what biomechanics is and why it's important in understanding ligaments and tendons. structure and composition of ligaments and tendons. the roles of ligaments and tendons in the body and how they contribute to movement and stability. mechanical properties of ligaments and tendons, including strength, elasticity, and viscoelasticity.

1. Biomechanics of tendon and
ligament
By : Jemini Parmar
F.Y.MPT

2. The principal joint stabilizing connective
tissues
Tendon , Ligaments & joint capsules
The passive structures
Surround, connect & stabilize the joints of skeletal system
Provide static stability to the joints

3. The principal joint stabilizing connective
tissues
Ligament & joint capsule
Connect bone to bone
The static restraints
Augment the mechanical
stability of the joints
Guide joint motion
Prevent excessive motion
Provide joint sense to nervous
system

4. The principal joint stabilizing connective
tissues
Tendons
Attach muscle to bone
The dynamic restrains & protect from
instability
Transmit tensile loads from muscle to
bone
The muscle tendon unit …..active
structure

5. Structural composition of tendons
Dense connective tissues(parallel-fibered
collagenous tissues)
Provide strength & flexibility
Consist of relatively few fibroblast (tenocytes)
& extracellular matrix
Cellular material – Approx 20% of the total
tissue volume
Extracellular matrix - Approx 80%

6. Tendons ….
Tendons cells(tenocytes)
Specialized fibroblast within the tendon substance
Function of tenocytes
Control tendon metabolism
Mechanotransduction ….collagen synthesis
Tenocytes lie in longitudinal rows along fibrils
Have multiple extensions in ECM , allowing for three dimensional
communication via gap junctions

7. Tendons ….
The extracellular matrix(ECM)……..
Water – Approx. 55 to 70% of the matrix
Solids – 30 to 45%(collagen 60 to 85%, inorganic substance <0.2%, a
small amount of elastin 2% & other proteins 4.5%)
Maintain tendon structure
Facilitate biomechanical response to mechanical loading

8. Tendons ….
The collagen content….
60% type 1 fibres
Type 3, 4, 5 & 6 also present
Type 1 sustains large tensile loads
Some level of mechanical deformation

9. Collagen synthesis
• Process starts in tenocytes
Integrins ..sense tensile strain &
transform into adoptive responses of
cells called mechanotransduction
Growth factors
TGF-β, IGF, IGF-BP, FGB et.
IL & PGs are also involved
MAPK(mitogen-activated protein
kinase pathway)

10. Collagen synthesis
Fibroblast procollagen
extracellular collagen
Type 1 collagen molecule….
The most common collagen
molecule
Consist of 3 polypeptide
chains (α chains) in a triple
helix ….Rod shaped
Length – Approx 280nm
Diameter - Approx 1.5nm

11. Intra- & interchain bonding is essential for
the stability of the molecule
Cross -linking between collagen
molecules….
Essential for the strength of the
tissues they compose
Allows these tissues to function
under mechanical stress
“head-to-tail” inter-actions

12. Intra- & interchain bonding is essential for
the stability of the molecule
Cross-linking in immature collagen….
Relatively few & reducible
Soluble in neutral salt & in acid solutions
Cross -linking in mature collagen….
Stable and nonreducible cross-links by glycation
Not soluble in neutral salt or in acid solutions

13. Schematic representation of the
microarchitecture of a tendon.

14. Collagen ….
The arrangement of the collagen
fibers differs somewhat in the tendons
and ligaments and is suited to the
function of each structure .
Arrangement of collagen fibers in
tendons….
Parallel arrangement
To bear high unidirectional tensile load
during activity

15. Elastin
Proportion of elastin mechanical properties of tendons &
ligaments
Protein elastin in tendons & extremity ligaments are very less 2%.
In elastic ligaments (lig.flavum)….relatively high
2 to 1 ratio of elastic to collagen fibers in ligamentum flavum

16. Ground substance
Ground substance in ligaments & tendons….
Composed of inorganic substances , 0.2% & other proteins 4.5%
Inorganic substances….
Proteoglycans (PGs)most dominant protein
Only a small number of PGs exist in tendons
PGs make the matrix a gel-like material
PGs act as a cement like substance between the collagen microfibrils
to stabilize the collagenous skeleton and contribute to the overall
strngth

17. Composition and structure of ligaments
Ligaments have same general
composition as tendon with few key
differences
In contrast to tendons
Closely interlaced with one another
Sustain multidirectional tensile loads

18. Vascularity
Limited vascularity
Blood vessels in tendons accounts for 1-2%(white appearance)
Other factors such as location , morphology , prior injury & level of
physical activity also contribute
Tendons receive their blood supply directly from vessels in the
perimysium , the periosteal insertion , and the surrounding tissue
Vascular tendons…. Tendons surrounded by sparatenon
Avascular tendons…. Tendons surrounded by a sheath

19. Neural components of tendon & ligament
Have specialized nerve ending and mechanoreceptors
Provide proprioception and nociceptors

20. Outer structure of Tendons vs Ligaments
The paratenon/epiligament ….the outer loose areolar connective
tissues
Paratenon prtects the tendon and enhance its gliding
The epitenon ….a synovial like membrane just beneath the paratenon
in tendons subjected to high friction forces
Facilitates gliding of the tendon
The endotenon….bind each fiber bundle together , which continues
at the Musculo-tendinous junction into the perimysium

21. Insertion into bone
The tendo-osseous junction….
Similar in ligaments and tendons
Consists of four zones
Zone-1 : parallel collagen fibers
Zone-2 : unmineralized
fibrocartilage
Zone-3 : mineralized fibrocartilage
Zone-4 : cortical zone

22. Biomechanical Properties of Tendons and
Ligament
Viscoelasticity
Tendons and ligaments are viscoelastic structures
Tendons are strong enough to sustain the high tensile forces
The ligaments are pliant and flexible, allowing natural movement of
the bones to which they attach, but are strong and inextensible so as to
offer suitable resistance to applied forces.

23. load-elongation curve
A load-elongation curve offers
information regarding the tensile
capacity of a tendon-ligament
structure after loading a tendon or a
ligament to failu
The ultimate load (N) is the highest
load placed on the structure before
failure.
The ultimate elongation (mm) is the
maximum elongation of the complex
at failure.

24. The uploaded collagen fibers have a wavy configuration. The collagen fibers straightened out under load.

25. load-elongation curve of ligaments with
high level of elastin

26. Hysteresis
During the loading and unloading
of a ligament between two limits of
elongation , the elastic fibers allow
to its original shape and size after
being deformed. Meanwhile part of
this energy spent is stored. And this
cycle is called as hystresis.
The area enclose by the loop
represents the energy loss.

27. Viscoelastic behavior in tendons and
ligaments to tensile loads
• Both ligaments and tendons display this viscoelastic behavior that is
assumed to result from the complex interaction of its constituents (i.e.,
collagen, water, surrounding protein, and ground substance)
1. Load relaxation 2. The creep response

29. Tendon injuries

30. Ligament injuries

31. Healing of tendons and ligaments
Three phases occurring in succession:
The inflammatory phase
The proliferative phase or fibroplasia
Remodeling and maturation phase
There is also variation in the ability of tendons and ligaments to
heal.

32. Factors That Affect the Biomechanical
Properties of Tendons and Ligaments
Maturation and aging
Pregnancy and the postpartum period
Mobilization and immobilization
COMORBIDITIES : diabetes mellitus, connective tissue disorders
PHARMACOLOGIC AGENTS : steroids , nonsteroidal anti-
inflammatory drugs (nsaids) ,

33. Thank you