Pyogenic arthritis is a joint infection caused by pus-forming bacteria, most frequently via the bloodstream. Risk factors include age older than 80 years, immunosuppression, and underlying arthropathies. Involvement is usually monoarticular, and Staphylococcus aureus is the most common pathogen. Radiography is the first-line imaging modality for suspected pyogenic arthritis, detecting preexisting conditions and ruling out certain differential diagnoses. Ultrasound (US) imaging shows joint effusion and synovitis with high sensitivity and guides synovial fluid aspiration, compensating for its low specificity in diagnosing pyogenic arthritis. Magnetic resonance imaging (MRI) is the most sensitive and specific imaging modality for early diagnosis. Some imaging signs that help suggest joint infection include the presence of gas, adjacent osteomyelitis or soft tissue abscess, and restricted diffusion of synovial fluid. Diagnosis confirmation is made by bacteria identification in synovial fluid, which may be obtained by imaging guidance. Treatment is medico-surgical, with early diagnosis and management being key for favorable outcomes. Pyogenic bursitis most commonly affects the olecranon and prepatellar bursae. Bacterial inoculation is frequently by microtrauma or direct puncture, with Staphylococcus aureus being the most common pathogen. Radiography helps detect foreign bodies, while US imaging and MRI exclude adjacent joint lesions and show bursal distension with vascularized synovial thickening and adjacent soft tissues edema. Diagnosis is established by fluid aspiration from the affected bursa. Treatment is based on antibiotic therapy. Prognosis is good in most patients. Pyogenic tenosynovitis is infection of a tendon and its synovial sheath, usually by direct inoculation, with predilection for the hand flexor tendons. Staphylococcus aureus is the most common pathogen. Diagnosis is based on physical examination and clinical suspicion. Imaging confirms tenosynovitis and assesses the infection extent. Surgical management is usually required.