Meniscitis

Meniscitis is inflammation of the meniscus, the crescent-shaped cartilage within the knee joint. It is uncommon; most meniscal problems arise from trauma or degenerative changes, while infectious involvement of the meniscus is rare and usually occurs in the setting of septic arthritis or after direct inoculation from injury or surgery.

Causes and pathophysiology: Infectious meniscitis typically results from spread of bacteria to the meniscus during septic arthritis, from hematogenous seeding, or by contamination during procedures. Common organisms include Staphylococcus aureus and streptococci; gram-negative bacteria may be involved, particularly in certain patient groups. Immunocompromised status, diabetes, and recent knee surgery increase risk.

Clinical features: Patients usually present with knee pain and swelling, warmth, and reduced range of motion. Fever may be present in infectious cases. Joint effusion is common, and tenderness may be felt along the joint line. The presentation can resemble isolated meniscal injury or general septic arthritis.

Diagnosis: Evaluation includes inflammatory markers such as CRP and ESR and sometimes leukocytosis. Imaging, especially magnetic resonance imaging, helps assess the meniscus and surrounding structures. Definitive diagnosis relies on analysis of synovial fluid with microscopy and culture; Gram stain and culture can identify the organism. In some cases, arthroscopic biopsy or washout is performed.

Treatment and prognosis: Infectious meniscitis requires prompt joint drainage (aspiration or arthroscopic washout) and empiric intravenous antibiotics, later tailored to culture results. Duration is typically several weeks. Noninfectious inflammatory processes are managed with standard anti-inflammatory care and treatment of the underlying condition. Early diagnosis and treatment improve outcomes and reduce the risk of cartilage damage and chronic knee arthritis.