The Impact of a Competitive Season on Patellar Tendon Stiffness in Division I Female Athletes

Background and/or Objectives: Shear wave elastography is an ultrasound technique used to quantify tissue stiffness. Despite its growing application in musculoskeletal research, limited studies have examined its ability to track changes in patellar tendon (PT) stiffness over time. The PT is vital in force transmission during jumping, sprinting, and cutting movements, making it susceptible to stress-related adaptations or injury in athletes. Monitoring PT stiffness over a competitive season may provide insights into tendon health, adaptation, and potential injury risk. This study investigates PT stiffness changes across a fall sports season in Division I collegiate female athletes, revealing potential adaptations or stress-related changes in tendon properties.

Design: Longitudinal observational study

Setting : Laboratory

Participants : Forty-eight Division I female athletes

Interventions: N/a

Main Outcome Measures: Longitudinal SWE ultrasound imaging was conducted bilaterally on the infrapatellar tendon at 20 degrees of knee flexion. Measurements were obtained pre-season and post-season. A software program analyzed mean and standard deviation stiffness of the PT distal to the patella. Paired samples t-tests were conducted to assess seasonal changes in PT stiffness for each leg. Additionally, a limb symmetry index was calculated to examine potential asymmetry in tendon adaptation.

Results: Results indicated a significant reduction in mean PT stiffness in the non-dominant leg from pre-season to post-season (p=0.012; pre=113.4±34.1 kPa, post=101.5±34.5 kPa). However, no significant changes were observed in the dominant leg (p=0.43; pre=119.6±39.0 kPa, post=115.4±32.6 kPa).

Conclusions: These findings suggest sports participation may induce localized adaptations in PT stiffness, potentially influenced by limb dominance, movement patterns, or training loads. Lower PT stiffness has been linked to healthier tendon tissue, while increased stiffness is associated with tendinopathic changes. Future studies should explore the clinical relevance of SWE-detected stiffness changes, particularly regarding injury risk, performance, and rehabilitation. Additionally, research should extend to non-healthy populations to determine if SWE can identify pathological tendon changes, aiding early diagnosis and targeted interventions for tendon disorders.