Ultrasound imaging for the rheumatologist XXIX. Sonographic assessment of the knee in patients with osteoarthritis.

OBJECTIVES

To investigate the prevalence and severity of sonographic-detected abnormalities in knee osteoarthritis (OA) and to correlate ultrasound (US) findings with clinical data.

METHODS

Outpatients with chronic, painful knee OA according to the ACR criteria were consecutively recruited and underwent clinical and US examinations. An expert rheumatologist recorded the presence of knee joint pain, swelling and tenderness, patient's global assessment of knee pain using visual analogue scale (VAS), and Lequesne Index of severity for knee OA. A second rheumatologist, blinded to the clinical data, performed the knee US examination using a Logiq9 machine equipped with a 12MHz linear probe and registering the presence of joint effusion, synovial proliferation, power Doppler (PD) signal, Baker's cyst, osteophytes and femoral cartilage abnormalities.

RESULTS

One hundred and sixty-four knees of 82 patients (53 women, 29 men) were studied; mean age was 63.2±8.1 SD years, mean disease duration was 4.3±5.6 SD years. All patients complained of at least one knee joint pain during physical activity. Mean patient's VAS for knee pain was 48.4±19.9 SD mm, mean Lequesne Index was 8.2±4.4 SD. Knee swelling was present in 39% of the patients and tenderness was found in 65.8%. US showed: joint effusion in 43.3% of the patients, synovial proliferation in 22.1%, PD signal in 2.9%, Baker's cysts in 6.6%, cartilage abnormalities in 79%, osteophytes in 100%. In all patients US findings were present at least at the level of one knee. Statistically significant correlations were demonstrated between a composite inflammatory score and both VAS (p=0.004) and Lequesne Index (p<0.0001).

CONCLUSIONS

This US study showed both inflammatory abnormalities and structural damage lesions in knee OA. Interestingly, statistically significant correlations were demonstrated between US inflammatory findings and the main clinical tests for OA, confirming that sonography has a relevant role in the global evaluation of patients with knee OA.