Injuries to tendons vs ligaments show many similarities, but there are noticeable differences in the types of injuries and the reasons. There are approximately ligaments in the human body , from a ligament in the foot all the way up to the neck and jaw.
While ligaments are essential to help prevent friction between bones, they have a limited stretch capacity. Sprains can happen as a result of a significant collision or blow, an overly sharp or violent twisting of a joint, or from a particularly forceful fall.
Sprains can be incredibly painful and debilitating. They range from a relatively mild hyperextension to a partial tear, or to a severe sprain, where a complete ligament tear leaves the joint totally unsupported. Even repeated mild sprains in one joint can result in the ligament becoming attenuated, meaning it loses the ability to properly heal and cushion the joint.
Though they are more elastic than ligaments, they can also be damaged by overstretching, sometimes leading to a tear. In many cases, tendon injuries are the result of overuse from repetition. Repetitive athletic movements, like those in golf, tennis, baseball, and other sports, often result in a tendon strain or tendonitis. Repetitive movements that lead to injury are not exclusive to sports activities and also frequently occur in some occupations such as the construction and manufacturing industries, where continued stress on the tendons can lead to strains or tendonitis.
In some instances, a snap may be felt or pop might be heard or felt at the time of injury due to subluxation. Subluxation occurs when a tendon slips or moves from its normal position caused by trauma to the tendon. One of the reasons it can be difficult to tell the difference between an injury to a tendon vs ligament is that both have similar symptoms, such as pain, inflammation and a potential decrease in range of motion. Sometimes sprains and strains are so mild a person barely notices the slight discomfort and continues to engage in activity that places additional stress on the soft tissue.
Unfortunately, x-rays do NOT show tendon or ligament injuries. X-rays are mainly designed to show injuries to bones and joints, but not soft tissue areas like tendons, ligaments, or cartilage, according to the American Academy of Podiatric Sports Medicine AAPSM. Physicians are sometimes able to diagnose tendon strains or tendonitis by examining a patient, reviewing the symptoms, and considering their recent physical activity.
Injuries to tendons and ligaments can be very painful. A person may even mistake the injury for a broken bone. It is very difficult to self-diagnose the injury or to tell the difference between tendon and ligament injuries based on the symptoms alone. Although many minor tendon and ligament injuries heal on their own, an injury that causes severe pain or pain that does not lessen in time will require treatment.
A doctor can quickly diagnose the problem and recommend an appropriate course of treatment. Untreated tendon and ligament injuries increase the risk of both chronic pain and secondary injuries.
People should seek prompt medical care rather than ignoring the pain. A lateral collateral ligament LCL sprain occurs when there is a tear in the ligaments on the outside of the knee. Causes include sports injuries and…. Doctors perform tendon repair surgery to fix a tendon injury. Tendons are tough, stretchy tissues that join muscles to bone. Their job is to allow the…. Extensor tendons connect muscle to bone and are located just under the skin. They are poorly protected by fat and therefore prone to injury.
This MNT…. Hamstring tendonitis is a swollen or injured hamstring tendon. Symptoms include pain in or near to the knee joint. The type of treatment will depend…. Tendons and ligaments: What is the difference? Medically reviewed by Marina Basina, M. Differences Injuries Treatment Summary Tendons and ligaments are fibrous bands of connective tissue.
What are tendons and ligaments? Share on Pinterest Tendons and ligaments both play a key role in allowing movement. Injuries that affect them. Collagen fibers, with a typical length of 0.
Within the packing of the collagen fibers are distinct gaps sometimes called hole zones Fig. The structure of these holes is currently the focus of some debate. In one model, the holes are completely isolated from each other. In another model, the holes are contiguous and together from a groove about 0.
Within these holes mineral crystals form. The mineral crystals in final form are believed to be made from a carbonate apatite mineral called dahllite which may initially resemble an octacalcium crystal. The octacalcium crystal naturally forms in plates. These mineral plates are typically 0. It is these plates which are packed into the type I collagen fibrils. Because of the nature of the packing, the orientation of the collagen fibrils will determine the orientation of the mineral crystals.
One such model is provided by Weiner and Traub shown in Martin et al. Trabecular Bone Structure. Trabecular bone is the second type of bone tissue in the body. It fills the end of long bones and also makes up the majority of vertebral bodies. As with cortical bone, we will organize trabecular bone structure according to physical scale size.
Trabecular Bone Structural Organization. Level Trabecular Structure Size Range h. A - denotes structures found in secondary trabecular bone. B - denotes structures found in primary trabecular bone. C - denotes structures found in woven bone.
D - trabecular packets fall in between the 1 st and 2 nd level scalewise. Table 2. Trabecular bone structural organization along with approximate physical scales. The major difference between trabecular and cortical bone structure is found on the 1 st and 2 nd structural levels.
It should be noted that the 3 rd level of trabecular bone structure is the same as far as we know as cortical bone structure. The major mechanical property differences as far as we know between trabecular and cortical bone are the effective stiffness of the 0 th and 1 st structural level.
Trabecular bone is more compliant than cortical bone and it is believe to distribute and dissipate the energy from articular contact loads. However, trabecular bone has a much greater surface area than cortical bone.
Within the skeleton, trabecular bone has a total surface area of 7. A comparison between the general features of cortical bone and trabecular bone including volume fraction and surface area is given below Jee , :. Volume Fraction 0. Total Bone Volume 1. Total Internal Surface 3. Table 3.
Comparison of some structural features of cortical and trabecular bone. One of the biggest differences between trabecular and cortical bone is noticeable at the 1 st level structure. As seen in the first table, trabecular bone is much more porous than cortical bone.
Bone volume fraction is defined as the volume of bone tissue including internal pores like lacunae and canaliculi per total volume. The trabecular bone volume fraction varies between different bones, with age, and between species. The basic structural entity at the first level of trabecular bone is the trabecula.
Early finite element models of 1 st level trabecular structure did indeed model trabeculae using plate and beam finite elements. Trabecula are in general no greater than m m in thickness and about m m or 1 mm long. Unlike osteons , the basic structural unit of cortical bone, trabeculae in general do not have a central canal with a blood vessel.
Note: we are characterizing the basic or 1st level structural unit of trabecular bone as the trabecula based on the fact that it has similar size ranges as the osteon. Jee denotes the trabecular packet as the basic structural unit of trabecular bone based on the fact that it is the basic remodeling unit of trabecular bone just as the osteon is the basic remodeling unit of cortical bone. In rare circumstances it is possible to find unusually thick trabeculae containing a blood vessel and some osteon like structure with concentric lamellae.
Another structure found within the trabecula is the trabecular packet. We have chosen to define the trabecular packet as a 1 st level structure because of its size. The trabecular packet is only found in secondary trabecular bone because it is the product of bone remodeling in which bone cells called osteoclasts first remove bone and bone cells called osteoblasts then deposit new bone were the old bone was removed.
Trabecular bone can only be remodeled from the outer surface of trabeculae. The typical trabecular packet has a crescent shape Jee , A typical trabecular packet is about 50 m m thick and about 1 mm long.
Trabecular packets contain lamellae and are attached to adjacent bone by cement lines similar to osteons in cortical bone. The 2 nd level structure of trabecular bone has most of the same entities as the 2 nd level structure of cortical bone including lamellae, lacunae, canaliculi , and cement lines.
Trabecular bone, as noted before, does not generally contain vascular channels like cortical bone. What differentiates trabecular bone from cortical bone structure is the arrangement and size of these entities. For instance, although lamellae within trabecular bone structure are of approximately the same thickness as cortical bone about 3 m m; Kragstrup et al. Lamellae are not arranged concentrically in trabecular bone as in cortical bone, but are rather arranged longitudinally along the trabeculae within trabecular packets Fig.
Krapstrup et al. Cannoli et al. They found that the lacunae were ellipsoidal in both areas. The cross-sectional area of lacunae in trabecular bone ranged between Thus, the lamellar pattern as well as the lacunae size differ between trabecular and cortical bone.
The third level of trabecular bone structure consists of the same entities as the third level of cortical bone structure, namely the collagen fibril-mineral composite. As no detailed studies have been perfomed on trabecular bone at this level, it is presumed for now that the structure at this level, i. Ascenzi , A. Biomechanics, Balazs ed. Chemistry and molecular biology of the intercellular matrix, Academic Press, New York. Ashman, R. Biomechanics, 22 Cane, V. Tissue Int. Choi , K.
Biomechanics, 25 Biomechanics, 23 Christel , P. Ciarelli , M. Currey , J. European Society of Biomechanics, Gibson, L. Biomechanics, 18 Giraud-Guille , M. Goldstein , S. Biomechanics, 20 Jee , W. In: Weiss, L. Histology: cell and tissue biology 5th ed. Katz, J. Krapstrup , J. Bone Dis. Kuhn, J. Marotti , G. Proposal for a new model of collagen lamellar organization", Arch. Martin, R. Mente , P. Reilly, D. Schaffler , M. Snyder, B. Weiner, S. Structure and Function of Ligaments and Tendons I.
Overview Ligaments and tendons are soft collagenous tissues. Hierarchical Ligament and Tendon Structure We start out again emphasizing that ligaments and tendons have a hierarchical structure. One schematic of this hierarchical structure is taken from your text, and is a very famous schematic from Kasterlic : The largest structure in the above schematic is the tendon shown or the ligament itselt.
Tendons contain fibroblasts biological cells that are arranged in parallel rows Basic Functions 1. They carry compressive forces when wrapped around bone like a pulley Type I Collagen: 1. Fibroblasts Blood Supply 1. Nutrition for cell population; necessary for matrix synthesis and repair III.
General overview of ligament and tendon mechanics As with all biological tissues, the hierarchical structure of ligaments and tendons has a signficant influence on their mechanical behavior. Nonlinear Elasticity If one neglects viscoelastic behaviour , a typical stress strain curve for ligaments and tendons can be drawn as: There are three major regions of the stress strain curve: 1 the toe or toe-in region, 2 the linear region and 3 the yield and failure region.
Creep is illustrated schematically below: The second significant behavior is stress relaxation. This behavior is illustrated below: The other major characteristic of a viscoelastic material is hysteresis or energy dissipation. An example of hysteresis is shown below: The two figures above show that the amount of hysteresis under cyclic loading is reduced and eventually the stress-strain curve becomes reproducible. A schematic of such a test setup from the text is shown below: The grips are placed around the bones of the joint to give a much more secure fit.
The strain energy function is given below: where Ii are the invariants of the right Cauchy deformation tensor. The 2nd Piola-Kirchoff stress tensor is calculated from the above strain energy function by the relationship: Two recent papers have used the more common isotropic form of the strain energy function for analyzing stress and strain in anteior cruciate ligamens.
It is given below: where I1 and I2 are invariants of the right Cauchy Deformation tensor. There are defined as: Thus, we can rewrite W using the explicit form of the invariants I1 and I2 as: where a1 and a2 are constants to be determined experimentally.
First we know the relatonship between E11 and C11 is: The derivative can be taken using the chain rule as: We can rewrite the above equation in terms of E using the general equation relating E to C the right Cauchy Deformation Tensor : This gives S11 in terms of E as: To plot S11 vs.
This strain energy function is given below: where I1 and I2 are the 1st and 2nd invariants of the Green-Lagrange strain tensor, e is the exponential function, and a1,a2,a3 are constants to be experimentally determined. Based on our previous expansion of the invariants, we write the strain energy function directly in terms of the Green-Lagrange strain tensor components as: To calculate the S11 component of the 2nd Piola-Kirchoff stress, we again take the derivative of W with respect to E We can then plot a stress-strain curve using the values for the experimental coefficients a1 ,a2 and a3.
A schematic drawing showing this change in material properties with age is shown below: You can see from this graph that as the strength of the ligament insertion increases, failures change from being avulsion failures to being mid-substance failures. A quantitative example of the increase in mechanical properties with maturity is shown in the graph from your text below: While increasing age from child to adult also increases the mechanical properties of ligaments and tendons, further increasing age from young adulthood decreases the properties of ligaments and tendons.
Mechanically Mediated Ligament and Tendon Adaptation: Immobilization versus Exercise Ligaments and tendons are adapted in response to changes in mechanical stiffness. Affects on the stress strain curve from Woo are shown below: If the rabbits became active, there was an increase in stiffness and strength almost back to the level of controls. This hypothesis from the text is shown below: As you can see, immobilization has a more rapid and substantial affect on mechanical properties than does increased load from exercise.
The change in strength over time is shown in the figure below group 1 is the early mobilization without repair, group 2 is repair with 3 week immobilization and group 3 is repair with 6 week immobilization : These results demonstrate two basic concepts: 1 in a confirmation of tissue structure function relationships, the stiffness and strength of healing ligaments correlates with the type and amount of collagen fibrils present, and 2 that mechanical stimulus has a significant affect on ligament structure.
Cartilage Structure and Function I. Overview There are three major types of cartilage in the body: 1 hyaline cartilage, 2 fibrocartilage , and 3 elastic cartilage. Diarthroidal Joint Anatomy and Hierarchical Cartilage Structure Again, although it begins to sound redundant at this point, articular cartilage itself has a hierarhical structure and is also part of a diarthroidal joint which is a composite structure.
The nature of the hierarchical structure of both diarthroidal joints and articular cartilage is illustrated in the figure from your text shown below: The top row of the figure illustrates the composite strcuture of diarthroidal joints which consist of bone, articular cartilage, ligaments, tendons, muscle and the joint capsule.
Structure-Function Relationships in Articular Cartilage and Meniscus As perhaps can be gleaned from the previous sections, there are three major factors that contribute to articular cartilage mechanical behavior.
Solid Matrix Properties First, let us consider the tensile properties and behavior of the cartilage solid matrix. Thus, this matrix follows the classic nonlinear stress strain curve for soft tissues as shown below: where we see a toe region, a linear region, and a failure region. A typical dumbell specimen is used to test the matrix tensile properties as shown below: In terms of structure function relationships, we can see the effect of increasing collagen content on tensile properties by looking at the tensile moduli from the linear portion of the above stress strain curved measured in the different cartilage zones.
Let us consider the following strain energy function: where k and B are constants and E is the Green-Lagrange strain. Compressive Fluid-Solid Properties As was mentioned in the section of cartilage composition, the interaction between the fluid and solid phase of the cartilage plays a significant role in the mechanical behavior of cartilage.
Thus, the units work out as: The permeation speed V is related to Q by dividing Q by the A times the volume fraction of the fluid. The diffusive drag coefficient, how much drag the fluid creates on the solid, determined as: where K is the drag, k is the permeability and the remaining term is the volume fraction of fluid.
The tenets of biphasic theory are the following: 1. Energy dissipation is result of fluid flow relative to solid matrix. The standard stress equilibrium equations are modified for biphasic theory as follows: where is the solid stress, is the fluid stress, K is the drag coefficient, is the solid velocity and is the fluid velocity.
As example of the behavior of cartilage under compression from the text is shown below: In this case, cartilage is subjected to a fixed displacement at point B. Constitutive Properties of Other Soft Tissues Overview As mentioned often in class, many soft tissues have the same general nonlinear stress-strain curve as those we have seen for ligaments, tendons, blood vessels, and the cartilage solid matrix. This nonlinear stress-strain relationship is illustrated schematically below: Where S is the 2nd Piola-Kirchoff stress and E is the Green-Lagrange strain.
Skin Skin is the largest organ in the body. It has the same general nonlinear stress-strain curve as other soft tissues. Tong and Fung characterized soft tissue mechanics using a strain energy function of the form: where As with any other strain energy function, to determine the 2nd Piola-Kirchoff stress as a function of the Green-Lagrange strain for skin, we differentiate the strain energy function with respect to the appropriate Green-Lagrange strain component.
Thus, to determine stress components for the skin we have: Lets look at an an example of calculating S11 using the above strain energy function. Miller and Chinzei used a platen loading device to test samples of brain tissue as shown below: Due to the delicacy of the brain tissue, only one load cycle was applied for specimen.
A typical stress-strain curve for brain tissue at the slowest loading rate along with the model fit from Miller and Chinzei is shown below: For finite deformation of brain tissue, Miller and Chinzei proposed the following strain energy function: It is important to note, that in constrast to strain energy functions we have studied so far, this one is a function of the Left Cauchy Deformation tensor not the Right Cauchy Deformation tensor.
This model relates stress S to the principal stretch ratios l as: where g and a are constants that are fit to experimental data. Trabeculated Myocardium A classification of soft tissues for which material models have only recently been developed is that of muscle tissue. An example of the trabeculated microstructure from Xie and Perucchio is shown below: Thus, to determine the overall or effective behavior of the trabecular myocardium, Xie and Perucchio assumed a strain energy function for the myocardial microstructure, based on earlier work by Taber: where A, B and Cf are experimentally determined constants, I1 is the first invariant of the Green Lagrange strain tensor, and eff is the Green-Lagrange strain in the direction of the muscle fiber.
This general approach can be written as: where Wp is the strain energy function written for the passive properties and Wa is the strain energy function written for the active for generation capability. Xie and Perucchio proposed the following passive and active strain energy functions: In the active strain energy function Wa , the normal strains are used as a scaling factor to represent alignment and stiffening of muscle fibers with increasing strain.
To compute the experimental constants a1 - a7, Xie and Perucchio simulated the response of the trabeculated myocardium assuming the microstructural material properties being subject to a biaxial state of strain, and the third direction of strain fixed to zero: where e ij are components of the Green-Lagrange strain tensor.
The corresponds to the boundary conditions illustrated below: An additional set of boundary conditions was then used to test the fitting of the first boundary condition representing uniaxial stretch. An example of the numerical model from Xie and Perucchio is shown below: After running the numerical simulation, computing the average 2nd Piola-Kirchoff stress and Green-Lagrange strain, an optimization procedure was used to compute the coefficients for the proposed material model.
The optimization model computes the model coefficients such that the stress computed from the material model matches that from the finite element calculation: where the components of the 2nd Piola-Kirchoff stress tensor are computed as usual by differentiating the strain energy function with respect to the Green-Lagrange strain components: The results showing stress strain behavior for both passive and active tissue under biaxial deformation is shown below: The results showing the data from the numerical simulation and the optimal fit for the uniaxial case is shown below: In this work, the finite element calculation plays the role of the mechanical test.
A General Proposal for a Strain Energy Function Due to the consistent nature of soft tissue nonlinear mechanical behavior, Fung proposed a general form of a strain energy function that could be adapted to any soft tissue.
This general strain energy function contains the two major features of any strain energy function we have examined so far: a measure of deformation and constants to be fit to experimental data: where a , b , g and k are all constants to be experimentally and E is the Green-Lagrange strain tensor. Overview Although we don't often view them in this context, blood vessels are subject to mechanical stress during the pumping of blood.
Blood Vessel Structure In general the circulatory system of blood vessels may be broken down into those vessels that deliver oxygenated blood to tissues: the arteries, arterioles, and capillaries, and those vessels that return blood with carbon dioxide for gas exchange: the veins and venules. The basic structure of all these vessels can be broken down into three layers: 1. The Adventia It is the materials that make up these layers and the size of these three layers themselves that differentiates arteries from veins and indeed even one artery from another artery or one vein from another vein.
A schematic from Fung's "Mechanical Properties of Living Tissues" shown below gives an overview of the different structures in the different types of blood vessels: Although a little bit difficult on the reproduced schematic, arteries have a large media layer than veins. Here is the composition of each layer of a blood vessel: Intima : Innermost layer Contains endothelial cells Basal lamina 80 nm thick Subendothelia layer with collagenous bundles, some elastin Media: Middle Layer Contains mainly smooth muscle cells Collagenous fibrils type III collagen Divided from adventia by elastin layer elastin is a protein which is very elastic, can undergo a stretch ratio of 1.
Blood Vessel Mechanical Characterization and Structure-Function Once we know something about tissue structure, the next natural question is: How does this structure contribute to mechanical function?
We can see this in stress strain curve from a human vena cava below: Another critical aspect of blood vessel behavior is residual stress.
A figure from Fung below shows that different amounts of residual stress are present in different arteries: If we desire a more quantitative description of blood vessel mechanics than toe versus linear region, than we can model the blood vessel as a pseudoelastic material using hyperelastic strain energy functions. An example of a test set-up to test blood vessels from Fung's laboratory is shown below: The test set-up allows for torsional , tensile and pressure testing. The first form often used is the polynomial form, given below in terms of cylindrical Green-Lagrange strain components: where A1 through A7 are material constants and the strains are the same as those described above.
The second form uses an exponential function: The above forms neglect shear stress, assuming a very thin vessel. To calculate the stress components, we differentiate the strain energy function with respect to the strain components: As can be expected from differences in tissue structures, there are differences in the constants for the strain energy functions for different arteries.
Let us use the following constants in the above stress relation for the plot: Artery C KPa a1 a2 a4 Carotid 2. We get the plot shown below: We see that C increasing C slightly shifts the curve to become stiffer, along almost the whole graft. Mechanically and Disease mediated Blood Vessel Adaptation There primary ways that blood vessel tissue structure changes in through aging, disease, and change in mechanical load.
Fung presents the changes in material properties based on the strain energy function shown below: where a1, a2, a4, and C are material constants, and E11 and E22 are components of the Green-Lagrange strain tensor. Again, we obtain the second Piola-Kirchoff stress tensor if we differentiate the strain energy function with respect to the strain: For the above strain energy function, we obtain the stress component S11 for example as: were we see that stress is definitely a nonlinear function of strain with the higher order terms and the exponential.
Although he did not report changes in tissue structure in the text, he noted profound changes in the nonlinear stress strain curve and the material constants in the strain energy function for the diabetic rats, with their aorta becoming stiffer, as shown below: You will also note that the constants in the strain energy function change significantly. The histological changes that Fung saw are shown below: In terms of mechanical properties, Fung reported the change in opening angle of the artery, a measure of the change in residual stress.
Bone Structure I. Overview We start our section on tissue structure function and mechanically mediated tissue adaptation with bone tissue. Cortical Bone versus Trabecular Bone Structure Bone in human and other mammal bodies is generally classified into two types 1: Cortical bone, also known as compact bone and 2 Trabecular bone, also known as cancellous or spongy bone.
A schematic showing a cortical shell around a generic long bone joint is shown below: The basic first level structure of cortical bone are osteons. Hierarchical Structure of Cortical Bone As with all biological tissues, cortical bone has a hierarchical structure. A general view of cortical bone structure showing some of the 1st and 2nd level structures is shown below: III. In the figure below from Martin and Burr lamellar bone is shown on the top while woven bone is shown on the bottom: Plexiform bone arises from mineral buds which grow first perpendicular and then parallel to the outer bone surface.
The structure of lamellar bone is still widely debated, so we will discuss here the competing theories III. Trabecular Bone Structure Trabecular bone is the second type of bone tissue in the body. A comparison between the general features of cortical bone and trabecular bone including volume fraction and surface area is given below Jee , : Structural Feature Cortical Bone Trabecular Bone Volume Fraction 0. Tendons consist of densely packed collagen fibers.
Muscles, either individually or in groups, are supported by fascia. Fascia is strong sheath-like connective tissue. The tendon that attaches muscle to bone is part of the fascia. George A. Frey focuses his medical practice on the treatment of all complex spine problems affecting the cervical, thoracic, and lumbar regions in adult and pediatric patients.
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