Effect of abduction and external rotation of the hip joint on muscle onset time during prone hip extension with knee flexion.

[Purpose] This study investigated the effect of hip position on muscle onset time during prone hip extension with knee flexion. [Subjects] The study included 21 healthy male volunteers. [Methods] Muscle onset times of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during right hip extension with knee flexion in the prone position. Measurements were made with the hip in 3 positions: (1) neutral, (2) abduction, and (3) abduction and external rotation. [Results] Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and with hip abduction and external rotation compared with that with the hip in the neutral position. Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and external rotation compared with that with hip abduction. The bilateral multifidus and left lumbar erector spinae onset times relative to the hamstrings were significantly earlier with hip abduction and external rotation compared with those with hip abduction and with the hip in the neutral position. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion is effective for advancing the onset times of the gluteus maximus, bilateral multifidus, and contralateral lumbar erector spinae.

Influence of Hip Joint Position on Muscle Activity during Prone Hip Extension with Knee Flexion.

[Purpose] This study investigated the selective activation of the gluteus maximus during a prone hip extension with knee flexion exercise, with the hip joint in different positions. [Subjects] The subjects were 21 healthy, male volunteers. [Methods] Activities of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during a prone hip extension with knee flexion exercise. Measurements were made with the hip joint in each of 3 positions: (1) a neutral hip joint position, (2) an abduction hip joint position, and (3) an abduction with external rotation hip joint position. [Results] Gluteus maximus activity was significantly higher when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. Gluteus maximus activity was also significantly higher in the abduction hip joint position than in the neutral hip joint position. Hamstring activity was significantly lower when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion exercise selectively activates the gluteus maximus.

Flexion Gap Measured in 45 Degrees and 90 Degrees of Hip Flexion Positions during Total Knee Arthroplasty: Measurement by Navigation System.

PURPOSE: To evaluate the influence of thigh weight in different hip flexion positions on the knee flexion gap in total knee arthroplasty (TKA). MATERIALS AND METHODS: We evaluated 20 patients (25 knees) with osteoarthritis of the knee that underwent TKA using a navigation system from May 2010 to April 2011. After posterior cruciate ligament sacrificing, complete soft tissue balancing, and fixation of all components with cement, the flexion gaps were measured with the patello-femoral joint reduced. Medial and lateral flexion gaps were measured separately in both the 90°-90° and 45°-90° flexion positions of the hip-knee joints. RESULTS: The medial and lateral flexion gaps in the 45°-90° flexion position of the hip-knee joints were 13.02±2.17 mm and 13.12±2.21 mm, respectively. The medial and lateral flexion gaps in the 90°-90° flexion position were 12.92±2.03 mm and 13.08±2.29 mm, respectively. The flexion gaps showed no significant (p>0.05) differences between the two different hip flexion positions. CONCLUSIONS: Flexion gaps in TKA were not influenced by hip flexion positions (45° or 90° of flexion). Therefore, soft tissue balancing and polyethylene thickness should not be affected by hip flexion positions during TKA.

Flexion Gap Measured in 45 Degrees and 90 Degrees of Hip Flexion Positions during Total Knee Arthroplasty: Measurement by Navigation System

PURPOSE: To evaluate the influence of thigh weight in different hip flexion positions on the knee flexion gap in total knee arthroplasty (TKA). MATERIALS AND METHODS: We evaluated 20 patients (25 knees) with osteoarthritis of the knee that underwent TKA using a navigation system from May 2010 to April 2011. After posterior cruciate ligament sacrificing, complete soft tissue balancing, and fixation of all components with cement, the flexion gaps were measured with the patello-femoral joint reduced. Medial and lateral flexion gaps were measured separately in both the 90degrees-90degrees and 45degrees-90degrees flexion positions of the hip-knee joints. RESULTS: The medial and lateral flexion gaps in the 45degrees-90degrees flexion position of the hip-knee joints were 13.02+/-2.17 mm and 13.12+/-2.21 mm, respectively. The medial and lateral flexion gaps in the 90degrees-90degrees flexion position were 12.92+/-2.03 mm and 13.08+/-2.29 mm, respectively. The flexion gaps showed no significant (p>0.05) differences between the two different hip flexion positions. CONCLUSIONS: Flexion gaps in TKA were not influenced by hip flexion positions (45degrees or 90degrees of flexion). Therefore, soft tissue balancing and polyethylene thickness should not be affected by hip flexion positions during TKA.