Measurement method of patellar tendon thickness with ultrasonography (long-axis image). Thickness is defined as the distance from the superficial to the deep layers of the tendon, measure at: (1) the proximal part: the point where the deep layer of the tendon is attached to the lower end of the patella; (2) the midpoint between the proximal and distal parts; and (3) the distal part: the point where the deep layer of the tendon is attached to the tibial tubercle. All schemes followed the same formatting.