Females are two to four times more likely to sustain an overuse running injury. The hip joint is involved in many of these injuries and can lead to conditions including iliotibial tract friction syndrome, gluteus medius insertional tendinopathy, and hip flexor tendinopathy. The main structures involved in these injuries all originate at the hip joint, however, as the lower extremity is a connected network of bone, muscle and ligaments, the knee and ankle have a role in these injury mechanics. Studies show that there are sex and age differences in the biomechanics of the legs during the running stride. This study was designed to investigate differences in the hip, knee, and ankle angles and moments between pre-and post-pubescent male and female athletes during the stance phase of the running stride. Research has suggested that increased maximum hip adduction, knee internal rotation, and knee flexion angles, along with hip abduction, knee external rotation, and ankle inversion moments, are related to iliotibial band friction syndrome; increased maximum hip adduction and angle of contact for hip adduction and knee abduction are related to gluteus medius insertional tendinopathy; and finally; that increased hip internal/external rotation plays a role in hip flexor tendinopathy. Court and field athletes (female = 69, male = 52) were recruited from local youth sport programs and Acadia university varsity athletics. The participants were further categorized as 34 pre-pubescent females (age = 10.88 yr ± 1.53, height = 149.12 cm ± 9.55, weight = 39.32 kg ± 8.14), 35 post-pubescent females (age = 20.40 yr ± 1.22, height = 169.10 cm ± 6.55, weight = 70.01 kg ± 10.81), 30 pre-pubescent males (age = 10.63 yr ±1.70 , height = 147.76 cm ± 14.09, weight = 40.30 kg ± 11.05), and 22 post-pubescent males (age = 20.77 ± 2.37 yr, height = 181.54 cm ± 6.34, weight = 81.53 kg ± 6.87). A 12-camera motion capture system and threeforce plates were used to capture lower extremity joint kinetic and kinematic data during a running protocol. This protocol was taken from a comprehensive protocol developed in the John MacIntyre motion Laboratory of Applied Biomechanics (mLAB). A two-way ANOVA was used to test for a between group (male vs. female), a within group (pre-pubescent vs. post-pubescent), and an interaction (sex by age) effect for the hip, knee, and ankle joint angles and moments. Overall, females displayed greater maximum angles for hip adduction, knee flexion, ankle eversion, ankle dorsiflexion, dorsiflexion angle at contact and greater maximum hip abduction moments. Pre-pubescent individuals also displayed greater maximum angles for knee adduction, knee flexion, and ankle eversion and greater knee adduction/abduction and ankle toe in/toe out angles at contact, as well as greater maximum ankle inversion moments. Relating these results to overuse injuries, we can suggest that iliotibial band friction can be related to increased hip adduction angles and hip abduction moments and that gluteus medius insertional tendinopathy can be related to increased hip adduction angles. These findings provide insight into the sex bias of these injuries and suggest that lower limb biomechanics may have a role in mechanism of injury.