Osteomyelitis is a serious bone infection that occurs when bacteria or fungi invade the bone tissue, causing inflammation and potentially permanent damage if not treated promptly. This condition can affect anyone, from young children to older adults, and requires a combination of medical and sometimes surgical treatment to prevent long-term complications.
Understanding How Common Osteomyelitis Is
Osteomyelitis affects a relatively small portion of the population overall, but its impact can be significant. Research suggests that fewer than 25 per 100,000 people experience this bone infection each year in the general population.[2] However, the numbers tell a different story when it comes to hospitalized patients. Studies have found that osteomyelitis may be as common as 1 out of every 675 hospital admissions in the United States, which translates to approximately 50,000 cases annually.[3][7]
This significant difference between general population rates and hospital admission rates reveals an important pattern. People who are admitted to hospitals often have health conditions or injuries that make them much more vulnerable to infections reaching their bones. The infection can occur in any bone of the body, but the location tends to vary by age. Children with osteomyelitis most commonly develop it in the long bones of their arms or legs, while adults typically experience it in the vertebrae (the bones that make up the spine) or in the hip bones.[2]
What Causes Bone Infections
Normally, healthy bone tissue has natural defenses that resist infection. However, certain circumstances can make bones vulnerable to bacterial or fungal invasion. The primary cause of osteomyelitis is infection that spreads to the bones, and this can happen through several different pathways.[1]
The most common way bones become infected is when bacteria from the skin surface, such as from a wound or surgical site, enter the bloodstream and travel to the bone marrow (the spongy tissue inside some bones where new blood cells are made). This process is called hematogenous osteomyelitis, meaning the infection spreads through the blood.[2][5] This type is particularly common in children, older adults, and people with weakened immune systems.
Another way bones can become infected is through direct contact. When someone experiences a bone fracture that breaks through the skin, undergoes surgery, or suffers a deep puncture wound, bacteria can be introduced directly into the bone tissue. This is known as nonhematogenous osteomyelitis.[5] The infection can also spread from nearby infected soft tissues or joints to adjacent bone structures.
The bacteria most commonly responsible for osteomyelitis is Staphylococcus aureus, a type of bacteria often found on the skin and in the nose. This organism has a remarkable ability to attach itself to bone tissue by producing special proteins called adhesins that bind to components of the bone matrix, including collagen and fibronectin.[3] Other bacteria that can cause bone infections include Pseudomonas aeruginosa, particularly in people who inject drugs, and various other organisms depending on the patient’s specific circumstances.[5]
Who Is at Higher Risk
While anyone can develop osteomyelitis, certain groups of people face significantly higher risk. Understanding these risk factors is important because it can help with early detection and prevention.
Age plays a significant role in susceptibility to bone infections. People who are younger than 20 or older than 50 have elevated risk compared to other age groups.[2] The very young and the elderly often have immune systems that are either still developing or declining, making it harder for their bodies to fight off infections that reach the bone.
People with diabetes face particularly high risk for developing osteomyelitis, especially in the bones of their feet. This happens because diabetes can cause nerve damage (called diabetic neuropathy) that reduces sensation in the feet, meaning small cuts or ulcers may go unnoticed until they become severely infected and spread to the bone.[1][4] Diabetes also impairs blood circulation and weakens the immune system’s ability to fight infections.
Recent injuries or medical procedures significantly increase risk. People who have had surgery, especially joint replacement surgery where artificial implants are placed in the body, are at higher risk because bacteria can attach to these foreign materials.[2] Those with open wounds from trauma, bone fractures, or puncture injuries also have pathways for bacteria to enter the bone.
Individuals with weakened immune systems are especially vulnerable. This includes people with conditions such as HIV, those undergoing chemotherapy, patients with kidney failure who require hemodialysis (a treatment that filters waste from the blood when kidneys fail), and those taking immunosuppressant medications (drugs that reduce immune system activity).[2][4] People with sickle cell anemia also have elevated risk for bone infections.
Those who inject drugs intravenously face increased risk because contaminated needles can introduce bacteria directly into the bloodstream, which can then travel to bones.[7] Smokers are also at higher risk because smoking impairs blood flow and slows the healing process, making it easier for infections to take hold and harder for the body to eliminate them.
Recognizing the Symptoms
The symptoms of osteomyelitis can vary considerably depending on the type of infection, which bones are affected, and how long the infection has been present. In some cases, particularly with chronic infections, there may be no obvious symptoms at all.[1]
The most common symptom is pain in the affected bone. This pain can range from mild to severe and typically worsens over time. The area around the infected bone often becomes swollen, red, and warm to the touch, reflecting the body’s inflammatory response to the infection.[1][4] These local signs of infection may be accompanied by a general feeling of being unwell.
Fever is a frequent symptom, particularly in acute osteomyelitis where the infection has developed rapidly. The fever may be quite high, and patients often experience chills and sweating as their body attempts to fight the infection.[2][4] Some people also experience nausea and vomiting, especially when the infection is severe or when it affects certain areas such as the spine.
When the infection affects the bones of the arms or legs, people may develop limited movement or stiffness in nearby joints. Children with osteomyelitis may develop a noticeable limp or may refuse to use an affected arm or leg, appearing irritable without necessarily running a high fever.[4][14] This behavior change can be an important early warning sign in young children who cannot clearly communicate their symptoms.
If the infection is near a wound or surgical site, there may be visible drainage of pus or other fluid from the area. When osteomyelitis affects the vertebrae in the spine, it typically causes low back pain or stiffness in the back.[2] In chronic cases that have persisted for months or years, some patients may develop visible fistulous tracts—abnormal passages that form from the infected bone through the tissue to the skin surface.[5]
Prevention Strategies
While not all cases of osteomyelitis can be prevented, there are several important steps people can take to reduce their risk of developing this serious bone infection.
Proper wound care is essential. Any cut, scrape, or injury that breaks the skin should be cleaned thoroughly and kept clean while it heals. People should watch for signs of infection such as increasing redness, warmth, swelling, or discharge, and seek medical attention if these develop. For those with diabetes, daily foot inspections are crucial to identify small wounds or ulcers before they can progress to more serious infections.[14]
Maintaining good control of chronic health conditions, particularly diabetes, significantly reduces risk. When blood sugar levels are well-managed, the immune system functions more effectively and wounds heal more readily. People with diabetes should work closely with their healthcare providers to keep their condition under control and should pay special attention to foot care.
Smoking cessation is important for reducing risk. Smoking impairs blood flow throughout the body, including to bones, and slows the healing process. This makes it easier for infections to develop and harder for the body to fight them off. Quitting smoking improves overall health and helps the body maintain its natural defenses against infection.[17]
For people undergoing surgery, following all pre-operative and post-operative instructions carefully helps prevent infection. This includes taking any prescribed antibiotics exactly as directed and keeping surgical sites clean and protected according to medical advice. People with artificial joints or other implanted medical devices should be particularly vigilant about preventing infections, as bacteria can easily colonize these foreign materials.
Maintaining a healthy immune system through proper nutrition, adequate sleep, regular exercise, and stress management helps the body resist infections more effectively. For people who are immunocompromised due to medical conditions or treatments, working closely with healthcare providers to minimize infection risk is especially important.
How the Disease Affects the Body
Understanding what happens inside the body when osteomyelitis develops helps explain why this condition is so serious and why it requires aggressive treatment.
When bacteria or fungi reach bone tissue, they trigger an immune response. White blood cells rush to the area to fight the infection, causing inflammation. This inflammatory process leads to the swelling, warmth, and redness visible on the outside of the body. Inside the bone, however, the infection can cause more serious problems.[3]
As the infection progresses, it can interfere with blood flow to the bone. Blood vessels may become blocked or damaged, depriving bone tissue of the oxygen and nutrients it needs to survive. Without adequate blood supply, sections of bone can die, a process called necrosis. Dead bone tissue is called a sequestrum, and it creates a serious problem because antibiotics and immune cells cannot reach dead tissue effectively through the bloodstream.[1][6]
The body may respond to a sequestrum by forming new bone around it, creating a shell called an involucrum. While this is an attempt to wall off the infection, it can actually trap the infection inside, making it extremely difficult to eliminate without surgical intervention. Pockets of pus called abscesses may form within the bone or in the surrounding soft tissues.[4]
In acute osteomyelitis, these changes develop rapidly over days to weeks. The infection causes intense inflammation but hasn’t yet caused significant bone death. If treated quickly and aggressively during this acute phase, the infection can often be completely eliminated. However, if treatment is delayed or inadequate, the infection can become chronic.[5]
Chronic osteomyelitis develops over months to years of persistent infection. It is characterized by the presence of dead bone tissue and may involve the formation of fistulous tracts—abnormal channels that tunnel from the infected bone through the tissues to the skin surface, allowing drainage.[5] Chronic infections can have periods where they seem to be inactive or improved, followed by sudden flare-ups where symptoms return. This pattern of quiescence and recurrence can continue for years, making chronic osteomyelitis particularly challenging to manage.
