Muscle-tendon structure and dimensions in adults and children

Muscle performance is closely related to the architecture and dimensions of the muscle-tendon unit and the effect of maturation on these architectural characteristics in humans is currently unknown. This study determined whether there are differences in musculo-tendinous architecture between adults and children of both sexes. Fascicle length and pennation angle were measured from ultrasound images at three sites along the length of the vastus intermedius, vastus lateralis, vastis medialis and rectus femoris muscles. Muscle volume and muscle-tendon length were measured from magnetic resonance images. Muscle physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume to optimum fascicle length. Fascicle length was greater in the adult groups than in children (P < 0.05) but pennation angle did not differ between groups (P > 0.05). The ratios between fascicle and muscle length and between fascicle and tendon length were not different (P > 0.05) between adults and children for any quadriceps muscle. Quadriceps volume and PCSA of each muscle were greater in adults than children (P < 0.01) but the relative proportion of each head to the total quadriceps volume was similar in all groups. However, the difference in PCSA between adults and children (men approximately 104% greater than boys, women approximately 57% greater than girls) was greater (P < 0.05) than the difference in fascicle length (men approximately 37% greater than boys, women approximately 10% greater than girls). It is concluded that the fascicle, muscle and tendon lengthen proportionally during maturation, thus the muscle-tendon stiffness and excursion range are likely to be similar in children and adults but the relatively greater increase in PCSA than fascicle length indicates that adult muscles are better designed for force production than children's muscles.

Mechanical properties of the patellar tendon in adults and children

It is not currently known how the mechanical properties of human tendons change with maturation in the two sexes. To address this, the stiffness and Young's modulus of the patellar tendon were measured in men, women, boys and girls (each group, n=10). Patellar tendon force (F(pt)) was calculated from the measured joint moment during a ramped voluntary isometric knee extension contraction, the antagonist knee extensor muscle co-activation quantified from its electromyographical activity, and the patellar tendon moment arm measured from magnetic resonance images. Tendon elongation was imaged using the sagittal-plane ultrasound scans throughout the contraction. Tendon cross-sectional area was measured at rest from ultrasound scans in the transverse plane. Maximal F(pt) and tendon elongation were (mean+/-SE) 5453+/-307 N and 5+/-0.5 mm for men, 3877+/-307 N and 4.9+/-0.6 mm for women, 2017+/-170 N and 6.2+/-0.5 mm for boys and 2169+/-182 N and 5.9+/-0.7 mm for girls. In all groups, tendon stiffness and Young's modulus were examined at the level that corresponded to the maximal 30% of the weakest participant's F(pt) and stress, respectively; these were 925-1321 N and 11.5-16.5 MPa, respectively. Stiffness was 94% greater in men than boys and 84% greater in women than girls (p<0.01), with no differences between men and women, or boys and girls (men 1076+/-87 N/mm; women 1030+/-139 N/mm; boys 555+/-71 N/mm and girls 561.5+/-57.4 N/mm). Young's modulus was 99% greater in men than boys (p<0.01), and 66% greater in women than girls (p<0.05). There were no differences in modulus between men and women, or boys and girls (men 597+/-49 MPa; women 549+/-70 MPa; boys 255+/-42 MPa and girls 302+/-33 MPa). These findings indicate that the mechanical stiffness of tendon increases with maturation due to an increased Young's modulus and, in females due to a greater increase in tendon cross-sectional area than tendon length.

In vivo measurements of muscle specific tension in adults and children

To better understand the effects of pubertal maturation on the contractile properties of skeletal muscle in vivo, the present study investigated whether there are any differences in the specific tension of the quadriceps muscle in 20 adults and 20 prepubertal children of both sexes. Specific tension was calculated as the ratio between the quadriceps tendon force and the sum of the physiological cross-sectional area (PCSA) multiplied by the cosine of the angle of pennation of each head within the quadriceps muscle. The maximal quadriceps tendon force was calculated from the knee extension maximal voluntary contraction (MVC) by accounting for EMG-based estimates of antagonist co-activation, incomplete quadriceps activation using the interpolation twitch technique and magnetic resonance imaging (MRI)-based measurements of the patellar tendon moment arm. The PCSA was calculated as the muscle volume, measured from MRI scans, divided by optimal fascicle length, measured from ultrasound images during MVC at the estimated angle of peak quadriceps muscle force. It was found that the quadriceps tendon force and PCSA of men (11.4 kN, 214 cm(2)) were significantly greater than those of the women (8.7 kN, 152 cm(2); P < 0.01). Both adult groups had greater values than the children (P < 0.01) but there were no differences between boys (5.2 kN, 99 cm(2)) and girls (6.1 kN, 102 cm(2)). Agonist activation was greater in men and women than in girls (P < 0.05), and antagonist activation was greater in men than in boys (P < 0.05). Moment arm length was greater in men than in boys or girls and greater in women than in boys (P < 0.05). The angle of pennation did not differ between the groups in any of the quadriceps heads. The specific tension was similar (P > 0.05) between groups: men, 55 +/- 11 N cm(-2); women, 57.3 +/- 13 N cm(-2); boys, 54 +/- 14 N cm(-2); and girls, 59.8 +/- 15 N cm(-2). These findings indicate that the increased muscle strength with maturation is not due to an increase in the specific tension of muscle; instead, it can be attributed to increases in muscle size, moment arm length and voluntary activation level.

Moment arms of the knee extensor mechanism in children and adults

In the present study we investigated whether there are differences in the patellar tendon moment arm (PTMA)-knee angle relationship between pre-pubertal children and adults, and whether the PTMA length scales to relevant anthropometric measurements in the two groups. Anthropometric characteristics and the PTMA length-joint angle relationships were determined in 20 adults and 20 pre-pubertal children of both genders. The anthropometric characteristics measured were height, body mass, knee circumference, medio-lateral knee breadth, anterior-posterior knee depth, leg length, femur length and tibia length. The PTMA was quantified from magnetic resonance images using the geometric centre of the femoral condyle method, at every 5 degrees between 55 degrees and 90 degrees of knee flexion (0 degrees is full extension). Adults had a significantly greater PTMA length at all joint angles (4.2 +/- 0.4 vs. 3.6 +/- 0.3 cm at 90 degrees ; P < 0.01), with the PTMA length decreasing from knee extension to knee flexion similarly in both adults and children. There were no significant and strong correlations between the PTMA and anthropometric measures in adults for any joint angle. In contrast, the PTMA correlated and scaled with anthropometric characteristics for the children (P < 0.05, r = 0.49-0.9) at all joint angles. The PTMA length in children was most accurately predicted at 85 degrees of flexion from the equation PTMA = -0.25 + 0.083 x tibia length + 0.02 x leg length (R(2) = 0.83). These findings indicate that the knee extensor mechanism in pre-pubertal children should not be considered to be a 'scaled-down' version of that in adults.

Influence of gait velocity on gastrocnemius muscle fascicle behaviour during stair negotiation

The gastrocnemius medialis (GM) muscle plays an important role in stair negotiation. The aim of the study was to investigate the influence of cadence on GM muscle fascicle behaviour during stair ascent and descent. Ten male subjects (young adults) walked up and down a four-step staircase (with forceplates embedded in the steps) at three velocities (63, 88 and 116 steps/min). GM muscle fascicle length was measured using ultrasonography. In addition, kinematic and kinetic data of the lower legs, and GM electromyography (EMG) were measured. For both ascent and descent, the amount of fascicular shortening, shortening velocity, knee moment, ground reaction force and EMG activity increased monotonically with gait velocity. The ankle moment increased up to 88 steps/min where it reached a plateau. The lack of increase in ankle moment coinciding with further shortening of the fascicles can be explained by an increased shortening of the GM musculotendon complex (MTC), as calculated from the knee and ankle angle changes, between 88 and 116 steps/min only. For descent, the relative instant of maximum shortening, which occurred during touch down, was delayed at higher gait velocities, even to the extent that this event shifted from the double support to the single support phase.

The proprioceptive and agonist roles of gastrocnemius, soleus and tibialis anterior muscles in maintaining human upright posture

Humans can stand using sensory information solely from the ankle muscles. Muscle length and tension in the calf muscles (gastrocnemius and soleus) are unlikely to signal postural sways on account of balance-related modulation in agonist activity. These facts pose two questions: (1) Which ankle muscles provide the proprioceptive information? (2) Which peripheral mechanism could modulate agonist activity? To address these issues, subjects were asked to stand normally on two force plates. Ultrasound and surface EMG were recorded from the calf and tibialis anterior (TA) muscles. For all nine subjects, changes in muscle length of TA were mainly (84 +/- 9% whole trial duration) orthodoxly correlated with bodily sway (centre of gravity, CoG), i.e. in accordance with passive ankle rotation. When orthodox, TA had the highest correlation with CoG (-0.66 +/- 0.07, deep compartment, P < 0.001). For five subjects, the superficial TA compartment showed counter-intuitive changes in muscle length with CoG, probably due to the flattening of the foot and proximal attachment geometry. Gastrocnemius and soleus were usually (duration 71 +/- 23 and 81 +/- 16%, respectively) active agonists (paradoxically correlated with CoG) but, for short periods of time, they could be orthodox and then presented a moderate correlation (0.38 +/- 0.16 and 0.28 +/- 0.09, respectively) with CoG. Considering the duration and extent to which muscle length is orthodox and correlated with CoG, TA may be a better source of proprioceptive information than the active agonists (soleus and gastrocnemius). Therefore, if a peripheral feedback mechanism modulates agonist activity then reciprocal inhibition acted by TA on the calf muscles is more likely to be effective than the autogenic pathway.

Mega-obese patients weighing more than 250 kg: a problematic group

BACKGROUND AND AIMS

The population with a BMI of 70kg/m2 or greater has been described and categorized as mega-obese. Mega-obese patients weighing more than 250kg constitute a special group of mega-obese patients that present more intra- and post-operative problems than other suprasuperobese.

MATERIAL AND METHODS

This is a retrospective analysis of 7 mega-obese patients weighing more than 250 kg, who underwent bariatric surgery. Patients' medical records were reviewed for length of stay, complications, co-morbidities, and weight loss.

RESULTS

Five patients were men and 2 were women. Co-morbidities included sleep apnoea syndrome (7 patients [100%]), venous ulcers (4 patients [57.1%]), post-thrombotic venous syndrome (3 patients [42.9%]), symptomatic cholelithiasis (3 patients [42.9%]), cellulites (3 patients [42.9%]), hypertension (4 patients [57.1%]), cardiac insufficiency (3 patients [42.9%]), and diabetes mellitus (1 patient [14.3%]). The length of stay averaged 15.3 days. Three patients presented short-term complications, 2 with long-term complications. Overall weight loss was 42.8% of excess body weight 6 months after surgery and 80.8% 2 years after surgery (when follow-up was completed).

CONCLUSIONS

Bariatric operations are safe and effective in the mega-obese population weighing more than 250 kg. Some minor modifications to the traditional techniques may be necessary, especially concerning equipment. Treatment of patients weighing more than 250 kg is problematic, presenting a relatively high percentage of short- and long-term complications, together with various intra-operative problems.

Influence of light handrail use on the biomechanics of stair negotiation in old age

The high incidence of falls in older adults during stair negotiation suggests that this task is physically challenging and potentially dangerous. The present study aimed to examine the influence of light handrail use on the biomechanics of stair negotiation in old age. Thirteen older adults ascended and descended a purpose-built staircase at their self-selected speed: (i) unaided and (ii) with light use of the handrails. Ground reaction forces (GRFs) were measured from force platforms mounted into each step and motion capture was used to collect kinematic data. Knee and ankle joint moments were calculated using the kinetic and kinematic data. The horizontal separation between the centre of mass (COM) and the centre of pressure (COP) was assessed in the sagittal and frontal planes. During stair ascent, handrail use caused a different strategy to be employed compared to unaided ascent with a redistribution of joint moments. Specifically, the ankle joint moment (of the trailing leg) was reduced with handrail use, which has previously been shown to approach its limits during unaided stair ascent, but the knee joint moment (of the leading leg) increased. Previous research has shown that a larger joint moment reserve is available at the knee during unaided stair ascent. During stair descent, the ankle joint moment increased with handrail use, this was associated, however, with a more effective control of balance as shown by a reduced COM-COP separation in the direction of progression compared to unaided descent. These results indicate that although the biomechanical mechanisms are different for stair ascent and descent, the safety of stair negotiation is improved for older adults with light use of the handrails.

Lower-limb biomechanics during stair descent: influence of step-height and body mass

The aim of the present study was to examine the biomechanics of the lower limb during stair descent and the effects of increasing demand in two ways: by increasing step-height and by increasing body mass. Ten male subjects walked down a four-step staircase, the height of which could be altered. The step-heights were: standard (17 cm), 50% decreased, 50% increased and 75%increased. At the standard height, subjects also walked down wearing a weighted jacket carrying 20% extra body mass. Lower limb kinematics and kinetics were determined using motion capture and ground reaction forces. Also measured were gastrocnemius medialis (GM) muscle electromyography and GM muscle fascicle length using ultrasonography. GM muscle fascicles actively shortened during the touch-down phase of stair descent in all conditions,while the muscle–tendon complex (MTC), as calculated from the knee and ankle joint kinematics, lengthened. The GM muscle fascicles shortened more when step-height was increased, which corresponded to the increase in ankle joint moment. Increased body mass did not alter the ankle or knee joint moment in the first contact phase of a step down; due to a change in strategy, the trailing leg, instead of the leading leg, supported the extra mass. Hence, the amount of GM muscle fascicle shortening, during the touch-down phase, also did not change with added body mass. Our results suggest that the increase in joint moments is related to the amount of fascicle shortening, which occurs whilst the MTC is lengthening, thereby stretching the elastic tendinous tissues.

The demands of stair descent relative to maximum capacities in elderly and young adults

In this study, we aimed to establish the joint moment and joint range of motion requirements of stair descent and the demands relative to maximal capacities in elderly and young adults. Participants descended a custom-built standard dimension four-step staircase, at their self-selected speed in a step-over manner. Kinetic data were acquired from force platforms embedded into each of the steps and into the floor at the base of the stairs. A motion analysis system was used to acquire kinematic data and joint moments were calculated using the kinematic and kinetic data. Maximum capacities (joint moment and joint range of motion) were assessed using a dynamometer. During stair descent the elderly generated lower absolute ankle joint moments than the young, which enabled them to operate at a similar relative proportion of their maximal capacity compared to young adults (75%). The knee joint moments during stair descent were similar between groups, but the elderly operated at a higher proportion of their maximal capacity (elderly: 42%; young: 30%). Ankle plantarflexion-dorsiflexion angle changes were similar between groups, which meant that the elderly operated at a higher proportion of their maximal assisted dorsiflexion angle. These results indicate that the elderly redistribute the joint moments in order to maintain the task demands within 'safe' limits.

Influence of step-height and body mass on gastrocnemius muscle fascicle behavior during stair ascent

To better understand the role of the ankle plantar flexor muscles in stair negotiation, we examined the effects of manipulation of kinematic and kinetic constraints on the behavior of the gastrocnemius medialis (GM) muscle during stair ascent. Ten subjects ascended a four-step staircase at four different step-heights (changing the kinematic constraints): standard (17 cm), 50% decreased, 50% increased and 75% increased. At the standard height, subjects also ascended the stairs wearing a weighted jacket, adding 20% of their body mass (changing the kinetic constraints). During stair ascent, kinematics and kinetics of the lower legs were determined using motion capture and ground reaction force measurements. The GM muscle fascicle length was measured during the task with ultrasonography. The amount of GM muscle fascicle shortening increased with step-height, coinciding with an increase in ankle joint moment. The increase in body mass resulted in an increased ankle joint moment, but the amount of GM muscle fascicle shortening during the lift-off phase did not increase, instead, the fascicles were shorter over the whole stride cycle. Increasing demands of stair ascent, by increasing step-height or body mass, requires higher joint moments. The increased ankle joint moment with increasing demands is, at least in part, produced by the increase in GM muscle fascicle shortening.

In vivo gastrocnemius muscle fascicle length in children with and without diplegic cerebral palsy

The effect of spastic cerebral palsy on in vivo gastrocnemius muscle fascicle length is not clear. Similarity of fascicle lengths in children with diplegia and typically developing children, but shortening of fascicle lengths in the paretic legs of children with hemiplegia compared with the non-paretic legs, are both reported. In the former case, comparisons were made between fascicle lengths normalized to leg length, whereas in the latter case, absolute fascicle lengths were compared. The inherent assumptions when normalizing fascicle length (measured via ultrasonography) were not validated, raising the possibility that inappropriate normalization contributed to the controversy. We used statistical methods to control the potential confounding effect of leg length on fascicle length, and tested the feasibility of the normalization method for a group of 18 children with diplegia (nine males, nine females; mean age 8y 7mo [SD 3y 11mo], range 2-15y; Gross Motor Function Classification System levels II and III) and 50 typically developing children (20 males, 30 females; mean age 9y 1mo [SD 2y 4mo], range 4-14y). Children with diplegia, as a group, had shorter absolute and normalized fascicle lengths (p<0.05) but we could not refute the appropriateness of the normalization method. Other methodological issues (such as sample characteristics) might have contributed to the apparent controversy between the studies.

Older adults employ alternative strategies to operate within their maximum capabilities when ascending stairs

Older people may operate much closer to their maximum capabilities than young adults when ascending stairs due to their lower maximum musculoskeletal capabilities. The purpose of this study was to establish the joint moment and range of motion demands of stair ascent relative to maximum capabilities in elderly and young adults. Fifteen elderly (mean age 75 years) and 17 young adult (mean age 25 years) participants ascended a purpose-built 4-step staircase with force platforms embedded into the steps and kinematic data was acquired using motion capture. Maximum musculoskeletal capabilities were assessed using a dynamometer. This study showed for the first time that stair ascent approaches the joint moment limits at the ankle in both young and older participants ( approximately 90%). One of the most important and novel findings of this study was that elderly people were only capable of meeting the high demands by adopting a number of alternative strategies not observed in young adults: (i) applying the joint moments differently than young adults across the knee and ankle, (ii) translocating energy from the knee to the ankle, thereby enhancing the ankle joint moment upon maximum demand and (iii) by enabling the plantarflexors to act over a more favourable portion of the moment-angle relation upon maximum ankle joint moment demand. The elderly displayed a more cautious strategy to optimize positional stability during stair ascent, by maintaining a smaller separation between the centre of mass and centre of pressure in the frontal plane. It seems that elderly people may meet the demands of unaided stair ascent by adopting a number of alternative strategies to compensate for their reduced musculoskeletal capabilities.

The impact of physical training on locomotor function in older people

Locomotor function declines in old age. Based on 55 studies, this review appraises current evidence on the impact of physical training interventions on locomotor function in older people. Overall, the literature indicates that physical training can have a beneficial impact on locomotor function in older people. This also holds true in various sub-populations including those who are very old, those who have functional limitations and those with chronic health problems. Improvements in locomotor function can be seen within 4-6 weeks of physical training, although the potential that improvements may appear earlier has not been investigated. Recent studies provide evidence of a dose-response relationship between intensity of strength training and improvement in locomotor function in older people. However, whether such a relationship exists for other training modes has not yet been investigated. Based on current evidence, the optimal training modes or combination of training modes (strength, aerobic, balance, coordination, etc.) and the optimal frequency of training for improvement in locomotor function are unclear.

Centre of mass motion during stair negotiation in young and older men

The aim of this study was to compare centre of mass (COM) motion and its separation from centre of pressure (COP) as 13 young men (aged 23-36 years) and 15 healthy, community dwelling older men (aged 73-84 years) ascended and descended a three step staircase at a controlled cadence of approximately 90 steps/min. Centre of mass was obtained from whole body motion analysis, and simultaneously, COP was obtained using force plates built into the steps. The following variables were investigated: medio-lateral COM range of motion; peak antero-posterior and medio-lateral COM-COP separation; and peak antero-posterior, medio-lateral, and vertical COM velocities. No significant differences in these variables between young men and older men were present during ascent or descent. It was concluded that frontal plane dynamic stability during stair negotiation is well maintained in healthy older men, and that healthy older men do not exhibit an altered strategy in traversing the COM in the plane of progression during stair negotiation.

Gastrocnemius muscle fascicle behavior during stair negotiation in humans

The aim of the present study was to establish the behavior of human medial gastrocnemius (GM) muscle fascicles during stair negotiation. Ten healthy male subjects performed normal stair ascent and descent at their own comfortable speed on a standard-dimension four-step staircase with embedded force platforms in each step. Kinematic, kinetic, and electromyographic data of the lower limbs were collected. Real-time ultrasound scanning was used to determine GM muscle fascicle length changes. Musculotendon complex (MTC) length changes were estimated from ankle and knee joint kinematics. The GM muscle was mainly active during the push-off phase in stair ascent, and the muscle fascicles contracted nearly isometrically. The GM muscle was mainly active during the touch-down phase of stair descent where the MTC was lengthened; however, the GM muscle fascicles shortened by ∼7 mm. These findings show that the behavior and function of GM muscle fascicles in stair negotiation is different from that expected on the basis of length changes of the MTC as derived from joint kinematics.

In vivo changes in the human patellar tendon moment arm length with different modes and intensities of muscle contraction

The purpose of this study was to examine the effect of different muscle contraction modes and intensities on patellar tendon moment arm length (d(PT)). Five men performed isokinetic concentric, eccentric and passive knee extensions at an angular velocity of 60 deg/s and six men performed gradually increasing to maximum effort isometric muscle contractions at 90( composite function) and 20( composite function) of knee flexion. During the tests, lateral X-ray fluoroscopy imaging was used to scan the knee joint. The d(PT) differences between the passive state and the isokinetic concentric and extension were quantified at 15( composite function) intervals of knee joint flexion angle. Furthermore, the changes of the d(PT) as a function of the isometric muscle contraction intensities were determined during the isometric knee extension at 90( composite function) and 20( composite function) of knee joint flexion. Muscle contraction-induced changes in knee joint flexion angle during the isometric muscle contraction were also taken into account for the d(PT) measurements. During the two isometric knee extensions, d(PT) increased from rest to maximum voluntary muscle contraction (MVC) by 14-15%. However, when changes in knee joint flexion angle induced by the muscle contraction were taken into account, d(PT) during MVC increased by 6-26% compared with rest. Moreover, d(PT) increased during concentric and eccentric knee extension by 3-15%, depending on knee flexion angle, compared with passive knee extension. These findings have important implications for estimating musculoskeletal loads using modelling under static and dynamic conditions.

Kinematics of stair descent in young and older adults and the impact of exercise training

Stair descent is a challenging task in old age. This study firstly investigated lower extremity kinematics during stair descent in young (YOU) and healthy, community dwelling older adults (OLD). Secondly, the impact of an exercise training intervention on age-related differences in stair descent was assessed. At baseline, a motion analysis system was used to determine spatio-temporal gait variables and lower extremity kinematics as YOU (n=23, age=27+/-3 years) and OLD (n=34, age=73+/-4 years) descended a three step staircase. The older adults were then divided into training (TRA) and control (CON) groups. For 12 months, TRA performed resistance, aerobic, balance, and flexibility exercises under supervision in a class environment (twice per week) and unsupervised at home (once per week). CON carried on with normal daily activities. Following the intervention, baseline measurements were repeated in TRA and CON. At baseline, total descent, stride cycle, and single support times were longer in OLD than in YOU. In addition, sagittal plane knee motion was lower in OLD whilst frontal and transverse plane pelvis and hip motion were higher in OLD. Exercise training did not reduce the age-related differences observed. In conclusion healthy older adults perform stair descent at a slower speed and with greater motion outside the plane of progression than young adults. We found no evidence that these differences are reduced by generic exercise training, at least in non-frail older adults.

Human patellar tendon moment arm length: measurement considerations and clinical implications for joint loading assessment

Detailed understanding of the knee joint loading requires the calculation of muscle and joint forces in different conditions. In these applications the patellar tendon moment arm length is essential for the accurate estimation of the tibiofemoral joint loading. In this article, different methods that have been used to determine the patellar tendon moment arm length under in vivo and in vitro conditions are reviewed. The limitations and advantages associated with each of the methods are evaluated together with their applications in the different loading conditions that the musculoskeletal system is subjected to. The three main measurement methods that this review considers are the geometric method, the tendon excursion method and the direct load method. A comparison of relevant quantitative results is presented to asses the impact of the errors of each method on the quantification of the patellar tendon moment arm and the implications for joint loading assessment in clinical applications.

Can the patellar tendon moment arm be predicted from anthropometric measurements?

The purpose of this study was to examine the relations between patellar tendon moment arm length and several relevant anthropometric characteristics of 22 healthy men. The patellar tendon moment arm length was measured using magnetic resonance imaging with two different methods: (1) measurement of patellar tendon moment arm length (d(PT)) with respect to the tibiofemoral contact point (d(PTCP)) and (2) measurement of d(PT) with respect to the intersection point of the anterior and posterior cruciate ligament (d(PTIP)). Pearson correlation coefficients and a stepwise linear regression analysis were used to examine the relationships between the d(PT) and anthropometric measurements taken. Furthermore, a Student's t-test was used to determine differences between the d(PTCP) and d(PTIP) values. Only knee circumference was a significant d(PTCP) predictor (P < 0.05) but with a very low R2 (0.139). None of the anthropometric parameters examined was found to be a significant d(PTIP) predictor. The correlation coefficients ranged from -0.04 to 0.42. The d(PTIP) values were significantly higher (by 0.84-1.89 cm) than the d(PTCP) values (P < 0.05). These results are in disagreement with previous in vitro findings that d(PT) variance may be explained by knee joint size differences. Hence, existing imaging-based methodologies remain necessary for accurate quantification of the patellar tendon moment arm.