Septic arthritis, which is sometimes called septic arthritis is a suppurative
inflammation within a joint space, most commonly due to haematogenous spread, but
sometimes due to direct spread from a penetrating wound or a
neighboring infection, for
example chronic osteomyelitis.
Most commonly affected are children, premature neonates, the elderly and the immune
Generally, this disease is monoarticular, and occurs often in the knee and the hip, but
may involve any joint. In infants there can be multiple joint involvement. Note that
septic arthritis of the hip may present as pain in the knee and vice-versa.
Information about Septic Arthritis
Septic arthritis can occur in any age group, including newborns and children. In
adults, it usually affects the wrists or one of the patient's weight-bearing joints--most
often the knee--although about 20% of adult patients have symptoms in more than one joint.
Multiple joint infection is common in children and typically involves the shoulders,
knees, and hips.
Some groups of patients are at greater risk for developing Septic arthritis. These
high-risk groups include:
- Patients with chronic rheumatoid arthritis.
- Patients with certain systemic infections, including gonorrhea and HIV infection. Women
and male homosexuals are at greater risk for gonorrheal arthritis than are male
- Patients with certain types of cancer.
- IV drug abusers and alcoholics.
- Patients with artificial (prosthetic) joints.
- Patients with diabetes, sickle cell anemia, or systemic lupus erythematosus (SLE).
- Patients with recent joint injuries or surgery, or patients receiving medications
injected directly into a joint.
Symptoms of Septic Arthritis
Symptoms of septic arthritis occur suddenly and are characterized by severe pain,
swelling in the affected joint along with acute pain. Chills and fever are also common
symptoms. Septic arthritis in the hip may be experienced as pain in the groin area that
becomes much worse if the patient tries to walk. In the majority of cases, there is some
leakage of tissue fluid into the affected joint. The joint is sore to the touch, and may
or may not be warm to the touch, depending on how deep the infection lies within the
joint. Children sometimes develop nausea and vomiting.
Causes of Septic Arthritis
In general, Septic arthritis is caused by the spread of a bacterial, viral, or fungal
infection through the bloodstream to the joint. The disease agents may enter the joint
directly from the outside as a result of an injury or a surgical procedure, or they may be
carried to the joint by the blood from infections elsewhere in the body. The specific
organisms vary somewhat according to age group. Newborns are most likely to acquire
gonococcal infections of the joints from a mother with gonorrhea. Children may also
acquire Septic arthritis from a hospital environment, often as a result of catheter
placement. The organisms involved are usually either Haemophilus influenzae (in
children under two years of age) or Staphylococcus aureus. In older children or
adults, the infectious organisms include Streptococcus pyogenes and Streptococcus
viridans as well as Staphylococcus aureus. Staphylococcus epidermidis is
usually involved in joint infections related to surgery. Sexually active teenagers and
adults frequently develop Septic arthritis from Neisseria gonorrhoeae infections.
Older adults are often vulnerable to joint infections caused by gram-negative bacilli,
including Salmonella and Pseudomonas.
Septic arthritis often has a sudden onset, but symptoms sometimes develop over a period
of three to 14 days. The symptoms include swelling in the infected joint and pain when the
joint is moved. Septic arthritis in the hip may be experienced as pain in the groin area
that becomes much worse if the patient tries to walk. In 90% of cases, there is some
leakage of tissue fluid into the affected joint. The joint is sore to the touch; it may or
may not be warm to the touch, depending on how deep the infection lies within the joint.
In most cases the patient will have fever and chills, although the fever may be only
low-grade. Children sometimes develop nausea and vomiting.
Septic arthritis is considered a medical emergency because of the damage it causes to
bone as well as cartilage, and its potential for creating septic shock, which is a
potentially fatal condition. Staphylococcus aureus is capable of destroying
cartilage in one or two days. Destruction of cartilage and bone in turn leads to
dislocations of the joints and bones. If the infection is caused by bacteria, it can
spread to the blood and surrounding tissues, causing abscesses or even blood poisoning.
The most common complication of Septic arthritis is osteoarthritis.
Diagnosis of Septic Arthritis
Your doctor will diagnose septic arthritis based upon your symptoms, your medical
history, a complete physical exam, and synovial fluid and blood tests. After numbing the
area, he or she will withdraw a sample of synovial fluid from the affected joint. This
fluid will be tested for white blood cells, which are usually high, and for bacteria and
other organisms. Some of the joint fluid will be placed in a special container in which
many types of bacteria can grow and be identified.
The doctor may perform an arthrocentesis, which is a procedure that
involves withdrawing a sample of synovial fluid from the joint with a needle and syringe
for testing. The doctor may also perform a culture of blood and urine to rule out other
causes such as gout, acute rheumatic fever, rheumatoid arthritis, Lyme disease and other
disorders that can cause a combination of joint pain and fever. In some cases, the doctor
may consult a specialist in orthopedics or rheumatology to avoid misdiagnosis.
Because septic arthritis can quickly destroy a joint unless treated, your doctor may also
order x-rays to assess any joint damage.
Laboratory testing is necessary to confirm the diagnosis of Septic arthritis. The
doctor will perform an arthrocentesis, which is a procedure that involves withdrawing a
sample of synovial fluid (SF) from the joint with a needle and syringe. SF is a
lubricating fluid secreted by tissues surrounding the joints. Patients should be warned
that arthrocentesis is a painful procedure. The fluid sample is sent for culture in the
sealed syringe. SF from infected joints is usually streaked with pus or looks cloudy and
watery. Cell counts usually indicate a high level of white cells; a level higher than
100,000 cells/mm3 or a neutrophil proportion greater than 90% suggests septic arthritis. A
Gram's stain of the culture obtained from the SF is usually positive for the specific
Doctors sometimes order a biopsy of the synovial tissue near the joint if the fluid
sample is negative. Cultures of other body fluids, such as urine, blood, or cervical
mucus, may be taken in addition to the SF culture.
Diagnostic imaging is not helpful in the early stages of Septic arthritis. Destruction
of bone or cartilage does not appear on x rays until 10-14 days after the onset of
symptoms. Imaging studies are sometimes useful if the infection is in a deep-seated joint.
Treatment of Septic Arthritis
Septic arthritis must be diagnosed quickly and treated with antibiotics. Your doctor
may first give these antibiotics intravenously (through a vein) to make sure the infected
joint receives medication to kill the bacteria as quickly as possible. Then, the remaining
course of antibiotics is taken orally.
The doctor may also need to drain the fluid from the infected joints if it rapidly
reaccumulates and causes symptoms. Immediate surgical drainage is reserved for septic
arthritis of the hip, because that site is inaccessible for repeated fluid removal. For
most other joints, surgical drainage is used only if medical therapy fails over two to
four days to alleviate symptoms. Hot compresses and splinting the joint to provide
it with rest and support can help relieve pain. After a period of rest, your doctor will
recommend gentle exercise to prevent stiffness. If septic arthritis occurs in an
artificial joint, antibiotic treatment may need to be followed by surgery to replace the
joint. Most patients with no other serious underlying disease recover fully from septic
arthritis with antibiotic therapy.
Recovery from septic arthritis is usually good with most patients undergoing treatment,
although many patients will develop osteoarthritis or deformed joints. Children with
infected hip joints sometimes suffer damage to the growth plate. Patients with severe
damage to bone or cartilage may need reconstructive surgery, but it cannot be performed
until the infection is completely gone.
Medications for Septic arthritis
Because of the possibility of serious damage to the joint or other complications if
treatment is delayed, the patient will be started on intravenous antibiotics before the
specific organism is identified. After the disease organism has been identified, the
doctor may give the patient a drug that targets the specific bacterium or virus.
Nonsteroidal anti-inflammatory drugs are usually given for viral infections.
Intravenous antibiotics are given for about two weeks, or until the inflammation has
disappeared. The patient may then be given a two- to four-week course of oral antibiotics.
Surgery for Septic arthritis
In some cases, surgery is necessary to drain fluid from the infected joint. Patients
who need surgical drainage include those who have not responded to antibiotic treatment,
those with infections of the hip or other joints that are difficult to reach with
arthrocentesis, and those with joint infections related to gunshot or other penetrating
Patients with severe damage to bone or cartilage may need reconstructive surgery, but
it cannot be performed until the infection is completely gone.
Monitoring and supportive treatment for Septic arthritis
Septic arthritis requires careful monitoring while the patient is in the hospital. The
doctor will drain the joint on a daily basis and remove a small sample of fluid for
culture to check the patient's response to the antibiotic.
Septic arthritis often causes intense pain. Patients are given medications to relieve
pain, together with hot compresses or ice packs on the affected joint. In some cases the
patient's arm or leg is put in a splint to protect the sore joint from accidental
movement. Recovery can be speeded up, however, if the patient practices range-of-motion
exercises to the extent that the pain allows.
Prognosis of Septic arthritis
The prognosis depends on prompt treatment with antibiotics and drainage of the infected
joint. About 70% of patients will recover without permanent joint damage. However, many
patients will develop osteoarthritis or deformed joints. Children with infected hip joints
sometimes suffer damage to the growth plate. If treatment is delayed, Septic arthritis has
a mortality rate between 5% and 30% due to septic shock and respiratory failure.
Prevention of Septic arthritis
Some cases of Septic arthritis are preventable by lifestyle choices. These include
avoidance of self-injected drugs; sexual abstinence or monogamous relationships; and
prompt testing and treatment for suspected cases of gonorrhea. Patients receiving
corticosteroid injections into the joints for osteoarthritis may want to weigh this
treatment method against the increased risk of Septic arthritis.