Immobility can lead to pressure sores,  particularly in bony areas, requiring precautions such as extra cushioning and turning in bed every two hours (in the acute setting) to relieve pressure. In the long term, people in wheelchairs must shift periodically to relieve pressure. Another complication is pain, including nociceptive pain (indication of potential or actual tissue damage) and neuropathic pain, when  nerves affected by damage convey erroneous pain signals in the absence of noxious stimuli. Spasticity, the uncontrollable tensing of muscles below the level of injury, occurs in 65–78% of chronic SCI. It results from lack of input from the brain that quells muscle responses to stretch reflexes. It can be treated with drugs and physical therapy. Spasticity increases the risk of contractures (shortening of muscles, tendons, or ligaments that result from lack of use of a limb); this problem can be prevented by moving the limb through its full range of motion multiple times a day. Another problem lack of mobility can cause is loss of bone density and changes in bone structure. Loss of bone density (bone demineralization), thought to be due to lack of input from weakened or paralysed muscles, can increase the risk of fractures. Conversely, a poorly understood phenomenon is the overgrowth of bone tissue in soft tissue areas,  called heterotopic ossification. It occurs below the level of injury, possibly as a result of inflammation, and happens to a clinically significant extent in 27% of people.
Spontaneous bleeding can occur within or outside of the protective membranes that line the cord, and intervertebral disks can herniate. Damage can result from dysfunction of the blood vessels, as in arteriovenous malformation, or when a blood clot becomes lodged in a blood vessel and cuts off blood supply to the cord. When systemic blood pressure drops, blood flow to the spinal cord may be reduced, potentially causing a loss of sensation and voluntary movement in the areas supplied by the affected level of the spinal cord. Congenital conditions and tumors that compress the cord can also cause SCI, as can vertebral spondylosis and ischemia. Multiple sclerosis is a disease that can damage the spinal cord, as can infectious or inflammatory conditions such as tuberculosis, herpes zoster or herpes simplex, meningitis, myelitis, and syphilis. Prevention
Vehicle-related SCI is prevented with measures including societal and individual efforts to reduce driving under the influence of drugs or alcohol, distracted driving, and drowsy driving. Other efforts include increasing road safety (such as marking hazards and adding lighting) and vehicle safety, both to prevent accidents (such as routine maintenance and antilock brakes) and to mitigate the damage of crashes (such as  head restraints, air bags, seat belts, and child safety seats). Falls can be prevented by making changes to the environment, such as nonslip materials and grab bars in bathtubs and showers, railings for stairs, child and safety gates for windows.