What causes synovitis in the knee?

Mechanical and wear-related causes

• Osteoarthritis: the most common cause in adults over about 50; flares follow busy days, stairs or long standing
• Meniscus tears and cartilage flaps: the torn edge irritates the lining
• Loose bodies: fragments of bone or cartilage floating in the joint
• Ligament injury or instability: repeated giving way inflames the joint
• Overload: a sudden rise in training, walking or weight bearing

Crystal and inflammatory causes

• Gout: urate crystals, often a sudden, very painful red knee; linked to diet, alcohol, dehydration, kidney function and some medicines
• Pseudogout: calcium crystals, more common in older adults, sometimes after surgery or illness
• Rheumatoid arthritis and other autoimmune conditions: often several joints, morning stiffness lasting more than half an hour
• Psoriatic arthritis, reactive arthritis after a bowel or urinary infection, and inflammatory bowel disease

Infection and rarer causes

• Septic arthritis: bacteria in the joint; a hot, very painful knee, often with fever; an emergency
• Tenosynovial giant cell tumour, previously called PVNS: a benign overgrowth of the lining causing recurrent swelling
• Bleeding into the joint in people with bleeding disorders or on blood thinners
• Lyme disease and tuberculosis are rare causes, considered in particular circumstances

Finding your cause in Doha

Your age, how fast the swelling came, whether other joints hurt, and your medical history narrow the list quickly. At Aman Hospital Dr. Gelber examines the knee, and often uses fluid testing, blood tests and MRI to confirm the cause. In Qatar, summer dehydration can help trigger gout flares, so it is worth mentioning recent heat exposure or fasting.