Variability of unilateral and bilateral isometric muscle strength of lower extremities extensors in young females and males

BACKGROUND

The muscle strength of the lower extremity extensors can be evaluated in the closed kinetic chain (CKC) during unilateral or bilateral conditions. Factors such as the mass and length of the muscle, joint angle, type of contraction, and gender influence the magnitude of the muscle strength. The aim of this study was to compare the isometric strength of lower extremity extensors between the different knee extension angles (KEs) as well as between bilateral and unilateral conditions.

METHODS

Nineteen female students (age: 20.2 ± 0.6 years) and nineteen male students (age: 20.3 ± 0.7 years) participated in the study. The muscle strength was evaluated in CKC using the strain gauge dynamometer. The analysis included values of the maximum muscle strength normalized to body mass (MS/BM) for the six KEs of 80°, 70°, 60°, 50°, 40° and 30°.

RESULTS

A significant main effect in the MS/BM values for the angle factor (p < 0.001) and condition factor (p < 0.001) was found. Moreover, there was a non-significant interaction effect between the angle factor and gender factor (p = 0.476) as well as between the condition factor and gender factor (p = 0.770). Comparisons showed significant differences in the MS/BM values between the six KEs (p < 0.001). Furthermore, significantly lower MS/BM values for bilateral conditions than unilateral conditions at the 30° KE were observed (p < 0.001).

CONCLUSION

The decrease in KE by 10° significantly increased the muscle strength of the lower extremity extensors. Gender did not affect the change in MS/BM values with the change in KE and conditions. Findings also revealed significant bilateral deficit, i.e., significantly a lower summed muscle strength during bilateral conditions than unilateral conditions. The study emphasized the importance of selecting the 30° KE as the optimal angle to assess the maximum strength developed in CKC.

Examination of the correlation between the knee extension angles in the sitting and supine positions measured using ImageJ software: a prospective cross-sectional study

[Purpose] We aimed to examine the correlation between the knee extension angles in the sitting and supine positions measured using ImageJ software. [Participants and Methods] A total of 50 legs in 25 healthy participants (17 males and 8 females) were included in our study. The knee extension angle was measured in the sitting and supine positions with the participants actively and maximally extending their knee joint on one side. The participants were photographed from the side with their knees centered in the image. Thereafter, the photographs were imported into the ImageJ image processing software to calculate the knee extension angles. [Results] The mean values of the knee extension angles in the sitting and supine positions were 131.5 ± 11.2° and 132.1 ± 12.2°, respectively, with a correlation coefficient of 0.85. No systematic errors were observed, and the minimal detectable change was 12.9°. [Conclusion] The knee extension angle in the sitting position showed a strong correlation with that in the supine position, with no systematic errors observed. Therefore, measurement of the knee extension angle in the sitting position can be an alternative to its measurement in the supine position.

Efficacy of posterior capsular release for flexion contracture in posterior-stabilized total knee arthroplasty

Purpose

Posterior capsular contracture causes stiffness during knee extension in knee osteoarthritis. Furthermore, in posterior-stabilized total knee arthroplasty (PS-TKA), a unique design such as the cam mechanism could conflict with the posterior capsule (PC) causing flexion contracture (FC). However, few studies have focused on the anatomical aspects of the PC. This study aimed to investigate the anatomical site and forms of posterior capsular attachment to the femoral cortex, and to evaluate the efficacy of posterior capsular release for FC by assessing changes in knee extension angles using a navigation system.

Methods

Attachment sites of the PC were investigated in 10 cadaveric knees using computed tomography. PS-TKA was performed in six cadaveric knees using a navigation system to evaluate the efficacy of posterior capsular release for FC. Posterior capsular release was performed stepwise at each part of the femoral condyle.

Results

The gastrocnemius tendon and PC were integrally attached to the femoral cortex at the medial and lateral condyles, whereas the PC at the intercondylar fossa was independently attached directly to the femoral cortex. Moreover, the PC at the intercondylar fossa was attached most distally among each femoral condyle. Posterior capsular release at the intercondylar fossa allowed 11.4° ± 2.8° improvement in knee extension. This angle was further improved by 5.5° ± 1.3°, after subsequent capsular release at the medial and lateral condyles.

Conclusion

The forms and sites of posterior capsular attachment differed based on the part of the femoral condyle. Stepwise posterior capsular release was effective for FC in PS-TKA.

Level of evidence

III.

Acute influence of restricted ankle dorsiflexion angle on knee joint mechanics during gait

BACKGROUND

Restrictions in range of ankle dorsiflexion (DF) motion can persist following ankle injuries. Ankle DF is necessary during terminal stance of gait, and its restricted range may affect knee joint kinematics and kinetics. The purpose of this study was to investigate the acute influence of varied levels of restricted ankle DF on knee joint sagittal and frontal plane kinematics and kinetics during gait.

METHODS

Thirty healthy volunteers walked with a custom-designed ankle brace that restricted ankle DF. Kinematics and kinetics were collected using a 7-camera motion analysis system and two force plates. Ankle dorsiflexion was restricted in 10-degree increments, allowing for four conditions: Free, light (LR), moderate (MR) and severe restriction (SR). Knee angles and moments were measured during terminal stance.

RESULTS

Real peak ankle DF for Free, LR, MR, and SR were 13.7±4.8°, 11.6±5.0°, 7.5±5.3°, and 4.2±7.2°, respectively. Peak knee extension angles under the same conditions were -6.7±6.7°, -5.4±6.4°, -2.5±7.5°, and 0.6±7.8°, respectively, and the peak knee varus moment was 0.48±0.17 Nm/kg, 0.47±0.17 Nm/kg, 0.53±0.20 Nm/kg, and 0.57±0.20 Nm/kg. The knee varus moment was significantly increased from MR condition with an 8-degree restriction in ankle DF.

CONCLUSION

Knee joint kinematics and kinetics in the sagittal and frontal planes were affected by reduced ankle DF during terminal stance of gait. Differences were observed with restriction in ankle DF range of approximately 8°.

LEVEL OF EVIDENCE

level III.