The applicability of ultrasound imaging in the assessment of dynamic patella tracking: a preliminary investigation.

The purpose of the study was to examine the effect of muscle stimulation of the Vastus Medialis Oblique (VMO) and Vastus Laterialis (VL) muscles on patella position in-vivo assessed by ultrasound scanning. Also to assess the reliability of the technique used. The position of the patella was measured using B-Mode, real time ultrasonography prior to and following the electrical stimulation of the VMO and VL muscles in 10 asymptomatic subjects. Maximal (tetanic) contraction of VMO brought about a mean medially displacement of the patella of 6.8+/-2.9 mm and VL a mean lateral displacement of 5.6+/-2.7 mm. The between repetition variation of displacement generated on muscle stimulation was assessed, results demonstrating a strong correlation between repetitions r=0.85 and 0.87 (p<0.01), for medial and lateral displacement respectively. The stimulation of either muscle (VMO or VL) brought about a consistent movement of the patella either medially for VMO or laterally for VL again demonstrating the reliability of the technique. The study found the reliability of the ultrasound technique to be good, reflecting those of previous studies which have used ultrasound to assess patella position.