Sailly, Whiteley & Johnson (2013) Doppler ultrasound and tibial tuberosity maturation status predicts pain in adolescent male athletes with Osgood-Schlatter's disease: a case series with comparison group and clinical interpretation

Background The pathogenesis of the Osgood-Schlatter's disease (OSD) is still debated. The fragmentation of the ossification centre has been questioned as a definitive sign of OSD and has been seen as a normal development of the anterior tibial tubercle (ATT).
Objectives It is unknown if such changes are present in the presumed pathological tendon insertion seen in OSD, nor the relation of Doppler-positive changes to pain on clinical examination.
Methods A prospective analysis was carried out on 20 consecutive symptomatic male athletes (13.9 years±1.3) and a comparison group of asymptomatic subjects. All underwent a comparative clinical assessment and ultrasound with colour Doppler scan on both knees. Subjective pain was recorded with a visual analogue scale (VAS) during provocative manoeuvres: palpation, resisted contraction and single leg squat.
Results Positive Doppler US (within the distal end of the patellar tendon) was associated with higher pain on palpation (47±24.5 vs 18±11.4, p<0.01) and resisted static contraction (59±20.2 vs 27±12.5, p<0.001) compared with Doppler-negative subjects. No Doppler activity was found in the comparison group. VAS for palpation and resisted contraction of the athletes graded as stage 2 (51.1±22.0 and 60.0±21.2) were significantly higher than stage 3 (17.8±12.0 and 18.9±16.9) and stage 4 (15.0±7.1 and 25.0±7.1; p<0.01).
Conclusions More painful OSD is associated with the presence of neo-vessels. This may be linked with a particular stage of ATT maturation and applied compressive forces. A Doppler ultrasound scan adds practical information to develop the care plan of the patient.

Warden, Weatherholt, Gudeman, Mitchell, Thompson & Fuchs (2017) Progressive skeletal benefits of physical activity when young as assessed at the midshaft humerus in male baseball players.

Purpose The current study explored physical activity-induced bone adaptation at different stages of somatic maturity by comparing side-to-side differences in midshaft humerus properties between male throwing athletes and controls. Throwers present an internally controlled model, while inclusion of control subjects removes normal arm dominance influences.
Methods Throwing athletes (n=90) and controls (n=51) were categorized into maturity groups (PRE, PERI, POST-EARLY, POST-MID and POST-LATE) based on estimated years from peak height velocity (<−2, −2-to-2, 2-to-4, 4-to-10 and >10 years). Side-to-side percent differences in midshaft humerus cortical volumetric bone mineral density (Ct.vBMD) and bone mineral content (Ct.BMC), total (Tt.Ar), medullary (Me.Ar) and cortical (Ct.Ar) area, average cortical thickness (Ct.Th), and polar Strength Strain Index (SSIP) was assessed.
Results Significant interactions between physical activity and maturity on side-to-side differences in Ct.BMC, Tt.Ar, Ct.Ar, Me.Ar, Ct.Th and SSIP resulted from: 1) greater throwing-to-nonthrowing arm differences than dominant-to-nondominant arm differences in controls (all p<0.05), and; 2) throwing-to-nonthrowing arm differences in throwers being progressively greater across maturity groups (all p<0.05). Regional analyses revealed greatest adaptation in medial and lateral sectors, particularly in the three POST maturity groups. Years throwing predicted 59% of the variance of the variance in throwing-to-nonthrowing arm difference in SSIP (p<0.001).
Conclusion These data suggest physical activity has skeletal benefits beginning prior to and continuing beyond somatic maturation, and that a longer duration of exposure to physical activity has cumulative skeletal benefits. Thus, physical activity should be encouraged at the earliest age possible and be continued into early adulthood to optimize skeletal benefits

Bergeron, Mountjoy, Armstrong, Chia, Côté, Emery, Faigenbaum, Hall, Kriemler, Léglise & Malina (2015) International Olympic Committee consensus statement on youth athletic development

The health, fitness and other advantages of youth sports participation are well recognised. However, there are considerable challenges for all stakeholders involved—especially youth athletes—in trying to maintain inclusive, sustainable and enjoyable participation and success for all levels of individual athletic achievement. In an effort to advance a more unified, evidence-informed approach to youth athlete development, the IOC critically evaluated the current state of science and practice of youth athlete development and presented recommendations for developing healthy, resilient and capable youth athletes, while providing opportunities for all levels of sport participation and success. The IOC further challenges all youth and other sport governing bodies to embrace and implement these recommended guiding principles.

Tristan Chai