Early diagnosis and treatment of acute brucellosis knee arthritis complicated by acute osteomyelitis: two cases report

Abstract

Background: Brucellosis is an endemic systemic infectious disease, the most common complication is bone and joint involvement. Sacroiliac joint and spinal joint are the most frequently involved sites in adults, but knee joint infection is rare, and acute infectious knee arthritis complicated by acute osteomyelitis is even extremely uncommon in adults. Here, we report two cases of acute septic knee arthritis complicated by acute osteomyelitis caused by Brucella melitensis (B. melitensis).

Case presentation: Both patients had a history of traveling in animal husbandry areas within three months. On clinical examination, their right knee joint was tender, swollen, had limited movement and an effusion was present. Imaging examination showed effusion and synovial thickening of the right knee joint, as well as subchondral bone edema of the distal femur and proximal tibia. Laboratory examination showed that the serum agglutination test (SAT) in both patients were positive (1: 640 and 1: 320) without leukocytosis, although the proportion of lymphocytes, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) significantly increased. Both patients underwent knee joint aspiration. Real-time polymerase chain reaction (Real-time PCR) analysis of synovial fluid showed that there was B. melitensis, and blood bacterial culture was negative. We determined that two patients had acute brucellosis knee arthritis complicated by acute osteomyelitis. Antibiotic treatment was given during hospitalization consisting of doxycycline (0.1 g po bid) and rifampicin (0.6 g po qd) for six weeks, and the changes of inflammatory indexes were closely monitored. At discharge, the symptoms had completely resolved, imaging abnormalities disappeared, and inflammatory indexes returned to normal. There was no recurrence of the disease at 1-year follow-up.

Conclusion: Acute brucellosis knee arthritis complicated by acute osteomyelitis is a rare but serious complication of brucellosis in adults. There is no obvious specificity of clinical manifestation and imaging examination. Early diagnosis and treatment can prevent the occurrence of knee joint deformity and even pathological fracture. Clinicians should fully consider the possibility of brucellosis where the travel or occupational history is suggestive.

Keywords: Acute osteomyelitis; Brucellosis; Septic knee arthritis; Synovitis.

Fig. 1

Patient 1: X-ray images showed multiple cystic low density areas (blue circle) of distal right femur and proximal tibia (a, b). PDWI sequence of MRI showed effusion and synovial thickening of the right knee joint, and subchondral bone marrow edema (blue circle) of the distal femur and proximal tibia (c–e). Post-treatment X-ray images showed the low density area was significantly reduced (f, g). Post-treatment PDWI sequence of magnetic resonance images indicates the high signal area of bone marrow edema had disappeared (h–j)

Fig. 2

Patient 1: The Real-time PCR of purulent joint synovial fluid of right knee showed that there was Brucella melitensis in the synovial fluid, DNA content of Brucella melitensis (Solid red line) increased in 35 cycles

Fig. 3

Patient 2: X-ray showed no obvious abnormality (a, b). PDWI sequence of MRI showed effusion, synovitis and bone marrow edema (blue arrow) deep to the surface of the right femoral trochlea and tibial plateau (c–e). Post-treatment X-ray images showed no obvious abnormality (f, g). Post-treatment PDWI sequence of magnetic resonance images indicates the edema of bone marrow disappeared and the effusion in articular cavity decreased significantly (h–j)

Fig. 4

Patient 2: The Real-time PCR of purulent synovial fluid of right knee joint showed that there was Brucella melitensis, DNA content of Brucella melitensis (Solid red line) increased in 31 cycles