Medial Gastrocnemius Tendon Research Articles

The Relationship Between Medial Gastrocnemius Lengthening Properties and Stretch Reflexes in Cerebral Palsy.

Stretch reflex hyperactivity in the gastrocnemius of children with spastic cerebral palsy (CP) is commonly evaluated by passively rotating the ankle joint into dorsiflexion at different velocities, such as applied in conventional clinical spasticity assessments. However, surface electromyography (sEMG) collected from the medial gastrocnemius (MG) during such examination reveals unexplained heterogeneity in muscle activation between patients. Recent literature also highlights altered muscle tensile behavior in children with spastic CP. We aimed to document MG muscle and tendon lengthening during passive ankle motion at slow and fast velocity and explore its interdependence with the elicited hyperactive stretch reflex. The ankle of 15 children with CP (11 ± 3 years, GMFCS 9I 6II, 8 bilateral, 7 unilateral) and 16 typically developing children (TDC) was passively rotated over its full range of motion at slow and fast velocity. Ultrasound, synchronized with motion-analysis, was used to track the movement of the MG muscle-tendon junction and extract the relative lengthening of muscle and tendon during joint rotation. Simultaneously, MG sEMG was measured. Outcome parameters included the angular and muscle lengthening velocities 30 ms before EMG onset and the gain in root mean square EMG during stretch, as a measure of stretch reflex activity. Compared to slow rotation, the muscle lengthened less and stretch reflex activity was higher during fast rotation. These velocity-induced changes were more marked in CP compared to TDC. In the CP group, muscle-lengthening velocity had higher correlation coefficients with stretch reflex hyperactivity than joint angular velocity. Muscles with greater relative muscle lengthening during slow rotation had earlier and stronger stretch reflexes during fast rotation. These initial results suggest that ankle angular velocity is not representative of MG muscle lengthening velocity and is less related to stretch reflex hyperactivity than MG muscle lengthening. In addition, muscles that lengthened more during slow joint rotation were more likely to show a velocity-dependent stretch reflex. This interdependence of muscle lengthening and stretch reflexes may be important to consider when administering treatment. However, muscle and tendon lengthening properties alone could not fully explain the variability in stretch reflexes, indicating that other factors should also be investigated.

Matching Participants for Triceps Surae Muscle Strength and Tendon Stiffness Does Not Eliminate Age-Related Differences in Mechanical Power Output During Jumping.

Reductions in muscular power output and performance during multi-joint motor tasks with aging have often been associated with muscle weakness. This study aimed to examine if matching younger and middle-aged adults for triceps surae (TS) muscle strength and tendon stiffness eliminates age-related differences in muscular power production during drop jump. The maximal ankle plantar flexion moment and gastrocnemius medialis tendon stiffness of 29 middle-aged (40–67 years) and 26 younger (18–30 years) healthy physically active male adults were assessed during isometric voluntary ankle plantar flexion contractions using simultaneous dynamometry and ultrasonography. The elongation of the tendon during the loading phase was assessed by digitizing the myotendinous junction of the gastrocnemius medialis muscle. Eight younger (23 ± 3 years) and eight middle-aged (54 ± 7 years) adults from the larger subject pool were matched for TS muscle strength and tendon stiffness (plantar flexion moment young: 3.1 ± 0.4 Nm/kg; middle-aged: 3.2 ± 0.5 Nm/kg; tendon stiffness: 553 ± 97 vs. 572 ± 100 N/mm) and then performed series of drop jumps from different box heights (13, 23, 33, and 39 cm) onto a force plate (sampling frequency 1000 Hz). The matched young and middle-aged adults showed similar drop jump heights for all conditions (from lowest to highest box height: 18.0 ± 3.7 vs. 19.7 ± 4.8 cm; 22.6 ± 4.2 vs. 22.9 ± 4.9 cm; 24.8 ± 3.8 vs. 23.5 ± 4.9 cm; 25.2 ± 6.2 vs. 22.7 ± 5.0 cm). However, middle-aged adults showed longer ground contact times (on average 36%), lower vertical ground reaction forces (36%) and hence lower average mechanical power (from lowest to highest box height: 2266 ± 563 vs. 1498 ± 545 W; 3563 ± 774 vs. 2222 ± 320 W; 4360 ± 658 vs. 2475 ± 528 W; 5008 ± 919 vs. 3034 ± 435 W) independent of box height. Further, leg stiffness was lower (48%) in middle-aged compared to younger adults for all jumping conditions and we found significant correlations between average mechanical power and leg stiffness (0.70 ≤ r ≤ 0.83; p < 0.01). Thus, while jumping performance appears to be unaffected when leg extensor muscle strength and tendon stiffness are maintained, the reduced muscular power output during lower limb multi-joint tasks seen with aging may be due to age-related changes in motor task execution strategy rather than due to muscle weakness.

A polygon-shaped complex appearance of medial patellofemoral ligament with dynamic functional insertion based on an outside-in and inside-out dissection technique.

To describe the unclarified characteristics of medial patellofemoral ligament and its relation to neighboring structures. Sixteen fresh-frozen human knees were dissected in using outside-in and inside-out combined technique. The patellar side attachment was observed from the inside view and femoral side from outside view. The medial patellofemoral ligament was described a complex and multiconnected structure. The femoral side included the upper and lower portion, of which the upper portion attached on the femur with mean width 7.5±1.1 mm and its superficial fibers extended to the adductor magnus tendon and the medial gastrocnemius tendon, and of which the lower portion appeared a right-triangle connected to the MCL without bony attachment. From inside view, the patellar attachment consisted of the bony and non-bony parts. The width of bony attachment was measured mean 16.3±3.8mm, and the non-bony attachment was found attached on the vastus intermedius tendon with mean width 21.7±4.8mm. The average thickness was 0.4±0.1mm and the length were inside assessed mean 67.9±6.1mm. The medial patellofemoral ligament which dissected a complicated structure with bony and non-bony attachment and multi-connected to neighboring structures on both patella and femur side appears as a polygon-shaped complex structure.

Between-day reliability of MyotonPRO for the non-invasive measurement of muscle material properties in the lower extremities of patients with a chronic spinal cord injury

Measuring the muscle properties of patients with spinal cord injuries (SCIs) is important to better understand their biomechanical features. In this study, we sought to evaluate the between-day reliability of MyotonPRO, a handheld device that can measure muscle mechanical properties, and assess whether it is reliable to measure muscle properties over time in patients with SCI. Thirteen men with complete SCIs (age 53.9 ± 6.3 years, height 171.0 ± 5.2 cm, weight 66.1 ± 5.8 kg), and injury levels ranging from L1 to T12, were enrolled. Oscillation frequency; logarithmic decrement; dynamic stiffness; mechanical stress relaxation time; and creep of the biceps femoris, medial and lateral gastrocnemius, rectus femoris, tibialis anterior, and Achilles tendon were measured on consecutive days using MyotonPRO. The intraclass coefficient for most muscles and the Achilles tendon ranged from 0.53 to 0.99 for all parameters. The percentage standard error of the measurement for many parameters in most muscles and the Achilles tendon was less than 10%. Bland-Altman analysis showed a high agreement for all mechanical properties. No significant differences were observed in any muscle or Achilles tendon properties between days (all p > 0.05). These results indicate that the MyotonPRO is reliable for between-day measurements of the mechanical properties of lower limb muscles and Achilles tendon in patients with SCI.

Medial gastrocnemius and soleus muscle-tendon unit, fascicle, and tendon interaction during walking in children with cerebral palsy.

This study investigates the invivo function of the medial gastrocnemius and soleus muscle-tendon units (MTU), fascicles, and tendons during walking in children with cerebral palsy (CP) and an equinus gait pattern. Fourteen children with CP (9 males, 5 females; mean age 10y 6mo, standard deviation [SD] 2y 11mo; GMFCS level I=8, II=6), and 10 typically developing (6 males, 4females; mean age 10y, SD 2y 1mo) undertook full body 3D gait analysis and simultaneous B-mode ultrasound images of the medial gastrocnemius and soleus fascicles during level walking. Fascicle lengths were analysed using a semi-automated tracking algorithm and MTUs using OpenSim. Statistical parametric mapping (two-sample t-test) was used to compare differences between groups (p<0.05). In the CP group medial gastrocnemius fascicles lengthened during mid-stance gait and remained longer into late-stance compared to the typically developing group (p<0.001). CP medial gastrocnemius fascicles shortened less during stance (1.16mm [SD 1.47mm]) compared to the typically developing group (4.48mm [SD 1.94mm], p<0.001). In the CP group the medial gastrocnemius and soleus MTU and tendon were longer during early- and mid-stance (p<0.001). Ankle power during push-off (p=0.015) and positive work (p<0.002) and net work (p<0.001) were significantly lower in the CP group. Eccentric action of the CP medial gastrocnemius muscle fascicles during mid-stance walking is consistent with reduced volume and neuromuscular control of impaired muscle. Reduced ankle push-off power and positive work in the children with CP may be attributed to reduced active medial gastrocnemius fascicle shortening. These findings suggest a reliance on passive force generation for forward propulsion during equinus gait.

Use of a Lucas–Kanade-Based Template Tracking Algorithm to Examine In Vivo Tendon Excursion during Voluntary Contraction Using Ultrasonography

Ultrasound imaging can be used to study tendon movement during muscle contraction to estimate the tendon force–length relationship in vivo. Traditionally, such tendon displacement measurements are made manually (time consuming and subjective). Here we evaluated a Lucas–Kanade-based tracking algorithm with an optic flow extension that accounts for tendon movement characteristics between consecutive frames of an ultrasound image sequence. Eleven subjects performed 12 voluntary isometric plantar flexion contractions on a dynamometer. Simultaneously, the gastrocnemius medialis tendon was visualized via ultrasonography. Tendon displacement was estimated manually and by using two different automatic tracking algorithms. Maximal tendon elongation (manual: 17.9 ± 0.3 mm, automatic: 17.0 ± 0.3 mm) and tendon stiffness (209 ± 4 N/mm, 218 ± 5 N/mm) generated by the developed algorithm correlated with those obtained with the manual method (0.87 ≤ R ≤ 0.91), with no differences between methods. Our results suggest that optical flow methods can potentially be used for automatic estimation of tendon movement during contraction in ultrasound images, which is further improved by adding a penalty function.

The effect of cadence on the muscle-tendon mechanics of the gastrocnemius muscle during walking.

Humans naturally select a cadence that minimizes metabolic cost at a constant walking velocity. The aim of this study was to examine the effects of cadence on the medial gastrocnemius (MG) muscle and tendon interaction, and examine how this might influence lower limb energetics. We hypothesized that cadences higher than preferred would increase MG fascicle shortening velocity because of the reduced stride time. Furthermore, we hypothesized that cadences lower than preferred would require greater MG fascicle shortening to achieve increased muscle work requirements. We measured lower limb kinematics and kinetics, surface electromyography of the triceps surae and MG fascicle length, via ultrasonography, during walking at a constant velocity at the participants' preferred cadence and offsets of ±10%, ±20%, and ±30%. There was a significant increase in MG fascicle shortening with decreased cadence. However, there was no increase in the MG fascicle shortening velocity at cadences higher than preferred. Cumulative MG muscle activation per minute was significantly increased at higher cadences. We conclude that low cadence walking requires more MG shortening work, while MG muscle and tendon function changes little for each stride at higher cadences, driving up cumulative activation costs due to the increase in steps per minute.

Arthroscopic patterns of the poster-medial aspect of the knee joint: classification of the gastrocnemiussemimembranosus gateway and its relationship with Baker�s cyst

The gastrocnemius-semimembranosus bursa may communicate with the knee joint. The arthroscopic anatomy of the posteromedial aspect varies depending on the angle of the oblique popliteal ligament, the level at which it crosses the medial gastrocnemius tendon, and its relationship with the capsular joint and synovia. The aim of this paper is to identify possible patterns, and to evaluate their characteristics and their relationship with Baker's cyst. data archived from 185 consecutive arthroscopies were evaluated; an anatomic description and classification was carried out; the percentages of association with BC and the associated pathologies were reported. The different anatomies were classified into six groups based on the relationship above the medial gastrocnemius tendon, the capsular joint and synovia. The prevalence of Baker's cyst was 28.3%. The main associated intra-articular pathological condition was the contemporary presence of a meniscal tear and chondropathy. Exploration of the posterior aspect of the knee must be performed routinely. Knowing the possible anatomy patterns of the posteromedial arthroscopic aspect of the knee joint could help to identify the cyst and its gateway, thus facilitating its treatment. III.

Age-specific neuromuscular interaction during elderly habitual running.

It has been reported that advancing age causes tendons to become more compliant and fascicles length shorter. This could then lead to enhancement of movement efficiency provided that the elderly adults can activate their muscles in the same way as the younger adults (YOUNG) during dynamic movements. This study was designed to examine the age-specific behaviour of the medial gastrocnemius (MG) fascicles and tendinous tissues together with lower-leg muscle activities when the well-trained elderly runners ran on the treadmill at preferred speeds. The well-trained 11 elderly subjects (ELD) who have running experiences and 11 YOUNG were recruited as subjects. While ELD were running on the treadmill at their preferred speed, the lengths of the MG fascicles and tendinous tissues (Lfa and LTT respectively) were measured by ultrasonography together with kinematics and lower-leg muscle activities. Although the behaviour of the MG muscle-tendon unit did not show any significant differences between both groups during the contact, our results showed significant differences in fascicle-tendinous tissue behaviour as well as muscle activities. The LTT during the entire contact phase was greater in ELD than in YOUNG (P<0.001). Co-activation of lower-leg muscles from pre-activation to braking phases was higher in ELD than in YOUNG (P<0.01). The changes of the Lfa during contact were less, and the LTT shortening was greater in ELD than in YOUNG (P<0.001). These results imply that ELD cannot activate their muscles similar to YOUNG during running, and those different activities may modify the Lfa to utilize the tendon elasticity effectively.

Effects of ankle–foot braces on medial gastrocnemius morphometrics and gait in children with cerebral palsy

PurposeIn children with cerebral palsy (CP), braces are used to counteract progressive joint and muscle contracture and improve function. We examined the effects of positional ankle–foot braces on contracture of the medial gastrocnemius (MG) and gait in children with CP while referencing to typically developing children.MethodsSeventeen independently ambulant children with CP and calf muscle contracture (age 10.4 ± 3.0y) and 17 untreated typically developing peers (age 9.5 ± 2.6y) participated. Children with CP were analysed before and 16 ± 4 weeks after ankle–foot bracing. MG muscle belly length and thickness, tendon and fascicle length, as well as their extensibility were captured by 2D ultrasound and 3D motion capturing during passive, manually applied stretches. In addition, 3D gait analysis was conducted.ResultsPrior to bracing, the MG muscle–tendon unit in children with CP was 22 % less extensible. At matched amounts of muscle–tendon unit stretch, the muscle belly and fascicles in CP were 7 % and 14 % shorter while the tendon was 11 % longer. Spastic fascicles displayed 32 % less extensibility than controls. Brace wear increased passive dorsiflexion primarily with the knees flexed. During gait, children walked faster and foot lift in swing improved. MG muscle belly and tendon length showed little change, but fascicles further shortened (−11 %) and muscle thickness (−8 %) decreased.ConclusionsUse of ankle–foot braces improves function but may lead to a loss of sarcomeres in series, which could explain the shortened fascicles. To potentially induce gastrocnemius muscle growth, braces may also need to extend the knee or complementary training may be necessary to offset the immobilizing effects of braces.

The relationship between lower-body stiffness and dynamic performance

Greater levels of lower-body stiffness have been associated with improved outcomes for a number of physical performance variables involving rapid stretch-shorten cycles. The aim of this study was to investigate the relationship between several measures of lower-body stiffness and physical performance variables typically evident during team sports in female athletes. Eighteen female athletes were assessed for quasi-static stiffness (myometry) for several isolated muscles in lying and standing positions. The muscles included the medial gastrocnemius (MedGast), lateral gastrocnemius, soleus, and Achilles tendon. Dynamic stiffness during unilateral hopping was also assessed. Participants were separated into relatively stiff and compliant groups for each variable. A number of significant differences in performance were evident between stiff and compliant subjects. When considering the quasi-static stiffness of the MedGast in lying and standing positions, relatively stiff participants recorded significantly superior results during agility, bounding, sprinting, and jumping activities. Stiffness as assessed by hopping did not discriminate between performance ability in any test. Relationships highlighted by MedGast results were supported by further significant differences in eccentric utilisation ratio and drop jump results between stiff and compliant groups for the lateral gastrocnemius and soleus in lying and standing positions. Higher levels of lower-body stiffness appear to be advantageous for females when performing rapid and (or) repeated stretch-shorten cycle movements, including sprinting, bounding, and jumping. Further, the stiffness of the MedGast is of particular importance during the performance of these activities. It is important for practitioners working with athletes in sports that rely upon these activities for success to consider stiffness assessment and modification.

Muscle–tendon interaction and EMG profiles of world class endurance runners during hopping

The present study examined the muscle-tendon interaction of ten international level Kenyan runners. Ultrasonography and kinematics were applied together with EMG recordings of lower limb muscles during repetitive hopping performed at maximal level. The ten Kenyans had longer gastro Achilles tendon at rest (p < 0.01) as compared with ten control subjects matched in height. Conversely, the stretching and shortening amplitudes of the tendinous tissues of the medial gastrocnemius (MG) muscle were significantly smaller in the Kenyans than in controls during the contact phase of hopping. This applied also to the fascicle length changes, which were smaller and more homogeneous among Kenyans. These limited musculo-tendinous changes resulted in higher maximal hopping height and in larger power despite their reduced body weight. The associated finding of a greater shortening to stretching ratio of the MG tendinous tissues during contact could imply that the Kenyan MG muscle-tendon unit is optimized to favor efficient storage and recoil of elastic energy, while operating at optimal muscle fascicle working range (plateau region).

Gastrocnemius tendon length and strain are different when assessed using straight or curved tendon model

The present study investigated the effects of tendon curvature on measurements of tendon length using 3D-kinematic analysis. Curved and straight tendon models were employed for assessing medial gastrocnemius tendon length and strain during hopping (N = 8). Tendon curvature was identified using small reflective markers placed on the skin surface along the length of the tendon and a sum of vectors between the markers from the calcaneous up to the marker at the origin of tendon was calculated. The straight tendon was defined as a length of vector from the calcaneous to the marker at the origin of tendon. The curved tendon method yielded 5.0 ± 1.3 mm longer tendon (p < 0.001) than the straight tendon model. Tendon elongation was 2.1 ± 1.6 mm and peak strain 1.3 ± 0.7% smaller in curved than in straight tendon model (p < 0.01). The results suggest that the commonly used straight tendon model underestimate slightly but significantly the true tendon length but overestimate the strain and elongation.

Effect Of Tendon Stiffness And Leg Stiffness On Running Economy In Well-trained Middle Distance Runners

PURPOSE: Previous research suggests that a stiff 'leg spring' during running can provide significant energy savings from the elastic properties in the leg‘s soft tissues. Knowing that the absorption and recovery of elastic energy in muscle-tendon units is important in determining the energy cost of running, researchers have used the leg stiffness measured during the ground contact phase in running as a surrogate for muscle-tendon stiffness. However, no research has examined both the leg spring stiffness and the stiffness of the major tendons simultaneously. The aim of the present study was to examine how leg stiffness and the mechanical properties of the primary ankle and knee tendons influence running economy. METHODS: Eleven well-trained male middle distance runners volunteered for the study. Medial gastrocnemius (MG) and vastus lateralis (VL) tendon force-elongation properties were measured during an isometric maximal voluntary contraction. Tendon forces were determined from joint moments measured by isokinetic dynamometry, corrected for agonist-antagonist co-contraction and joint rotation. Tendon elongation was measured using B-mode 2-D ultrasonography. Eccentric leg stiffness was measured during over-ground running using a previously published kinetic model. Total leg stiffness of the entire ground contact phase was derived from kinetic and kinematic measures. Running economy was measured using a standardised incremental treadmill protocol. RESULTS: Analysis revealed no correlation with MG or VL tendon stiffness and either eccentric (r = -0.03 and r = -0.07, respectively) or total leg stiffness (r = -0.06 and r = 0.16, respectively). Leg stiffness was not correlated with running economy; however, MG tendon stiffness and peak ankle joint moment were significantly correlated with economy (r = -0.66 and r = -0.68, respectively). CONCLUSIONS: Leg stiffness does not appear to be a surrogate for tendon stiffness and is not predictive of running economy in well-trained runners. Leg stiffness might be influenced by changes in leg mechanics or muscular co-contraction. Interestingly, Achilles tendon stiffness tends to be greater in more economical runners. Faster tendon recoil, indicative of stiffer tendons, could benefit power generation at the ankle joint during high speed running.

Menstrual cycle variations in oestradiol and progesterone have no impact on in vivo medial gastrocnemius tendon mechanical properties

Background Tendon tissue contains oestrogen receptors and is therefore likely to be responsive to female sex hormones. Here we examine any effect of levels of female sex hormones associated with the menstrual cycle phase on corresponding tendon mechanical properties. Methods Fifteen healthy females aged 23 (SEM 1.0 years) underwent three assessments of medial gastrocnemius tendon mechanical properties. Assessments were carried out once during days 1–4, 12–14 and 20–23 (with day 1 being the first day of menstruation). Venous blood samples were taken on the same days as tendon properties assessments to quantify serum levels of oestradiol and progesterone. Findings There was no significant difference in the stiffness of the medial gastrocnemius tendon over the course of the menstrual cycle (days 1–4, 65.08 (SEM 5.16 Nm m −1), days 12–14, 62.73 (SEM 5.82 Nm m −1), days 20–23, 66.74 (SEM 7.14 Nm m −1)). There were also no significant differences in tendon length and cross-sectional area which led to no significant differences in Young’s modulus values. No correlations were found between serum levels of oestradiol and/or progesterone and tendon stiffness and/or Young’s modulus. Interpretation Acute fluctuations in female sex hormones have no significant effect on medial gastrocnemius tendon mechanical properties. In a context where studies are often limited to selecting only oral contraceptive-users as participants in order to minimise potential noise related to the anticipated effects of menstrual cycle hormones on physical performance, our findings provide the basis for enabling the pooling of female tendon data, regardless of the phase of the menstrual cycle of individual participant.

Effect of acute tensile loading on gender‐specific tendon structural and mechanical properties

Stretching is commonly used prior to exercise, as it is thought to reduce the risk of injury, and it is also used in the preconditioning of tendon grafts. As tendon properties have been shown to be different between genders, it is proposed that stretching will differentially affect the structure. Here we examine the effect of acute stretch on the mechanical properties of both male and female medial gastrocnemius tendon. Female [20 years +/- 1 (SEM), n = 17] and male (22 years +/- 1, n = 18) subjects underwent a 5-min passive dorsiflexion stretch. Prior to and post stretch medial gastrocnemius tendon stiffness (K), length (l) and cross-sectional area (csa) were measured using ultrasonography and dynamometry. Stiffness and Young's modulus (epsilon) were significantly reduced with stretch for both genders (p < 0.05). Females showed significantly (p < 0.05) greater pre- to poststretch decreases in K (22.4 vs. 8.8%) and epsilon (20.5 vs. 8.4%) in comparison to males. The present results show that stretching acutely reduces stiffness of the medial gastrocnemius tendon in females and males, with females showing significantly greater change. The observed disparity between genders may be due in part to variations in tendon moment arm and intrinsic differences in tendon composition. These differential changes in tendon mechanical properties have functional, motor control, and injury risk implications, as well as possible implications for preconditioning of tendon grafts.

The Anatomy of the Medial Part of the Knee

While the anatomy of the medial part of the knee has been described qualitatively, quantitative descriptions of the attachment sites of the main medial knee structures have not been reported. The purpose of the present study was to verify the qualitative anatomy of medial knee structures and to perform a quantitative evaluation of their anatomic attachment sites as well as their relationships to pertinent osseous landmarks. Dissections were performed and measurements were made for eight nonpaired fresh-frozen cadaveric knees with use of an electromagnetic three-dimensional tracking sensor system. In addition to the medial epicondyle and the adductor tubercle, a third osseous prominence, the gastrocnemius tubercle, which corresponded to the attachment site of the medial gastrocnemius tendon, was identified. The average length of the superficial medial (tibial) collateral ligament was 94.8 mm. The superficial medial collateral ligament femoral attachment was 3.2 mm proximal and 4.8 mm posterior to the medial epicondyle. The superficial medial collateral ligament had two separate attachments on the tibia. The distal attachment of the superficial medial collateral ligament on the tibia was 61.2 mm distal to the knee joint. The deep medial collateral ligament consisted of meniscofemoral and meniscotibial portions. The posterior oblique ligament femoral attachment was 7.7 mm distal and 6.4 mm posterior to the adductor tubercle and 1.4 mm distal and 2.9 mm anterior to the gastrocnemius tubercle. The medial patellofemoral ligament attachment on the femur was 1.9 mm anterior and 3.8 mm distal to the adductor tubercle. The medial knee ligament structures have a consistent attachment pattern.

The Anatomy of the Medial Part of the Knee

Background: While the anatomy of the medial part of the knee has been described qualitatively, quantitative descriptions of the attachment sites of the main medial knee structures have not been reported. The purpose of the present study was to verify the qualitative anatomy of medial knee structures and to perform a quantitative evaluation of their anatomic attachment sites as well as their relationships to pertinent osseous landmarks. Methods: Dissections were performed and measurements were made for eight nonpaired fresh-frozen cadaveric knees with use of an electromagnetic three-dimensional tracking sensor system. Results: In addition to the medial epicondyle and the adductor tubercle, a third osseous prominence, the gastrocnemius tubercle, which corresponded to the attachment site of the medial gastrocnemius tendon, was identified. The average length of the superficial medial (tibial) collateral ligament was 94.8 mm. The superficial medial collateral ligament femoral attachment was 3.2 mm proximal and 4.8 mm posterior to the medial epicondyle. The superficial medial collateral ligament had two separate attachments on the tibia. The distal attachment of the superficial medial collateral ligament on the tibia was 61.2 mm distal to the knee joint. The deep medial collateral ligament consisted of meniscofemoral and meniscotibial portions. The posterior oblique ligament femoral attachment was 7.7 mm distal and 6.4 mm posterior to the adductor tubercle and 1.4 mm distal and 2.9 mm anterior to the gastrocnemius tubercle. The medial patellofemoral ligament attachment on the femur was 1.9 mm anterior and 3.8 mm distal to the adductor tubercle. Conclusions: The medial knee ligament structures have a consistent attachment pattern. Clinical Relevance: Identification of the gastrocnemius tubercle and the quantitative relationships presented here will be useful in the study of anatomic repairs and reconstructions of complex ligamentous injuries that involve the medial knee structures.

PLYOMETRIC VS.ISOMETRIC TRAINING INFLUENCES ON TENDON PROPERTIES AND MUSCLE OUTPUT

The purpose of this study was to concurrently determine the effect that plyometric and isometric training has on tendon stiffness (K) and muscle output characteristics to compare any subsequent changes. Thirteen men trained the lower limbs either plyometrically or isometrically 2–3 times a week for a 6-week period. Medial gastrocnemius tendon stiffness was measured in vivo using ultrasonography during ramped isometric contractions before and after training. Mechanical output variables were measured using a force plate during concentric and isometric efforts. Significant (p < 0.05) training-induced increases in tendon K were seen for the plyometric (29.4%; 49.0 < 10.8 to 63.4 < 9.2 N·mm-1) and isometric groups (61.6%; 43.9 < 2.5 to 71.0 < 7.4 N·mm-1). Statistically similar increases in rate of force development and jump height were also seen for both training groups, with increases of 18.9 and 58.6% for the plyometric group and 16.7 and 64.3% for the isometric group, respectively. Jump height was found to be significantly correlated with tendon stiffness, such that stiffness could explain 21% of the variance in jump height. Plyometric training has been shown to place large stresses on the body, which can lead to a potential for injury, whereas explosive isometric training has been shown here to provide similar benefits to that of plyometric training with respect to the measured variables, but with reduced impact forces, and would therefore provide a useful adjunct for athletic training programs within a 6-week time frame.

Expression of collagen and related growth factors in rat tendon and skeletal muscle in response to specific contraction types

Acute exercise induces collagen synthesis in both tendon and muscle, indicating an adaptive response in the connective tissue of the muscle-tendon unit. However, the mechanisms of this adaptation, potentially involving collagen-inducing growth factors (such as transforming growth factor-beta-1 (TGF-beta-1)), as well as enzymes related to collagen processing, are not clear. Furthermore, possible differential effects of specific contraction types on collagen regulation have not been investigated. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric or isometric training (n = 7-9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve. RNA was extracted from medial gastrocnemius and Achilles tendon tissue 24 h after the last training bout, and mRNA levels for collagens I and III, TGF-beta-1, connective tissue growth factor (CTGF), lysyl oxidase (LOX), metalloproteinases (MMP-2 and -9) and their inhibitors (TIMP-1 and 2) were measured by Northern blotting and/or real-time PCR. In tendon, expression of TGF-beta-1 and collagens I and III (but not CTGF) increased in response to all types of training. Similarly, enzymes/factors involved in collagen processing were induced in tendon, especially LOX (up to 37-fold), which could indicate a loading-induced increase in cross-linking of tendon collagen. In skeletal muscle, a similar regulation of gene expression was observed, but in contrast to the tendon response, the effect of eccentric training was significantly greater than the effect of concentric training on the expression of several transcripts. In conclusion, the study supports an involvement of TGF-beta-1 in loading-induced collagen synthesis in the muscle-tendon unit and importantly, it indicates that muscle tissue is more sensitive than tendon to the specific mechanical stimulus.