Baker's Cysts in Calcium Pyrophosphate Dihydrate Deposition Disease: A Musculoskeletal Ultrasound Study

Abstract

To investigate the clinical presentation of Baker's cyst in patients with calcium pyrophosphate dehydrate (CPPD) calcifications of the knee, the most commonly affected site in CPPD deposition disease, with the use of high-resolution musculoskeletal ultrasound (MUS). This was a prospective clinical and MUS study conducted in 60 patients with CPPD deposition disease of the knee. The patients' synovial fluid was aspirated and examined for the identification of crystals. The relationships between the Baker's cyst and occurrence of joint effusion, synovitis, chondrocalcinosis, and osteophytes were analyzed. Baker's cysts were demonstrated by MUS in 17 (28.3%) of the 60 patients. Joint effusion was present in all 60 (100%) patients. In addition, 55 (91.7%) patients had synovitis, 11 (18.3%) had chondrocarcinosis, and 45 (75.0%) had osteophytes. There was no significant correlation between the occurrence of Baker's cyst and the occurrence of effusion, synovitis, chondrocarcinosis, and osteophytes (p＞0.05). These results indicate that Baker's cysts are a common occurrence in patients with CPPD deposition disease, affecting 28% of this population and that they can be accompanied by joint effusion, synovitis, chondrocalcinosis, and osteophytes. Baker's cysts are easily missed on clinical examination without image guidance, but can be accurately identified with the use of MUS. Therefore, MUS should be more widely employed by clinicians in the diagnosis of Baker's cysts.