Assessment of knee osteoarthritis by ultrasonography and its association with knee pain

BACKGROUND: Pain is a significant cause of disability in knee osteoarthritis. Conventional radiography is widely used in the assessment of knee osteoarthritis, however radiographic findings do not correlate well with pain. Ultrasonography can be used to evaluate the soft tissue structures of the knee that can be related to pain. OBJECTIVE: To evaluate pain-related soft tissue structures of the knee with ultrasonography. METHODS: This cross-sectional study included a total of 198 knees from 99 patients with knee osteoarthritis. Knee pain and functional status were evaluated by performing visual analogue scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). On the ultrasound, cartilaginous thickness, knee effusion and presence of Baker's cyst were assessed and the correlation to pain was investigated. RESULTS: Baker's cyst was significantly more frequent in symptomatic knees (13.9%) compared to asymptomatic knees (2.5%). Patients with Baker's cyst had a significantly more limited degree of knee flexion, significantly higher resting VAS pain scores and worse WOMAC scores compared to patients without Baker's cyst. In log-linear analysis, presence of Baker's cyst increased the risk of pain by 2.94 times. CONCLUSION: Ultrasound as a modality that is easily accessible, inexpensive and without radiation exposure is helpful to demonstrate factors related to pain in knee osteoarthritis by allowing assessment of soft tissue structures.