

Cervical spondylosis: A condition involving wear and tear on the disks in the neck, which can cause stiffness and pain.
Herniated cervical disk: When the soft inner gel of the disk leaks out through a tear or crack, it can irritate nearby nerves and cause pain and stiffness.
Whiplash: An injury to the neck caused by a sudden movement of the head forwards, backwards, or sideways, often occurring after a car accident.
Torticollis: A condition where the neck muscles become twisted, leading to stiffness and pain, often presenting with an abnormal head or neck position.

Meningitis: An infection of the protective membranes covering the brain and spinal cord, which can present with neck stiffness, fever, and headache. Early diagnosis is crucial for effective treatment.
Subarachnoid hemorrhage: Bleeding into the space between the brain and the tissue that covers it, often due to an aneurysm rupture, presenting with sudden severe headache and neck stiffness.
Cervical spine fracture: A break in one of the cervical vertebrae, which can be life-threatening if not promptly diagnosed and treated, especially if it compromises the spinal cord.
Spinal epidural abscess: A collection of pus that forms in the space outside the sac that contains the spinal fluid, which can compress the spinal cord and cause severe neurological deficits if not treated promptly.

Rheumatoid arthritis: An autoimmune disorder that can cause inflammation and pain in the joints, including those in the neck, though neck involvement is less common.
Ankylosing spondylitis: A type of arthritis that primarily affects the spine, although it can also affect other joints, causing chronic pain and stiffness.
Cervical spine infection (e.g., osteomyelitis, discitis): Infections of the cervical spine bones or disks, which are rare but can cause significant morbidity if not properly treated.
Neck tumors: Both benign and malignant tumors can occur in the neck, causing stiffness and pain, though they are less common causes of these symptoms.