Inflammation of the superficial peroneal nerve, which may cause pain or numbness on the top of the foot.
Because the rating turns on how much function has been lost, medical records and physical examination findings that document the degree of weakness or impairment in the affected leg are the most directly relevant evidence. Findings showing how well or poorly you can evert your foot, along with nerve conduction studies or electromyography results that measure the extent of nerve damage, speak directly to whether the impairment is mild, moderate, or severe.
Records showing sensory loss alone are important because the regulation limits a purely sensory impairment to no higher than the moderate degree. Your own statements, and statements from people who see you daily, describing how foot weakness or sensory loss affects your ability to walk, work, or carry out daily activities help show the functional impact. Treatment records, notes from physical therapy, and any records of falls or difficulty with activities that require foot control all reflect how the condition affects you in practical terms.
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.