To determine clinical and sonographic factors associated with painful episodes in patients with knee osteoarthritis (OA).
In this cross-sectional controlled study, patients with primary knee OA (ACR criteria) were prospectively placed into two groups. Group A: 81 patients with knee pain during physical activity >or=30 mm in visual analogue scale (VAS) for pain for at least 48 h prior to inclusion; Group B: 20 patients without knee pain from at least 1 month prior to inclusion. Clinical parameters, knee radiographic and ultrasonographic findings were collected. The sonographic study assessed joint effusion in the suprapatellar pouch, infrapatellar superficial and deep bursitis, meniscal lesions, anserine tendinobursitis, and Baker's cyst.
Group A patients tended to be older and heavier women than group B (P<0.05). The most frequent radiographic stage was III (57%) in group A, and I (35%) and II (35%) in group B, showing differences in the distribution of each radiographic stage (P<0.005). The most frequent ultrasonographic finding in group A was suprapatellar effusion (79%), and in group B it was meniscal lesions (40%). Ultrasonographic findings showed in group A a significant increase of suprapatellar effusion (P<0.001) and a tendency towards an increase of Baker's cyst (P=0.06). Suprapatellar effusion, Baker's cyst, and body mass index (BMI) were the factors associated with the appearance of pain after the logistic regression analysis.
Suprapatellar effusion, Baker's cyst, and higher BMI are more frequent and seem to be risk factors of painful flare in OA of the knee.