Differential Diagnosis for Right Knee Pain and Swelling
Single Most Likely Diagnosis
- Gout: The patient's symptoms of warmth, swelling, erythema, and a history of gout flare-ups make gout the most likely diagnosis. The use of crutches suggests significant pain and disability, which is consistent with a gout flare-up.
Other Likely Diagnoses
- Pseudogout (Calcium Pyrophosphate Deposition Disease): Similar to gout, pseudogout can cause sudden, severe joint pain and swelling, often accompanied by warmth and erythema.
- Septic Arthritis: Although less likely, septic arthritis is a possible diagnosis, especially if the patient has a history of joint injections, recent trauma, or immunocompromised status.
- Osteoarthritis: While osteoarthritis is a common cause of knee pain, it typically presents with more chronic symptoms and may not fully explain the acute onset of warmth, swelling, and erythema.
Do Not Miss Diagnoses
- Septic Arthritis: As mentioned earlier, septic arthritis is a medical emergency that requires prompt diagnosis and treatment to prevent joint destruction and potential systemic complications.
- Deep Vein Thrombosis (DVT): Although less common, DVT can cause warmth, swelling, and erythema in the affected limb, and it is essential to consider this diagnosis, especially if the patient has risk factors such as recent surgery, immobilization, or cancer.
- Cellulitis: A bacterial skin infection can cause similar symptoms, and it is crucial to distinguish cellulitis from other diagnoses, as it requires antibiotic treatment.
Rare Diagnoses
- Rheumatoid Arthritis: Although rheumatoid arthritis can cause knee pain and swelling, it typically presents with more systemic symptoms, such as fever, fatigue, and symmetric joint involvement.
- Hemarthrosis: Bleeding into the joint space can cause sudden onset of pain, swelling, and warmth, but it is a rare condition, often associated with trauma, bleeding disorders, or anticoagulant use.
- Lyme Arthritis: A rare cause of knee pain and swelling, Lyme arthritis typically presents with a distinctive "bull's-eye" rash and a history of tick exposure.