Week 8 – Joints n Stuff

Pseudogout generally affects middle-aged and elderly patients. Pseudogout is a type of crystal-induced synovitis that is caused by calcium pyrophosphate crystals. These crystals are positively birefringent and are rhomboid shaped. Patients will present complaining of joint pain, swelling, and redness. Joints most commonly affected are the knee, wrist, ankle, and elbow. Pseudogout is a type of inflammatory arthritis that is diagnosed and confirmed by synovial fluid analysis. Synovial fluid for an inflammatory arthritis will have a white blood cell count between 200 and 50 000 with a predominance of neutrophils (generally greater than 50%). The appearance of the synovial fluid will be cloudy and yellow with positive birefringent, rhomboid shaped crystals. Treatment includes the use of nonsteroidal anti–inflammatory drugs and opioid analgesics. Corticosteroids are an option in patients with a history chronic kidney disease or patients the provider thinks may be of benefit. Avoid corticosteroids in uncontrolled diabetics given the risk of worsening hyperglycemia. Colchicine is not routinely used due to its side effect profile, however, it may be used in refractory cases or in cases where NSAIDs and corticosteroids cannot be used.

Gout (A) is also a type of inflammatory crystal-induced synovitis, however, it is caused by uric acid crystal deposition. Gout generally affects middle-aged and elderly patients. Uric acid crystals are needle shaped and are negatively birefringent. Patients will present complaining of arthritis, edema, and erythema. The joints most commonly affected are the great toe, tarsal joints, and knee. Synovial fluid analysis will be similar to pseudogout, as both are an inflammatory arthritis. Differentiating the two is based on the characteristic crystal formation. Thus, crystal analysis is imperative to the correct diagnosis. However, treatment remains the same as with pseudogout and so synovial fluid analysis is performed more to rule out septic arthritis. Osteoarthritis (B) is a symmetric and chronic polyarticular joint disease distinguished by the lack of constitutional symptoms. Patients may present with acute exacerbations of monoarticular pain that consists on joint pain and inflammation. Synovial fluid analysis will demonstrate a white blood cell count of less than 200 cells with fewer than 25% neutrophils. The synovial fluid will be have a clear and transparent appearance without crystals. Treatment consists of rest and analgesics. Septic arthritis (D) is a condition that can rapidly lead to irreversible joint destruction if not recognized and treated. Patients will typically present with a monoarticular arthritis and may have associated fever, chills, and malaise. Septic arthritis should be differentiated from periarticular processes such as cellulitis, bursitis, and tendinitis. A true arthritis will produce pain that is exacerbated through active and passive range of motion. Synovial fluid analysis for septic arthritis will demonstrate a significantly elevated white blood cell count typically greater than 50 000 cells with a predominance of neutrophils (greater than 50%). The synovial fluid will be cloudy and yellow in appearance. Admission for parenteral antibiotics and repeated needle aspiration, arthroscopy, or open surgical drainage is required.

Septic arthritis is a bacterial or fungal infection of a joint typically spread hematogenously unless there is direct bacterial contamination. The synovium is highly vascular and lacks a basement membrane making it susceptible to bacterial seeding. Certain conditions predispose individuals to septic arthritis including diabetes, sickle cell disease, immunocompromise, alcoholism or pre-existing joint disease like rheumatoid arthritis or gout. Fever is present in less than half of cases of septic arthritis so with clinical suspicion an arthrocentesis is indicated. The knee is the most common joint affected and patients have pain (especially on passive range of motion) and decreased range of motion often accompanied by warmth, erythema and fever. This patient may have an acute gouty flare, but the clinician must exclude an infection. On joint fluid analysis, the white blood cell count of a septic joint is typically > 50,000.

Indomethacin (B) is a non-steroidal anti-inflammatory agent commonly used in the treatment of acute gout. Gout is arthritis caused by deposition of monosodium urate monohydrate crystals in the joint space. Acute flares involve a monoarticular arthritis with a red, hot, swollen and tender joint. Acute episodes of gout result from overproduction or decreased secretion of uric acid. However, measurement of serum uric acid (C) does not correlate with the presence or absence of an acute flare. A radiograph of the knee (D) may show chronic degenerative changes associated with gout but will not help to differentiate gouty arthritis versus septic arthritis.

Septic Arthritis

• Patient will be complaining of fever, monoarticular pain with decreased ROM
• Labs will show WBC > 50,000 with > 75% PMNs
• Diagnosis is made by arthrocentesis
• Most commonly caused by:
  • Age < 35: N. gonorrhea, S. aureus overall
• Treatment is IV ABX, surgical washout

Allopurinol therapy should never be initiated until an acute attack has subsided. Allopurinol is a xanthine oxidase inhibitor that decreases uric acid production but also produces a more soluble metabolite. Allopurinol is therefore effective regardless of the cause of the hyperuricemia. Gout is caused by deposition of uric acid crystals in the synovium, bursae, tendon sheaths, skin, heart valves, and kidneys, which can lead to arthritis, tophi, renal stones, and gouty nephropathy. Typically, patients present with acute, exquisitely tender, monoarticular arthritis. The joint is usually warm and erythematous. The first metatarsophalangeal joint (MTP) joint is most commonly affected. Detecting negatively birefringent, needle-like crystals in the synovial fluid from an arthrocentesis confirms the diagnosis. First line treatment are NSAIDs. Indomethacin has traditionally been the NSAID of choice, but any NSAID can be used with similar efficacy.

Ethanol metabolism blocks renal excretion of uric acid which increases the risk for developing gouty arthritis. However, allopurinol is not contraindicated in individuals who consume ethanol (B). Hyperuricemia (C) is present (usually >8 mg/dL) in the gout patient, and when symptomatic, these patients should be treated. Colchicine (D) can be used in combination with allopurinol to help decrease the likelihood of a gouty flare while the uric acid level is decreasing after an acute attack has subsided. Colchicine decreases inflammation associated with lactic acid production and phagocytosis of urate; it terminates most gouty attacks within 6 to 12 hours but is limited by GI side effects.

Gout

• Patient will be a middle-aged man
• Complaining of acute onset of pain in the first MTP (Podagra)
• Labs will show needle-shaped crystal with negative birefringence
• Most commonly caused by uric acid crystals
• Treatment is:
  • Acute: NSAIDs, steroids, colchicine 
  • Chronic: allopurinol or colchicine
• Comments: Can be triggered by loop and thiazide diuretics

The correct answer is disseminated gonorrhea. The skin lesions above are hemorrhagic pustules which are essentially pathognomonic for gonorrhea.

The correct answer is admission and ortho consult. While this patient’s arthrocentesis is consistent with pseudogout due to the presence of rhomboid crystals, this can certainly occur in conjunction with a septic arthritis. In fact, gout and pseudogout patients are at higher risk for bacterial infection of their joints.

The correct answer is anserine bursitis. The anserine bursa is located on the medial aspect of the knee 2-3 inches below the joint, and can become inflamed due to trauma, gout, or repeated stress. Treatment is generally conservative with rest, ice, elevation, and NSAIDS.

The correct answer is slipped capital femoral epiphysis. A Klein line is a line drawn on an AP film along the superior aspect of the femoral neck.  It should pass through a portion of the femoral head.  If it does not, this is consistent with SCFE.

The correct answer is positively birefringent crystals. This x-ray demonstrates chondrocalcinosis, or calcium deposition in the joint space, diagnostic of pseudogout (calcium pyrophosphate crystals). Negatively birefringent crystals are caused by uric acid crystals in gout. Fat globules can be seen in fractures, and an elevated WBC count would be expected in a septic joint. This is certainly possible in this patient as any gouty arthritis increases the risk for septic joint, however the more likely finding is calcium pyrophosphate crystals.

This patient’s mechanism of injury as well as the significant ligamentous laxity is concerning for a knee dislocation.  CT angiography should be performed to rule out a popliteal artery injury.