Physiology of trauma and healing

What do these terms mean when it comes to tissue properties?

• Load

• Stiffness

• Stress

• Strain

• Load

  • An external force acting on the body causing internal reactions within the tissues

• Stiffness

  • Ability of a tissue to resist a load

  • Greater stiffness = greater magnitude of load it can withstand

• Stress

  • Internal resistance of tissue to a load

• Strain

  • Extent of deformation of tissue when it is loaded

What does elasticity allow for in human tissue? What is the yield point?

• Allows tissues to return to normal length following deformation

• Tissue is deformed to an extent that it no longer reacts elastically

• Beyond yield point, deformation continues even after load is removed

  • Permanent/plastic changes to tissue

• If yield point is exceeded, mechanical failure occurs resulting in damage to the tissue

What do the following terms mean?

Compression

Tension

Shear

• Compression

  • A load that produces a crushing or squeezing type force

• Tension

  • Force in the opposite direction, pulling or stretching the tissues

• Shear

  • Equal but not directly opposite loads are applied to opposing surfaces

  • Tends to cause sliding or displacement

Traumatic/Acute vs Overuse/Chronic injuries?

Traumatic/Acute

• Direct blow or an event that initiates the injury process

• E.G

  • Contusion

  • Ligament sprain

  • Muscle strain

  • Bone fracture

  • Joint dislocation

Overuse/Chronic

• Injury doesn’t heal properly and often results from repetitive dynamic use over time (Running, jumping, throwing, etc.)

• E.G

  • Tendinopathies

  • Osteoarthritis

  • Stress fracture

  • Muscle soreness

What are the different kinds of musculotendinous unit injuries?

1. Muscle strains

2. Muscle soreness

3. Tendon Injuries

4. Myofascial trigger points

5. Contusions

What are muscle strains? What do each of the grades mean?

• Stretch or tear of a muscle or tendon

• MOI: Tension force

• Most common site for tears is near the musculotendinous junction

• Graded on a 3-point scale

• Grade 1 - Mild

  • Pain

  • Full ROM

  • No decrease in strength

• Grade 2 - Moderate

  • ~50% torn

  • Pain, swelling

• Grade 3 - Severe

  • Completely torn

  • Significant pain and swelling

  • No AROM or strength

What is Muscle Soreness? What are the 2 types?

• Overextension in strenuous exercise resulting in muscular pain

• Generally occurs following participation in an activity individual is unaccustomed to

• 2 Types

  • Acute-Onset Muscle Soreness

    • Accompanied by fatigue, transient pain, experienced immediately after exercise

  • Delayed-Onset Muscle Soreness

    • Pain that occurs 24-48hrs following activity that gradually subsides

    • Potentially caused by slight microtrauma or connective tissue structures

    • Prevent soreness through gradual build-up of intensity

What are some key points about tendon injuries?

• Parallel collagenous fibers organized in bundles

• Can produce 8700 to 18000 pounds per square inch → very strong

• Collagen straightens during loading but will return to original shape after loading

• Breaking point occurs at 6-8% of increased length

• Tendon usually 2x strength of muscle it serves

  • T/F Tears are commonly at muscle belly, musculotendinous junction, or bony attachment

• Chronic overuse injuries involving tendons represent 50% of all sports injuries

What does tendinopathy mean?

• Umbrella term for pathology of the tendon

• Refers to pathological condition with pain and thickening of the tendon

• Onset and continued pain are a result of changes in typical loading patterns, inappropriate loading volume or frequency

• Most common at Patellar tendon, Achilles tendon, Rotator cuff, or lateral epicondyle

• Can refer Tendinitis or Tendinosis

  • Tendinitis = inflammation of tendon

  • Tendinosis = microtears or degeneration of tendon

What is tendinitis? How long does it take to heal and what are the treatments?

• Presence of acute inflammatory cells and proteins

  • Pain, swelling, redness, warmth

• Pathology of youth (<30 years)

  • Primarily affects younger people

• Pain with resisted mm. Testing for young patients indicates tendinitis - NOT tendinosis

• Should resolve w/in 6 weeks

• Crepitus

  • Sticking of the tendon due to the accumulation of inflammatory by-products on irritated tissue

• Treatment = Rest

  • Eliminate repetitive motion causing irritation

  • Substitute activity to maintain fitness

What is Tendinosis? How long does it take to heal and what are the treatments??

• Gradual, progressive, degenerative changes affecting the tendon

• Increased apoptosis (process of programmed cell death)

• Low pro-inflammatory markers

  • Source of pain is unclear d/t lack of inflammation

• Tendon will be thick d/t poor tissue healing → can progress to partial tear

• Takes 3 months - 1 year to resolve, often with lots of recurrence

• Limited role for NSAIDs d/t no inflammation

  • NSAID = Non-steroidal anti-inflammatory drug

• Best managed through eccentric loading

  • Physiological effect at the cell level that allows for regeneration of the tendon/cellular turnover

What is the difference between Tendinitis and Tendinosis

Why is Tendinosis not an appropriate term in many cases, like Achilles Tendinopathy?

• Docking et al. in 2021 found that the prevalence of Achilles tendon abnormalities in people without symptoms ranged from 0 to 80% Study by Lieberthal et al. in 2019 concluded a high prevalence of tendon pathology (46%) in an asymptomatic male running population with no history of Achilles tendon pain

What is the simplified cause of Tendinopathy? What are the Goals in rehabbing it?

• Understanding and monitoring pain

• Load management and activity modifications

• Understand rehab stages

What is it important to ask yourself when monitoring pain?

Ask yourself:

• Is your pain tolerable during exercise?

  • try to keep it <5/10

• Is my pain better, worse or the same after exercise?

  • Tendinopathy is often subject to the warm-up effect, t/f pain feels better after exercise

• Is my pain better, worse or the same the day after exercise?

  • If you are significantly worse the next day, back off the intensity

What should you avoid when going through physical rehab? What should you instead focus on?

• Mistakes include doing too little (fear of pain) and doing too much (pushing through the pain)

• Instead, focus on function, not pain

  • Work towards a physical goal

What are the different stages of rehab?

• Stage 0 - Anyone can do this exercise with minimal symptoms

• Stage 1 - Heavy, slow exercise that biases eccentric activity

• Stage 2 - Plyometrics, explosive activity

• Stage 3 - Return to sport

What is Achilles tendinopathy? What are the treatments

• Definition: Achilles tendinopathy = persistent Achilles tendon pain and loss of function due to mechanical loading

• Not inflammation-driven - Ice and complete rest are not the main rehab strategies

• Not degeneration-focused - Interventions should not aim to change tendon structure

• Cause - Occurs when tendon loading exceeds recovery and adaptation capacity

• Rehab goal: Balance load and capacity so the tendon can tolerate daily and weekly demands. Avoid Boom-bust cycles

• Early strategy: Avoid too much too soon and find a goldilocks zone that keeps symptoms manageable

• Exercise program: Commit to at least 3+ months of progressive exercises to restore function and tolerance

• Adjunct treatments: Pain relief options can help, but should not be the main focus, especially if costly or risky

• Key to success: No quick fix, requires patience, consistency, and dedication to a structured plan

What are Myofascial Trigger points?

• Discrete and hypersensitive nodule within tight band of muscle or fascia

• Result of acute trauma or microtrauma

• Hypothesized that build up of ACh at neuromuscular junction or lack of ATP leads to the formation of taut band

• Can be treated with manual soft tissue techniques, foam rolling, dry needling

• Classified as latent or active

  • Latent = does not cause spontaneous pain but may restrict movement or cause muscle weakness → aware once pressure is applied

  • Active = causes pain at rest, elicits “jump sign” when pressure is applied, causes a referred pain pattern similar to the patient’s pain complaint

• Ischemia - Lack of blood flow

What are contusions? How long does it take to heal and what are the treatments?

• Result of sudden blow to the body

• AKA “bruise”

• MOI: Compression

• A hematoma results from blood flowing into the surrounding tissue

• Causes Ecchymosis

  • Bluish-purple discoloration of the skin

• Pain usually resolves w/in a few dats, discoloration disappears w/in a few weeks

• Avoid aggressive massage or repeated blows to an area d/t risk of Myositis Ossificans

  • Myositis ossificans - Bone tissue grows inside of the muscle

What are ligament sprains? What are the different grades? Can ligaments heal?

• Stretch or tear of ligament

• MOI: Tension or shear force

• Compromises the ability of the ligament to stabilize the joint

• Graded on a 3-point scale

• Grade 1

  • Mild - moderate pain

  • No laxity

  • Firm end-feel

  • Local swelling

• Grade 2

  • Mod - severe pain

  • Laxity

  • Firm end-feel

  • Trouble WBing

• Grade 3

  • Pain?

  • Laxity

  • No end-feel

  • Loss of function

• The greatest difficulty with grade one and two sprains is restoring stability due to stretched tissue and inelastic scar tissue formation

• To regain joint stability, strengthening of muscles around the joint is critical

  • Dynamic stability = stability created from muscles around the joint

What is joint subluxation/dislocation?

• Joint force beyond normal limits results in separation of bony articulating surfaces

• Dislocation:

  • Occurs when at least one bone in a joint is forced out of alignment and must be manually a or surgically reduced

• Subluxation:

  • Partial dislocation causing incompletes

  • Bines come back together in alignment

• Stabilizing structures of the joint are disrupted

• Joints often become susceptible to subsequent dislocations

• X-ray is the only absolute diagnostic technique

• Dislocations (particularly the first time) should always be considered and treated as a fracture until ruled out

  • Once a dislocation, always a dislocation

• Dislocations should only be reduced after thorough ax of sensory, motor, and vascular status

What is osteoarthritis? How is it managed

• Degeneration of hyaline cartilage

• Changes in joint mechanics lead to joint degeneration

• Commonly affects weight-bearing joints but can also impact the shoulders and cervical spine

• Pain (particularly in the morning), stiffness, creaking

• One of the leading causes of disability in population

• Physical activity is the highest level of evidence for managing arthritis currently

• GLA;D program for knee and hip arthritis (GLA;D = Good life with arthritis, Denmark

• TKA, THA if pt doesn’t respond to conservative therapy

• Recent evidence from Stanford shows blockage of a specific protein may allow for cartilage repair

  • Protein 15-PGDH increases with age → interferes with cartilage repair, contributing to OA

  • In mice, blocking the 15-PGDH led to thicker, healthier knee cartilage → prevented OA after joint injury

  • Cartilage regeneration occurred without stem cells → existing cartilage cells changed their activity to repair tissue

  • Treated mice move more normally and showed less pain, suggesting real functional improvement

  • Similar cartilage regeneration effecrs were seen in human knee tissue samples (post-TKA) showing potential for future OA Tx

What are Bone fractures? (MOI, Classifacation, signs & symptoms, treatments)

• MOI

  • Fracture may be direct (at point of force application) or indirect

• Classified as either closed or open

  • Closed = little movement or displacement, no disruption to skin

  • Open = displacement of the fractured ends and breaking through the tissue

• Signs and symptoms

  • Deformity

  • Pain

  • Point tenderness

  • Swelling

  • Pain with AROM & PROM

  • Xray necessary for diagnosis

• Treatment may require reduction if fx displaced

  • Closed reduction

    • Physician manipulates into correct postion

  • Open reduciton

    • Surgical pins or wires secure ends

• Immobilization of bone with cast required for healing

  • Time required depends on severity, bone that broke, age of patient

What are stress fractures? (MOI, signs and symptoms, most common sites, treatment)

• Sometimes called a hairline fx

• No specific cause but with a number of causes

  • Overload due to muscle contraction, altered stress, distribution due to muscle fatigue, changes in surface, and rhythmic repetitive stress vibrations, altered bone density

• Typical MOI

  • Coming back to competition too soon after injury

  • Changing events without proper conditioning

  • Starting initial training too quickly

  • Changing training habits (surfaces, shoes, etc)

• Signs and symptoms

  • Early stages: swelling, focal tenderness, pain with activity

  • Later stages: Pain becoming constant & more intense, particularly at night, positive percussion tap test at site away from suspected fx

• Most common sites - Tibia, fibula, metatarsal shaft, femur, pars interarticularis (l-sp vertebrae), ribs, humerus

• Since early detection is difficult, a bone scan is useful; xray is effective after several weeks

• Treatment is varied, but often rest 2-4 weeks so doesn’t progress to true fx

How is the blood and nerve supply for each of these tissues?

• Ligament

• Tendon

• Hyaline cartilage

• Fibrocartilage

• Muscle

• Bone

What are the three phases of the healing process?

1. inflammatory response

2. Proliferation/fibroblastic repair

3. Maturation/remodeling

What does the inflammatory response phase entail?

• Time course: immediately to 4 days post-injury

• Function: to start healing, stop the bleeding, and remove foreign material

• Chemical mediators & cells cause vascular and cellular changes

  • Initial vascular response is vasoconstriction to limit blood loss (5 -10 mins)

  • Platelets critical for formation of a clot to stop the bleeding

  • Histamine then causes vasocilation and increases cell permeability

    • Reults in swelling but brings neutrophils and macrophages to clean up area and remove cellular debris caused by injury

  • Prostaglandins sensitize pain receptors (hyperalgesia)

What are the cardinal signs of inflammation and why do they happen?

1. Red (Rubor)

2. Hot (Calor)

3. Swollen (Tumor)

4. Tender (Dolor)

5. Loss of function

• Local vasodilation and fluid leakage into extracellular spaces = redness, swelling, and increased tissue temperature

• Mechanical distention, resulting in pressure on soft tissue, coupled with chemical irritation of specific nerve receptors = pain

What happens in the Proliferation / Fibroblastic Repair phase?

• Time course: ~3-4 days post injury up to 4-6 weeks

• Function: Scar formation and repair of injured tissue

• Formation of granulation tissue

  • Angiogenesis (blood vessels)

  • Collagenous scar tissue → produced by fibroblasts

• Angiogenesis

  • Essential for scar formation

  • Need new capillaries for bringing fibroblasts, oxygen and nutrients

  • Chemical stimulus for angiogenesis from macrophages and platelets

• Fibroblasts appear 2-3 days after injury

  • Produce glycosaminoglycans (GAGs) and collagen (Both part of the extracellular matrix)

    • GAGs attract water

    • Collagen fibres fill in gaps in tissue between cells

  • Collagen production begins after 3 days

    • Initially type lll

    • Increase in collagen correlates with wound tensile strength

How does cellular response and vascular response work together towards healing?

What happens in the maturation/remodeling phase?

• Three weeks up to 3 years

• Function: to increase scar strength

• Continued breakdown and synthesis of collagen

  • Conversion of Type lll collagen to Type l collagen

  • Increased number of cross-links = increase in strength

  • Orientation of collagen fibers along direction of mechanical force

  • Tissue will gradually resume normal appearance

    • Though rarely returns to same tensile strength d/t scar

Gain a general understanding to how long each type of tissue takes to heal

What are the 4 stages of Bone repair? What is happen in each stage?

1. Hematoma formation

   • Clotted blood from torn blood vessels

2. Soft callus formation

   • Macrophages clear cellular debris

   • Collagen fibers connect broken ends to allow catilage to be laid down

3. Hard callus formation

   • Trabeculae are formed from cartilage, and lay down spongy bone

4. Bone remodeling

   • Spongy bone remodelled into compact bone and excess bony material is removed

What are the overall goals of physical rehab?

1. Reduce pain

2. Restore ROM

3. improve strength

What is the old method for acute injury treatments? What is the new method to acute injuries? How do they compare?

Old method

• RICE

  • Rest - to reduce risk of further injury or irritation

  • Ice - Relives pain and reduces internal and external bleeding

  • Compression - To reduce swelling

  • Elevation - Also helps to reduce internal bleeding and swelling

New method

PEACE & LOVE

• PEACE

  • Protect - limit movement for 1-3 days to reduce risk of further injury or irritation

  • Elevate - Raise injured limb above heart to reduce swelling buildup

  • Avoid anti-inflammatories - Can delay healing

  • Compression - Elastic bandage to support circulation, provides swelling control

  • Education - Learn about your injury and how to treat it

• LOVE

  • Loading - light, pain-free loading promotes blood flow and tissue healing

  • Optimism - Brain has a significant effect on prognosis and optimal recovery

  • Vascularization - light aerobic activity improves blood flow

  • Exercise - Restores mobility, strength and proprioception

What is the role of progressive mobilization?

• Initally must maintain some immobilization in order to allow for initial healing

• In proliferation phase, controlled activity should be added

  • Work toward regaining normal flexibility and strength

  • Protective bracing may also be incorporated

    • Facilitates tissue remodelling and realignment

  • Must be aware of pain and other chemical signs, may be too much too soon

What is pain defined as?

• An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

• Major indicator of injury

• Individual and subjective

  • Modified by past experiences and expectations

• Pain is an output, not an input

  • The result of the brain’s scrutiny of many inputs, including nociception, emotional state, context, past experiences, body region, cultural values, etc

What is Pain vs Nociception?

• Nociception

  • To receive information about harm or damage

• Nociception is but one input required for the output that we think of as pain

  • Nociception is neither necessary nor sufficient for pain experience

• Acute pain

  • Pain associated with tissue damage or the threat of such damage and typically resolves once the tissue heals or the threat resolves

• Chronic pain

  • Pain that lasts longer than 6 months and is in the absence of tissue damage

  • Pain that lasts longer than the tissue healing process

  • Arthritis doesn’t count; even though the pain might be chronic, there is an underlying issue

What are some sources of pain?

• Cutaneous pain

  • Sharp, bright, and burning; it can have a fast or slow onset

• Deep somatic pain

  • Originates in tendons, muscles, and joints, and blood vessels, often achy or throbbing

• Visceral pain

  • Begins in organs, and is diffuse at first and may later be localized

• Psychogenic pain

  • Felt by the individual but is emotional rather than physical

What are nociceptors?

• Free nerve endings

  • Located as distal ends of peripheral neurons

  • Respond to mechanical, thermal and chemical stimuli

  • Found in all tissues except the central nervous system

  • Nociceptors are triggered, and then the impulse travels to the brain to potentially produce pain

    • Transmitted to the spinal cord via A-delta fibres and C fibers

What is the nociceptive pathway? What are 1st, 2nd, and 3rd order neurons?

• 1st-order neuron synapses in the dorsal horn of SC

• 2nd-order neurons cross the midline and ascend SC

  • End in thalamus

• 3rd-order neurons travel to the somatosensory cortex

What is the gate control theory of pain?

• Published by Melzack and wall in 1965

• Explains how a stimulus that activates only non-nociceptive nerves can inhibit pain

• Sensory fibres that transmit normal sensation are going to travel on a different pathway, they don’t synapse on the second order neuron so they get to the brain faster

• Normal sensation has an excitatory signal to the inhibitory interneuron (exciting inhibition = inhibition of pain reception)

What is the theory of selective tissue tension testing (STT)? How is it used in practice?

• Systematic examination by testing the injured part with active, passive and resisted movements to determine if problem is contractile or inert to decide on appropriate treatment strategy

• Contractile structures

  • Muscle, tendon

  • Implicated when pain increases with active and resisted movement in the same direction, and passive movement (stretch) in the opposite direction

• Inert Structures

  • Ligament, fascia, nerve roots, joint capsules

  • Implicated when pain increases with stretch of the tissue but resisted movement is not painful