Causes of Septic Arthritis

Different bacteria and viruses can infect a joint and usually are associated with a person's age, including the following:

• Staphylococci (a common bacteria that often causes skin infections), Haemophilus influenzae (a bacteria that can infect the larynx, trachea, and bronchi), and gram-negative bacilli (a group of bacteria, including Escherichia coli, or E. coli) are usually associated with young children and infants.
• Gonococci (the bacteria that causes gonorrhea), staphylococci, and streptococci (a group of bacteria that can lead to a wide variety of diseases) are usually associated with older children and adults.
• Viruses, such as the human immunodeficiency virus (HIV), tend to infect the joints of people of all ages.