 The vastus medialis is one of a group of muscles called quadriceps, which are located in the anterior compartment of the thigh. The other muscles of the group being vastus lateralis, rectus femoris, and deep rectus femoris is vastus intermedius. The muscles of the quadriceps converge distally onto the quadriceps tendon and then insert via the patella onto the tibial tuberosity. The vastus medialis takes its origin from the medial part of the intertrochanteric line, round onto the posterior aspect of the shaft of the femur, down the medial lip of the linear aspera, and onto the medial supracondyle line. The fibres of the vastus medialis wrap around the medial part of the thigh and insert, as we've said, onto the quadriceps tendon and the medial patella retinaculum. By convention, the vastus medialis is divided into two portions, a proximal longest part and an oblique part distally. Whether these two parts are in fact separate muscles is a matter of some controversy. What is beyond dispute, however, is that the angle of the muscle fibres with respect to the femoral axis changes down the length of the muscle, with the most distal fibres being almost horizontal. The oblique angulation of the distal VMO fibres means that they can exert a medial pull on the patella during forced extension of the knee, preventing lateral excursion of the patella that might otherwise occur due to the pull of the quadriceps and the q-angle of the junction of the tibia and femur. VMO insufficiency is thought to be implicated in patella femoral pain syndrome, a very common complaint in young active individuals that can result from patella maltracking. One of our earlier studies found evidence that the VMO fibre angle and the insertion level, that's to say how far down the medial border of the patella the muscle inserts, can be affected by the activity level of the individual. In this study we set out to quantify those differences by investigating two different populations with distinctly different activity levels. Although it is now recognised that there can be other drivers of patella femoral pain other than the VMO, there is still uncertainty surrounding the VMO's exact role. For example, recent literature has moved away from investigating false generation and instead has focused on timing of firing relative to the vastus lateralis. The results, however, are inconclusive and verbocomplicated by the presence of VMO delay in many healthy subjects. Fitting with the decades of inconclusive literature on VMO training and patella femoral pain, use of VMO exercises have come in and out of vogue and clinical practice. The type of exercises and exercise dosages become more sophisticated over time, but there is still a complexity of clarity on what VMO exercise is actually doing and who can be identified as suitable candidates for it. We are going to measure the subjects, VMO's biographical and exertional awareness rightly. Make sure the subjects are positioned super high on the bed and stabilise the distal length switch today. First, we'll start off by palpating the medial lateral borders of the patella and also the apex and the superior border and mark on the pen, apex and superior border. We'll work at the midpoint of the patella using the digital calibers and mark this on. Next, we'll feel for the subject's aces and using the metal ruler draw a line through the midpoint of the patella and this corresponds to the femoral axis. So using the ultrasound probe, we scan to find the subjects, muscle belly, you can see it here on the screen, as it inserts onto the femur. Once we find this, we rotate the probe, muscle fibres can be seen here horizontally across the screen. Once we find this point, freeze the screen and then mark on the midpoint of the ultrasound probe on either side. We then rotate the probe back to be perpendicular to the femoral axis. Unfreeze the screen and move the probe down and you can't see any of the muscle belly inserting onto the patella. We then mark this point again and we've finished the ultrasound machine. Then draw through the two marked either side of the fibremole and follow this line down so that it transects the femoral axis. Then draw a line through the point where we couldn't see the muscle fibres. to work out the insertion level. Then we use the protractor to work out the fibremole. So you can see in this patient the fibremole is 50 degrees. And then we calculate the length of the patella using the calipers. 48.62 millimetres and the insertion level is 17.58 millimetres. Our results show that the mean VMO fibre angle for the athletic group is 67.8 degrees and for the sedentary group 53.6 degrees and this result was highly statistically significant. The insertion ratio for the athletic group was 43% and for the sedentary group 39.5%. Although the athletic group had a higher mean insertion ratio, the result was not found to be statistically significant. When VMO angle is plotted against Tegna score there is found to be a high degree of correlation. Though this correlation is not seen when the insertion ratio is plotted against Tegna score. This diagram represents the relative angle and insertion ratio in sedentary and athletic study groups. The sedentary study group is shown in red and the athletic group in blue. Our investigation creates a new fresh perspective that the benefits gained from VMO training may in fact arise from changes in muscle architecture and not necessarily forced generation or timing. Furthermore it stimulates a new line of inquiry and that is prediction of who may be the most suitable candidates for VMO work. Given the prevalence of patella femoral pain and the economic burden in primary care, our team will be continuing this work in order to try and answer these more sophisticated but highly clinically relevant questions.