Cross-sectional Study of the Hip Joint Condition in Young Baseball Players

OBJECTIVE: The hip joint is a crucial part of the kinetic chain for throwing baseball pitches. Nevertheless, few reports have described assessments of the functional development of the hip joint in young baseball players. METHODS: We examined 315 young baseball players, 7–14 years old, all of whom had completed a self-administered questionnaire including items related to the dominant side and throwing-related hip joint pain sustained during the previous year. We measured the hip ranges of motion (ROMs: external and internal rotation and flexion) and hip muscle strengths (external and internal rotation) on the dominant and non-dominant sides. The differences of hip ROMs and muscle strengths between the dominant and non-dominant sides and between age groups were investigated. Correlations were calculated between the players ages and hip ROMs and muscle strengths. RESULTS: No baseball player reported hip pain. The hip external rotation on the dominant side was smaller than that on the non-dominant side, whereas the hip internal rotation on the dominant side was greater than that on the non-dominant side. However, no significant difference was found between the dominant and non-dominant sides in terms of the hip muscle strength. Significant positive associations were found between the player’s age and hip muscle strengths, whereas significant negative associations were found between the age and hip ROMs. CONCLUSIONS: Our data concerning the relationship between age and hip joint development could be useful for supporting strategies for the prevention and rehabilitation of throwing injuries; however, hip injuries might be rare among young baseball players.