Moment arm of the patellar tendon in the human knee

Krevolin, Janet; Pandy, Marcus G.; Pearce, John C.

doi:10.1016/j.jbiomech.2003.09.010

Cited by 175 publications

(185 citation statements)

References 12 publications

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“…The knee flexiondirected forces from the biceps femoris during testing of knee extension were estimated by the amplitude of the electromyographic signal during testing and the relationship between flexion force and electromyographic signal amplitude. The measured knee extension torque was converted to tendon force using the following equation 25 : [tendon force = knee extension torque (agonist + antagonist)/ moment arm of the patellar tendon]; moment arm of the patellar tendon was estimated to be 44.7 mm based on the methodology developed by Krevolin et al 17 Tendon stiffness was defined as the slope of the tendon-length curve during the ascending phase of the MVIC test between 90% and 100% maximum force. 8 Prior to performing the 4 sets of eccentric knee extension exercises, participants were given 10 minutes of rest.…”

Section: Estimates Of Knee Movement and Coactivation Torquementioning

confidence: 99%

Increased Patellar Tendon Microcirculation and Reduction of Tendon Stiffness Following Knee Extension Eccentric Exercises

Yin

Chen

Wu³

et al. 2014

J Orthop Sports Phys Ther

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Tendons are fibrous connective tissues that are capable of transmitting mechanical loading and utilize elastic energy during locomotion. 29 Tendon adaptations to mechanical loads include changes in mechanical properties and metaboliccirculatory function. 11,13 Tendon mechanical properties determine stress and strain distribution within the tendon. 37,38,40 Tendon microcirculation reflects intratendinous metabolic demands and includes the distribution of blood flow and oxygen consumption in the arteriolar, capillary, and venular segments. 22,31Local blood flow is controlled by autoregulation (myogenic responses and metabolism) and shearing stress stimulation of the endothelium and neurohormones, 31 and is partially influenced by vessel radius and length (Poiseuille's equation). 5Viscoelastic behaviors of the vessels and tendons suggest that adaptation of tendon microcirculation during exercises may vary due to differences in tendons' plastic mechanical properties. 18,19,36 However, this theory has not been validated.Exercises involving movements that an individual is not used to and that reduce tendon stiffness, 26 as well as exercises that cause ischemia reperfusion, 1,21 are proposed as likely etiological factors in acute tendinopathies occurring when someone suddenly increases his or her level of physical activities ("weekend warrior" syndrome) or has eccentric exercise T T STUDY DESIGN: Controlled laboratory study. T T OBJECTIVES:To measure and compare patellar tendon stiffness and microcirculation in college tennis players and nonathletic students when performing eccentric knee extension exercises that do and do not reduce tendon stiffness. T T BACKGROUND:Previous studies suggest that tendon microcirculation response during exercises may vary based on the tendon's plastic properties. T T METHODS:The study included 3 groups of college-age male students: tennis players who performed 4 sets of either 40 (n = 12) or 80 (n = 13) repetitions of eccentric knee extension exercise and nonathletic students (n = 14) who performed 4 sets of 40 repetitions. Tendon stiffness was measured before and after exercise completion. Changes in total hemoglobin and oxygen saturation (OSat) were analyzed while performing the 4 sets. Comparisons were made within and between the groups. The level of association between tendon microcirculation and stiffness reduction was assessed. T T RESULTS:The 2 groups (player/4 × 80 and student/4 × 40) exhibiting patellar tendon stiffness reductions (P<.008) showed higher total hemoglobin and OSat levels, above the pre-exercise levels, in the fourth set compared to the first set of exercises (P<.004). The tennis players who performed 4 sets of 40 repetitions exhibited higher OSat levels in the fourth set than in the first set (P = .004) but had no reduction in tendon stiffness. Changes in OSat levels in the fourth set were correlated with patellar tendon stiffness reductions (r = -0.381, P = .02). T T CONCLUSION:We conclude that there was increased patellar tendon microcirculation after performing...

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Section: Estimates Of Knee Movement and Coactivation Torquementioning

confidence: 99%

Increased Patellar Tendon Microcirculation and Reduction of Tendon Stiffness Following Knee Extension Eccentric Exercises

Yin

Chen

Wu³

et al. 2014

J Orthop Sports Phys Ther

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“…Tendon force was calculated as F tend ¼ (P þ P antag )/T arm , where F tend ¼ force in the patellar tendon, P ¼ observed knee extensor torque output, P antag ¼ antagonistic (hamstring) cocontraction torque, and T arm ¼ patellar tendon moment arm 44.7 mm computed from the average of previous reports. 21,22 Estimation of Hamstring Cocontraction during Knee Extension Using Electromyographical (EMG) Activity The EMG of the long head of the biceps femoris muscle (BF) was measured in order to ascertain the level of antagonistic muscle cocontraction 16 during the isometric knee extension efforts. Assumptions were that BF is representative of its constituent muscle group, 23 and BF EMG relationship with knee flexors torque is generally linear.…”

Section: Measurement Of Patellar Tendon Forcesmentioning

confidence: 99%

Tendon structural and mechanical properties do not differ between genders in a healthy community‐dwelling elderly population

Burgess

Pearson

Breen

et al. 2009

Journal Orthopaedic Research

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Elderly women are reportedly at higher risk of falling than their male counterparts. Postural balance is highly associated with fall risk and is also correlated with tendon structural and mechanical properties. Gender differences in tendon properties could partly explain the discrepancy in fall risk. Thus the purpose of this study was to investigate the possible gender difference in tendon properties in the elderly. The properties of the patellar tendon of 55 elderly (men n ¼ 27, aged 72 AE 1 years, women n ¼ 28, aged 70 AE 1 years) participants were tested. Tendon stiffness (K), length (L), and cross-sectional area (CSA) were measured using B-mode ultrasonography, dynamometry, and electromyography during ramped isometric knee extensions. There were no significant differences ( p > 0.05) between men and women in tendon stiffness (elderly men 550.9 AE 29.2 vs. women 502.9 AE 44.9 Nmm À1 ) or in Young's modulus (elderly men 0.32 AE 0.02 vs. women 0.36 AE 0.04 GPa). This elderly group had similar tendon structural and mechanical properties. The comparable characteristics in genderspecific tendon properties in an elderly population exhibiting similar lifestyle characteristics to the current sample may not explain the reports in the literature regarding increased fall risk in elderly women relative to that seen in men of a similar age. Keywords: aging; gender differences; patellar tendon; stiffness; Young's modulusIn the last 30 years the proportion of the population aged 65 years or more has increased to 16% in the UK and this increase is set to continue (The Office for National Statistics, 2006). Approximately one-third of people aged over 65 fall at least once a year, and about half of these do so recurrently, leading to injury and subsequent decrease in quality of life, and in many cases death. 1 Elderly women exhibit a higher risk of falling than their male counterparts, 2,3 and most falls occur after a loss of stability in a forward direction such as tripping while walking. 2 In order to maintain balance individuals require information concerning the orientation of the body in space and the geometry of the body. In humans this information is obtained via the complex interactions of sensory systems (primarily the somatosensory, visual, and vestibular systems) and motor systems. 4 Aging results in a decline in the function of these systems and their interaction, which has been related to reduced balance ability and thus increased fall risk. [5][6][7]

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“…The patella acts as the lever arm in extensor arc motion and improves quadriceps strength by 30-50% [17]. Patella height alters the joint reaction force of the patellofemoral joint.…”

Section: Introductionmentioning

confidence: 99%

Novel method of measuring patellar height ratio using a distal femoral reference point

Chareancholvanich

Narkbunnam

2011

International Orthopaedics (SICOT)

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Purpose Patellar height is an important factor in patellar tracking and alters the force of the patellofemoral joint reaction. Several methods for measuring patellar height ratio have been described, with no single method recognised as a gold standard. This study developed a new measurement method using a distal femoral reference, where the normal values of measurement are unaffected by varying angles of knee flexion. Methods Eighty-five volunteers had radiographs taken of their knees at 0°, 15°, 30°, 45°and 60°of flexion in a supine position. Patellar height was assessed by five different measurement methods: Insall-Salvati (IS), modified InsallSalvati (MIS), Caton-Deschamps (CD), Blackburne-Peel (BP) and our new method. Three independent examiners sequentially conducted all measurements under identical conditions. Results The normal value obtained with the method reported here was 1 ± 0.1standard deviation (SD) (IS 1.1 ± 0.2, MIS 1.8 ± 0.25, CD 1.08 ± 0.2, BP 0.9 ± 0.2). IS and the new method tended to have better reliability in the face of varying knee-flexion angles than did CD, BP or MIS. All methods had good to excellent levels of interobserver variation (IS 0.969, new method 0.811, MIS 0.768, CD 0.735, BP 0.708). Conclusion The new patellar height ratio measurement method proved to be accurate and reproducible for evaluating a normal population. This method offered the benefit of using the distal femur as a reference landmark, and, thus, the resulting measurements were not altered by varying degrees of knee flexion.

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Moment arm of the patellar tendon in the human knee

Cited by 175 publications

References 12 publications

Increased Patellar Tendon Microcirculation and Reduction of Tendon Stiffness Following Knee Extension Eccentric Exercises

Increased Patellar Tendon Microcirculation and Reduction of Tendon Stiffness Following Knee Extension Eccentric Exercises

Tendon structural and mechanical properties do not differ between genders in a healthy community‐dwelling elderly population

Novel method of measuring patellar height ratio using a distal femoral reference point

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