History of mono-arthritis of the right knee. Actually recurrent episodes of pain at the right knee. On physical examination there was swelling and local warmth.
The patient with a history of mono-arthritis of the right knee presented with recurrent episodes of pain at the right knee. On physical examination there was swelling and local warmth. Conventional radiographs, CT scan and MRI were performed. Based on medical history and imaging findings – especially on MRI – the diagnosis of Brodie’s abscess with cortical fistulization and paraosseous extension was made. The abscess was drained surgically. The abscess cavity was filled with Gentamycin pearls and antibiotics were given intravenously during 6 weeks. Culture demonstrated presence of Staphylococcus aureus.
Acute hematogenous osteomyelitis is most commonly seen in children and characterized by accumulation of the pathogenic organisms in the terminal arterioles and capillars of the bone metaphysis. In children a boy to girl ratio of 3/1 is seen. As edema and granulation occur, the intraosseous pressure may increase and result in bone necrosis due to compression of the vascular structures. These may lead to formation of a Brodie’s abscess. In adults other pathogenic mechanisms of osteomyelitis are more common and include traumatic inoculation and spread from a nearby infected focus. Brodie’s abscess as located form of chronic osteomyelitis is very common in children, due to high vascularity of the metaphysis and growth plates. Metaphyseal locations are most common before closure of the growth plates. After closure, a metaepiphyseal abscess is most frequent. When not hematogeneous in etiology, they occur most frequently in young adults at the long bones of the lower extremities. Pathologically, the wall of the abscess contains large amounts of granulation tissue, accounting for pronounced rim enhancement on contrast-enhanced MRI or CT scans. The central portions are mainly constituted by necrotic fluid and pathologic organisms. Staphylococcus aureus is cultured in half of the cases. The abscess is commonly surrounded by inflammatory changes and edema of adjacent bone marrow. Transcortical fistulization may lead to soft tissue spread. Until recently, early detection of bone abscedation was only possible by bone scintigraphy. This technique however is non-specific, as neoplastic changes or avascular necrosis revealed similar changes. MRI is considered more specific and furthermore allows better anatomical and topographical evaluation of disease extent. Only advanced stages of bone abscess are seen on conventional radiographs as areas of bone sclerosis with central radiolucency and eventually periosteal reaction and bone sequestration within the abscess.
Brodie’s abscess
Based on the provided X-ray, CT, and MRI images, a relatively clear lytic lesion is observed in the bone near the articular surface of the distal femur (or tibia) of the right knee. There are varying degrees of sclerosis around the lesion. On CT, the center of the lesion shows a low-density area with a sclerotic, enhanced margin. On MRI, the lesion center appears with high T2 signal and low or intermediate T1 signal, demonstrating obvious ring enhancement after contrast administration, along with varying degrees of bone marrow edema and inflammatory changes in the local soft tissue. These characteristics suggest a focal abscess within the bone accompanied by surrounding inflammatory reactions.
Combining the patient’s age, clinical symptoms (periodic knee pain, recurrent episodes, localized feverish sensation) and imaging findings, the possible diagnoses and differential diagnoses include:
Among these differentials, recurrent pain, inflammatory signs, and typical ring enhancement on imaging are most consistent with subacute/chronic osteomyelitis, especially Brodie’s abscess.
Considering the patient is a 42-year-old adult who has experienced multiple recurrences of localized right knee pain, swelling, and increased temperature, along with imaging findings indicative of a localized abscess within the bone, the most likely final diagnosis is:
Right Knee Brodie’s Abscess (Subacute or Chronic Osteomyelitis)
If necessary to confirm the etiological agent, aspiration or biopsy with pathogen culture could be performed to guide targeted anti-infective therapy.
1. Treatment Strategy:
• Antibiotic Therapy: Based on microbiological findings or empirical treatment, choose antibiotics highly effective against Staphylococcus aureus. Treatment duration is usually longer than in acute osteomyelitis, often extending from several weeks to months.
• Surgical Management: If the abscess cavity is large or conservative treatment is not effective, consider curettage of the lesion, debridement, and bone grafting or other filling procedures. Drainage may be needed to prevent re-formation of the abscess.
• Supportive Care: Pain management and measures to reduce swelling, such as appropriate immobilization or bracing, to avoid exacerbating the condition.
2. Rehabilitation/Exercise Prescription Suggestions:
• Early Stage (Acute/Subacute Phase):
This report is for medical reference only and does not replace an in-person consultation or the professional opinion of a qualified physician. If you have any questions or changes in your condition, please consult a specialist and undergo appropriate examinations and treatment.
Brodie’s abscess
