A 75-year-old woman presents with acute pain and swelling in the left knee. On examination the left knee is hot and tender with moderate synovial fluid collection. Radiograph of the right knee shows calcification of the meniscus.
Synovial fluid was sterile on culture and rhomboid shaped crystals were identified on microscopy of the fluid.
Which of the following statements about this condition is NOT true?
A. Narrowing of the joint space is often present
B. The symphysis pubis is one of many other joints that can be affected by this disorder
C. Serum calcium levels may be elevated in some patients
D. Negatively birefringent crystals may be identified on synovial fluid analysis
E. There may be large subchondral cysts
Correct answer: D
This patient presents with acute monoarthritis of the right knee. The clinical picture and the radiological findings are suggestive of pseudogout and calcium pyrophosphate deposition (CPPD), which is characterised by the presence of positively birefringent crystals on synovial fluid analysis (negatively birefringent ones are found in gout).
The knee is the most common site affected by this disorder. Other locations include: the triangular fibrocartilage of the wrist sacroiliac joints symphysis pubis the glenoid of the shoulder the labrum of the hip the elbow the ankle acromioclavicular joint.
CPPD is associated with hemochromatosis, primary hyperparathyroidism, hypothyroidism, and hypomagnesemia. Other findings include joint space narrowing, large subchondral cysts and many intra-articular bodies from subchondral bone fragmentation.