Ultrasound examination of the knee is particularly useful in the detection of synovitis, early degenerative changes within the articular cartilage of the femoral condyles, calcifications within the articular cartilage layer and menisci, bursitis, and popliteal cysts. Also, important anatomical information about the structural integrity of the supporting tissues around the knee can be obtained by ultrasound in patients presenting with 'knee pain'. We review the available evidence about the use of ultrasound in knee examination, provide information on the technical equipment and scanning methods and discuss the still controversial issues.