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The Mechanism of
Tissue Injury and
Healing
Dr. Eyob Manuel
lecturer / PT / DPT
Physiotherapy department
Defense college of health science

Injury Mechanisms
Athletes Usually sustain larger than usual force during
both training and competition.
1. Potential Injurious forces applied to the body act
at a different angles, over different surface areas,
and over different periods of time.
2. The human body is composed of many different
types of tissue which respond differently to applied
forces.
3. Injuries range in severity.

Force and its Effects
When a force is sustained by the tissue of the human
body, 2 primary factors are:
- The size or magnitude(AMOUNT) of the force
- The material property of the involved tissue.
- When load is applied to either the elasticity of the tissue
will absorb it or
- if the load is beyond the capacity of the tissue deformity
occurs where the tissue can not return to its original state.
THIS IS Injury.

Anisotropic tissues:
structure is stronger in resisting force from one
direction than from other.
- Lateral Ankle/ Medial Ankle sprains
- Anterior Shoulder/ Posterior Shoulder
Directional forces that can cause Tissue Injuries:
- Axial Loading/ compressive force
- Tension /Tensile force
- Shear force

 Axial loading or compressive force
 Parallel forces in same directions
 Tension or tensile force
 Parallel forces in opposite directions
 Shear force
 Perpendicular forces in opposite directions

- It is a high magnitude of stress rather than a
high magnitude of force which causes
injury.
- Strain:
- Amount of deformation with
respect to the original
dimensions of the structure or the
tissue.
- Acute injuries are caused by a single force:
Its called Macrotrauma.
- Stress Injuries are caused by repeated
loading :Its called Microtrauma.

- Tendons, Ligaments, Muscle and Bone tend to
respond to gradually increased mechanical stress
by becoming larger and stronger.
- Gradual increase in training is KEY!
- Overuse syndrome and stress fractures result
from the body’s inability to adopt to an
increased training regiment.

- Skin, Tendon and Ligament are known as
collagenous tissues after their major building block:
Collagen.
- They stretch slightly under tension loading but
they are relatively inelastic.
- Tendons connect muscle to bone
- Ligaments' connect bone to bone.
- Ligaments contain more elastin than tendons.

Skin Injury Classification
Abrasions: minor, common, cause by shear
Blisters: Repeated application of shear in one or more
direction.
Skin Bruises: Compression injury from a blow to the
underlying capillaries.
Incisions, Lacerations, Avulsions and Punctures:
breaks in the skin resulting from injury.

Other soft tissue Injuries
- Contusions:
- Hematoma: Hard mass composed of blood and
dead tissue.
- Tendon Tear: Begins to develop tears when it is
stretched 5-8% beyond normal length.
- strain/ sprain: 3 degrees.
- Myosities: inflammation of the connective tissue of
muscle.
- Fasciitis: inflammation of the sheaths of fascia
surrounding portions of a muscle.

Tendinitis: inflammation of the tendon.
Tenosynovities: Inflam. of the sheath of a tendon.
Bursitis: irritation or inflammation of one or more bursa
Myosities Ossification: Common one quadriceps.
Calcific Tendonitis:
bone mineral deposit accumulation.
.

SOFT TISSUE HEALING
3 Phase process of tissue healing.
1. Acute Response or inflammatory phase
2. Repair and regeneration phase
3. Remodeling phase
When it is acceptable to return an athlete to
practice and competition require
knowledge and understanding of the
healing process.

Acute Inflammatory phase
Also Known as reaction phase:
- The first several days after the injury.
- pain, swelling, Redness(hypermia),
local heat(hyperthermia), some times loss of
function.
- Vasoconstriction: lasting from few seconds to
as long as 10 min.
-VC: causes also Hypoxia, Necrosis
- Vasodilatation is brought on by Heparin
(anticoagulant)
- Swelling and Hematoma
- This creates THE ZONE OF PRIMARY INJURY

- Leukocytes, mast cells, platelets, Plasma are
released to the injury site.
- This chain of chemical activity produces the ZONE
OF SECONDARY INJURY.
- After the ingested of the dead tissue by the white
blood cells (phagocytosis), the leukocytes re
enter
the blood stream and the acute inflammatory
reaction subsides.
- First Phase Over!

Repair and regeneration Phase
Two days after injury – through the next 6-8 weeks.
- Some overlap from the later phase.
- Hematoma decreases to allow new tissue to grow.
- The Skin regenerates new tissue, but other soft
tissues replace damage cells with SCAR TISSUE.
- 4th
to 5th
day after injury, a weak vascular
connective tissue gets produced over the injury
area.
- Scar tissue: Inelastic, non-vascular, less functional,
30% less tensile strength than the pre-injury soft
tissue.

Remodeling Phase
 Final phase
 Maturation of the newly formed tissue.
 Increased organization of extra cellular matrix and
return to normal histochemical activity.
 In soft tissue, the process takes from 3 wks to 1 yr or
more. Also overlaps.

› DO YOU KNOW?
 Following sever injury, muscle may generate
only about 50% of its pre-injury strength.
 Tendon’s and Ligaments have few
reparative cells, healing takes more than 1yr.
› If tissue goes under high tensile stress before scar
formation is completed, the new tissue will be
elongated causing joint instability.
› Ligaments have more elasticity than tendons but
the tears is most of the time due to joint
dislocations.

 Longitudinal bone growth continues as long
as the epiphyseal plates or growth plates
exist.
› Shortly after adolescence, the plate disappears
and the bone fuses. (18 years of age mostly)
› Bone continue to grow in diameter through out
the lifespan.
› Calcium carbonate, calcium phosphate,
collagen are the primary constituents(ingredient
or element).
 Osteoblast and Osteoclast
BONE INJURIES

Bone Injury Classification
 Simple(closed): clean break but no break on the skin.
 Compound (open): bones end penetrate skin
 Greenstick: break is incomplete.
 Transverse: strait line break across.
 Oblique: diagonal line break across.
 Spiral: “ S” shape break due to excessive torsion
 Comminuted: bone breaks in to several pieces.
 Impacted: bone to bone impaction
 Depressed: occurs frequently on flat bone portion
where it is driven inwards.
 Avulsion: bone pulled off at the muscle or ligament
attachment
 Epiphyseal: separation of the epiphyseal.

Bony Tissue Healing
 3 stages.
Acute inflammatory phase: up to 4 day.
Vasodilatation, edema, histochemical
formation.
 Repair and regeneration phase:
- Osteoclast reabsorbs damaged bone tissue
- Osteoblast builds new bone tissue
- Callus forms: weak immature bone tissue,
strengthens in time.
- If bone is lined up callus does not form. It
heals normal.

Remodeling bone tissue:
- Osteoblast activity, Continues until
normal shape is restored and bone
strength is normalized for the load it is
designed to handle.
The whole process of Bone healing
depends on age , gender and past
Medical history.
In a normal circumstances it is 4-8 weeks
post injury.

Nerve Injury Classification
 Injury is common with Tensile and compression
force.
› Contact sports, automobile accident.
› Nerve roots on the spinal cord, more
susceptible to injury because they are not
protected with connective tissue.
› Loss of sensation or motor control.
 What are the mechanism of injuries?

Nerve tissue Healing
 Completely severed: Permanent
damage, unless surgically repaired.
 When nerve fibers get rupture in a
tensile force and the surrounding
sheath is sound, regeneration is
possible.
 Slow rate regeneration, 1 mm per day
or 2.5 or 3 cm per month.
 1CM=10MM

 It is very important for Personnel who are
involved with athletes to have a good
understanding of tissue healing in order to
prevent further problems after injuries
regarding their athletes.
 The Body has its own way and time frame
of healing and should not be rushed.
“NO PAIN NO GAIN“
Is it really true?

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