Differential Diagnosis for Suspected Synovitis of First MTP and IP Joints
Single Most Likely Diagnosis
- Osteoarthritis (OA): The first metatarsophalangeal (MTP) joint is a common site for OA, especially in older adults, due to its high stress and load-bearing function. OA can lead to synovitis and is often associated with pain, stiffness, and limited mobility.
Other Likely Diagnoses
- Gout: Gouty arthritis frequently affects the first MTP joint, causing acute synovitis, pain, and swelling. The presence of urate crystals in the joint fluid can confirm the diagnosis.
- Rheumatoid Arthritis (RA): Although less common in the first MTP joint compared to other joints, RA can cause synovitis and should be considered, especially if there are symptoms of systemic arthritis or involvement of other joints.
- Psoriatic Arthritis: This condition can cause synovitis in the first MTP and IP joints, often accompanied by skin and nail changes typical of psoriasis.
Do Not Miss Diagnoses
- Septic Arthritis: Although less likely, septic arthritis is a medical emergency that requires prompt diagnosis and treatment to prevent joint destruction and systemic complications. Fever, significant pain, and swelling are red flags for septic arthritis.
- Lyme Arthritis: In endemic areas, Lyme disease can cause arthritis, including synovitis of the first MTP joint. It is essential to consider this diagnosis to initiate appropriate antibiotic treatment.
Rare Diagnoses
- Reactive Arthritis: Previously known as Reiter's syndrome, this form of arthritis can occur after certain bacterial infections and may affect the first MTP and IP joints, although it is less common.
- Sarcoidosis: This systemic disease can cause arthritis, including synovitis, although it is a rare cause of joint symptoms in the first MTP and IP joints.
- Hemochromatosis: In advanced cases, hemochromatosis can lead to arthropathy, including synovitis, due to iron deposition in the joints, but this is a rare condition.