Author(s): HIKARI, T., HIDEYUKI, T., Institution: UNIVERSITY OF TSUKUBA, Country: JAPAN, Abstract-ID: 2646

INTRODUCTION:
Malalignment of the patellofemoral joint (PFJ), which may increase joint contact pressure, has been proposed as one contributing factor to patellofemoral pain syndrome (PFPS). However, it remains unclear whether PFJ malalignment is a cause or a consequence of PFPS. Understanding the relationship between thigh muscle stiffness and PFJ alignment in healthy athletes may help identify potential mechanical contributors to PFPS risk before symptom onset. This study aimed to investigate the relationship between shear wave velocity (SWV) of the lower limb muscles and PFJ alignment in healthy college athletes.
METHODS:
Sixty healthy college athletes who performed habitual exercise at least three times per week were recruited (30 males and 30 females; age: 20.2 ± 1.0 years; height: 167.5 ± 8.7 cm; weight: 62.6 ± 6.7 kg). Axial T1-weighted magnetic resonance images of the patellofemoral joint (PFJ) were acquired using an MRI system at 30° of knee flexion. The following indices were quantified to assess PFJ alignment: bisect offset index, patellar tilt angle (posterior condylar line; PCL-based) and patellar tilt angle (anterior intercondylar line; AIL-based). Shear wave velocity (SWV), as an index of tissue stiffness, was assessed using shear wave elastography with an ultrasound system. SWV was measured at 15 sites: iliotibial band (ITB), rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), vastus medialis (VM), gracilis (GR), sartorius (SA), adductor magnus (AM), adductor longus (AL), tensor fasciae latae (TFL), biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), gluteus medius (Gmed), and gluteus maximus (Gmax). Pearson’s correlation analyses were performed to examine the relationships between PFJ alignment indices and SWV of each thigh muscle.
RESULTS:
Significant positive correlations were observed between bisect offset index and SWV of the TFL (p = 0.031, r = 0.279). Significant positive correlations were found between patellar tilt angle (both PCL-based and AIL-based) and SWV of the Gmed (PCL-based: p = 0.005, r = 0.356; AIL-based: p = 0.018, r = 0.304). No significant correlations were identified between SWV of the other muscles and PFJ alignment indices.
CONCLUSION:
Anatomically, the TFL and Gmed are hip abductors and insert into the iliotibial band, which attaches to the lateral tibial condyle (Gerdy’s tubercle). Their tension can be transmitted to the tibia via the iliotibial band, and increased stiffness may influence rotational alignment at the knee, potentially promoting relative femoral internal rotation (i.e., tibial external rotation). Therefore, these findings suggest that stiffness of TFL and Gmed may be associated with increased patellar tilt angle and bisect offset index in healthy college athletes, which may be relevant to PFPS risk.