Infections (Septic Joint, Septic Arthritis, and Osteomyelitis)


Osteomyelitis can take on both acute and chronic forms. Chronic osteomyelitis involves the development of necrotic bone and can involve complications such as sinus tract formation. Osteomyelitis can develop from the hematogenous spread of bacteria, which is more common in children and patients older than 50 years of age. Osteomyelitis can also develop from contiguous spread through soft-tissue infections and from local inoculation after surgery or trauma. Symptoms can be vague and nonspecific, and adults are more likely to have few constitutional symptoms. A high index of suspicion must be maintained, as early recognition and treatment can prevent long-term complications. Magnetic resonance imaging and triple-phase bone scan are sensitive and can show evidence of osteomyelitis within a few days; however, there are pitfalls associated with all imaging modalities that must be considered. Early surgical consultation and empiric antibiotic therapy are vital.

Septic arthritis can involve a variety of pathogens, including bacteria, viruses, spirochetes, and fungi. Bacterial pathogens are most clinically significant due to their rapidly destructive nature. Acute onset of joint pain is common, and systemic symptoms including fever may be present. Imaging studies can be useful to detect joint effusions and to rule out surrounding osteomyelitis. Arthrocentesis with synovial fluid analysis and cultures is key to determining the causative organism and in guiding antimicrobial therapy. Surgical drainage may be needed if medical therapy fails. Early recognition and treatment are crucial to prevent chronic pain and deficits in range of motion.


Osteomyelitis, septic arthritis, infectious arthritis, antibiotics


ICD-10-CM Codes

M86.10 Acute Osteomyelitis, Unspecified Site
M86.60 Chronic Osteomyelitis, Unspecified Site
M00.80 Septic Arthritis


Key Concepts

  • Acute osteomyelitis is an acute infection of bone without the development of necrotic bone (sequestra). The duration is variable, but the condition usually evolves over several days to weeks.

  • Chronic osteomyelitis is a long-term infection of bone with the presence of dead bone (the sequestrum). Common features include reactive bony encasement of the sequestrum (involucrum), local bone loss, and the possibility of sinus tract development if there is extension of the infection through cortical bone.

  • The pathogenesis can include hematogenous spread of bacteria, contiguous spread from a soft-tissue infection, and local inoculation after surgery or trauma.

  • Hematogenous spread has a biphasic distribution, occurring in children due to their unique bone anatomy and in patients older than the age of 50 who have increased risk factors for bacteremia.

  • The long bones are most often involved in children. In adults, the vertebrae and sternoclavicular and sacroiliac bones are most commonly involved.

  • This is a difficult disease to diagnose; testing must be tailored to the clinical scenario and may require bone biopsy for definitive diagnosis.

  • When present, positive blood cultures with typical radiographic changes obviate the need for a bone biopsy.


  • Signs and symptoms can vary with duration of disease.

    • Acute osteomyelitis

      • Typically has an insidious onset over several days to a week with bone pain, tenderness, warmth, and swelling

      • Fevers can be present, and pain occurs with and without movement. Complaints can be vague and nonspecific, with few constitutional symptoms.

    • Chronic osteomyelitis

      • May be subtle with few symptoms. There may be a history of chronically developing skin changes or ulcerations, bone pain, or concomitant medical issues including diabetes and peripheral vascular disease.

      • Easily recognized if there is a draining sinus along with recurrent pain, erythema, and swelling in someone with a known history of osteomyelitis

Physical Examination

  • Acute osteomyelitis

    • Children

      • If hematogenous in origin, likely to have fever and local signs of inflammation

      • A limp or refusal to walk may be observed if the spine, pelvis, or lower extremity is involved. Pseudoparalysis may occur when the upper extremity is involved.

    • Adults

      • Usually present with vague, nonspecific pain and few constitutional symptoms

      • Limitation of joint motion, swelling, erythema, fever, and a symptomatic effusion

  • Chronic osteomyelitis

    • External physical findings may be minimal; however, soft-tissue inflammation and tenderness may develop.

    • Persistent drainage through a sinus tract or fistula, low-grade fever, chronic pain, local bone loss, and mild systemic symptoms may be present.


  • Plain radiographs

    • Acute osteomyelitis

      • Two to three weeks are required for bone changes to be evident.

      • The triad of soft-tissue swelling, bone destruction, and periosteal reaction is specific.

    • Chronic osteomyelitis

      • Bone sclerosis, periosteal bone formation, and sequestra are the primary findings.

  • Ultrasonography

    • Findings may include a fluid collection adjacent to the bone and periosteal elevation by more than 2 mm with thickening.

    • Larger studies are needed to evaluate the sensitivity and specificity of this modality.

  • Computed tomography

    • Detects cortical destruction, periosteal reaction, intraosseous gas, soft-tissue extension

  • Magnetic resonance imaging

    • Provides anatomic detail when planning surgical débridement and identifying abscesses

    • High sensitivity and negative predictive value; shows bone marrow edema within 3 to 5 days of infection

    • Especially advantageous when evaluating vertebral or foot osteomyelitis

  • Three-phase bone scan

    • Historically considered the test of choice when evaluating acute osteomyelitis if plain radiographs are normal. The scan generally turns positive in 2 to 3 days.

    • More useful when metal hardware limits the quality of MRI images

    • Osteomyelitis results in increased uptake in all three phases, making it useful when differentiating from cellulitis but limited in differentiating from gouty arthritis and conditions with high bony turnover.

Additional Tests

  • Laboratory studies

    • Complete blood count—leukocytosis common in acute, but not chronic, osteomyelitis

    • Erythrocyte sedimentation rate/C-reactive protein—may be markedly increased

    • Monitoring can be useful to detect relapses.

  • Cultures

    • Blood (positive in 50% of cases-of-acute osteomyelitis)

  • Bone biopsy

    • The gold standard is an open bone biopsy with histopathologic examination and cultures.

Differential Diagnosis

  • Cellulitis

  • Gout

  • Acute leukemia

  • Bone malignancy

  • Septic arthritis

  • Rheumatic fever

  • Bone infarct (i.e., sickle cell disease)


Sep 17, 2019 | Posted by in ORTHOPEDIC | Comments Off on Infections (Septic Joint, Septic Arthritis, and Osteomyelitis)
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