Muscle size-scaled shear elastic modulus: A muscle force index independent of maximal voluntary contraction, assessed during elbow extension

Effect of soft tissue tension around the knee joint on medio-lateral patellar position

Patellofemoral pain (PFP) is one of the most common sports injuries of the knee joint and has a high persistence and recurrence rate. Medio-lateral patellar position in the knee extension position during contraction is associated with PFP. However, soft tissue tension that most influences the medio-lateral patellar position in the knee extension position during contraction in vivo is unclear. We aimed to clarify the relationship between medio-lateral patellar position and soft tissue tension around the knee joint. Twelve patients with PFP and 20 healthy participants were included. Medio-lateral patellar position and tension of the rectus femoris, vastus lateralis (VL), vastus medialis, iliotibial band (ITB), lateral patellofemoral ligament, and medial patellofemoral ligament were measured during contraction and rest. The tensions of the VL and ITB during contraction and the medio-lateral patellar position at rest were significantly associated with medio-lateral patellar position during contraction (β = 0.449, 0.354, and 0.393, respectively). In addition, the tension of ITB was significantly associated with the medio-lateral patellar position at rest (β = 0.646). These relationships were not affected by the presence of PFP. These findings suggest that the patellar position during contraction became more lateral as the tension in the VL and ITB increased, regardless of the presence of PFP. These results may facilitate the prevention and treatment of PFP.

Effective Stretching Positions of the Piriformis Muscle Evaluated Using Shear Wave Elastography

CONTEXT

Piriformis syndrome is often associated with muscle spasms and shortening of the piriformis muscle (PM). Physical therapy, including static stretching of the PM, is one of the treatments for this syndrome. However, the effective stretching position of the PM is unclear in vivo. This study aimed to determine the effective stretching positions of the PM using ultrasonic shear wave elastography.

DESIGN

Observational study.

METHODS

Twenty-one healthy young men (22.7 [2.4] y) participated in this study. The shear elastic modulus of the PM was measured at 12 stretching positions using shear wave elastography. Three of the 12 positions were tested with maximum internal rotation at 0°, 20°, or 40° hip adduction in 90° hip flexion. Nine of the 12 positions were tested with maximum external rotation at positions combined with 3 hip-flexion angles (70°, 90°, and 110°) and 3 hip-adduction angles (0°, 20°, and 40°).

RESULTS

The shear elastic modulus of the PM was significantly higher in the order of 40°, 20°, and 0° of adduction and higher in external rotation than in internal rotation. The shear elastic modulus of the PM was significantly greater in combined 110° hip flexion and 40° adduction with maximum external rotation than in all other positions.

CONCLUSION

This study revealed that the position in which the PM was most stretched was maximum external rotation with 110° hip flexion and 40° hip adduction.

Relationship between individual forces of each quadriceps head during low-load knee extension and cartilage thickness and knee pain in women with knee osteoarthritis

BACKGROUND

This study aimed to clarify the individual forces of each quadriceps head during low-load contractions and to determine the associations between individual muscle force and cartilage thickness and symptoms in female knee osteoarthritis patients.

METHODS

Twenty-two women with painful knee osteoarthritis and 15 asymptomatic age-matched women (control group) participated in this cross-sectional study. Maximal knee extension strength and the cross-sectional area of each quadriceps muscle were measured. Shear modulus was calculated for each muscle during 20-Nm torque production by shear-wave elastography. Muscle force index was defined as the product of the cross-sectional area and shear modulus. Medial femur cartilage thickness was measured using an ultrasound B-mode image. Knee pain during gait was evaluated using a Numerical Rating Scale. Muscle force index, cross-sectional area, and maximal knee extension strength, which were defined as muscle functions, were compared between groups using the unpaired t-test. Correlation coefficients were calculated using muscle function, cartilage thickness, or pain.

FINDINGS

Maximal strength and vastus lateralis force index were smaller in the knee osteoarthritis group than in the control group (p < 0.001 and p = 0.005, respectively). In the knee osteoarthritis group, vastus medialis and vastus lateralis force indexes were positively correlated with cartilage thickness (r = 0.57 and r = 0.45, respectively), whereas the rectus femoris force index was negatively correlated with cartilage thickness (r = -0.45). The vastus lateralis force index was negatively correlated with knee pain (ρ = -0.56).

INTERPRETATION

Vasti force indices were positively associated with cartilage thickness; however, rectus femoris index was negatively associated in female patients with knee osteoarthritis.