Bone and joint damage from rapid pressure changes, often from diving or altitude.
Because your rating depends entirely on which body system was affected, the evidence that helps will match that system. For musculoskeletal residuals such as joint pain or arthritis, useful evidence includes X-rays, range-of-motion measurements from physical exams, and records of ongoing treatment. For vestibular or auditory residuals, audiology test results and balance assessments are relevant. For pulmonary residuals, breathing-function test results and pulmonary exam findings matter. For neurologic residuals such as those resembling a stroke, imaging studies, neurological exam findings, and records of cognitive or motor deficits are relevant. Across all body systems, statements from you or people who know you describing how your symptoms affect your ability to work, care for yourself, or carry out daily activities can help show the severity of your residuals at whatever rating level applies to your specific condition.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.