Tissue Characteristics & Healing

• Difference between acute and chronic:

  • acute = clear cause/initiation of an injury; can be sudden
  • chronic = when injuries don’t heal
• Injury classification:

  • traumatic = occur suddenly, clear cause
  • occurs when tissue loading is sufficient and causes irreversible deformation
  • usually in high speed sports
  • with or without contact
  • overuse injuries occur slowly over time; they are secondary to the repetitive movements of the sport or movement in question
  • repeated overloading when accumulated over time exceeds tissue threshold
  • no time for repair
  • seen in aerobic sports that require lengthy training
  • seen in technical sports that required repeated movements
• Muscle characteristics:

  • contractile tissue
  • generate power
  • vascularized
  • good O2 and nutrients
  • good for healing
  • bleed a lot
• Muscle tears…:

  • called strains
  • look for percent of fibres torn
  • look for an ability to move through a range
  • look for strength generated
  • look for pain
• Grading Muscle Strength:

  • grade 5 = normal; full strength
  • grade 4 = good; near full strength
  • grade 3 = fair; full range of motion against gravity
  • grade 2 = poor; full range of motion with gravity eliminated
  • grade 1 = trace; palpate muscle contraction but no movement
  • grade 0 = nothing happens
• Muscle injuries:

  • distension = strain/pulled muscle
  • direct trauma = contusion/laceration
• Muscle strains:

  • occur at the musculotendinous junction
  • common in 2 joint muscle
  • due to forcible stretching of a muscle (passively or when muscle is active)
  • therefore: active contraction + passive stretch = strain
• Grade 1 strain:

  • less than 20% of fibres
  • near full ROM
  • good strength (4-5/5)
  • slight pain
  • no palpable divot
• Grade 2 strain:

  • usually 20-80% of fibres torn
  • significant decrease in ROM
  • poor strength (2-3/5)
  • significant pain
  • can palpate a divot
• Grade 3 strain:

  • 80-100% fibres torn
  • PROM
  • variable pain
  • poor strength (0-1/5)
  • large gap/muscle retraction
• Muscle contusions:

  • quads most common
  • due to vascularity, ecchymosis are common
  • internal bleeding
  • intramuscular or intermuscular
• Intramuscular:

  • no injury to fascia
  • blood trapped in muscle
  • longer healing time
  • due to increased compartment pressure, decreased blood flow/O2/nutrients, chemical irritation
• Intermuscular:

  • fascia is injured
  • blood flows out between muscles
  • bruising appears faster
  • heals faster
  • due to no increased pressure, more blood flow, blood can be absorbed, no irritation
• Tendon characteristics:

  • connective tissue
  • connects muscle to bone
  • function is to transfer force
  • made of 65-80% type 1 collagen
  • arranged into parallel fibres
• Tendon injuries:

  • traumatic
  • overuse
• Tendinitis/paratenonitis:

  • tendinitis = inflammation of the tendon; it is rare
  • paratenonitis = inflammation, pain, crepitation of the paratenon as it slides over the structure
  • *** acute irritation
• Tendinopathy:

  • refers to pain and reduced function in tendons
  • acute or chronic
• Tendinosis:

  • if repetitive overuse continues and inflamed or irritated tendon fails to heal, tendon begins to degenerate.
  • chronic pathological changes due to repetitive micro-trauma.
  • inflammatory cells are absent.
  • changes in collagen fibre structure.
  • abnormal vascularity
• Collagen fibre changes:

  • collagen fibre in disarray
  • loss of parallel bundles
  • fewer cell nuclei
  • hyper vascularity
  • more poor quality blood vessels
  • poorly spaced
• Ligaments:

  • bone to bone
  • made from collagen and elastin.
  • passive stabilizers.
  • they are usually a traumatic mechanism of injury.
  • well innervated for position, movement, pain.
  • innervation for proprioceptive cues and rehabilitation
• Types of ligaments:

  • intra-articular = inside a joint/joint capsule; rupture will not heal; ACL
  • capsular = ligament projects as a thickening of a joint capsule; excellent healing; good blood supply; ATFL & MCL
  • extra-capsular = outside joint capsule; not well vascularized; does not heal well; CFL & LCL
• Properties of ligaments:

  • wave/crimp across the ligament
  • injury due to load-deformation curve (positive correlation)
  • 3 phases: toe, linear, rupture
• Toe region:

  • normal physiological range of strain = 0-2% of length
  • early linear region = 2-4% of length (flatting of crimp)
  • cycle is reversible
  • no damage
  • occurs within physiological limits
• Late linear region:

  • irreversible ligament elongation
  • cross-links are disrupted until macroscopic failure is evident
  • early part = mild/grade 1 —> less than 50%
  • second part = grade 2 —> 50-80% fibre disruption; clinical laxity
• Rupture region:

  • failure point at 10% remaining fibres
  • complete rupture
  • grade 3 sprain
  • variable pain
• Ligament tears:

  • sprains
  • look for % of fibres torn
  • look for ability to move through range
  • look for laxity
  • look for endpoint
  • look for pain
• Grade 1 sprain:

  • full ROM
  • slight pain
  • no joint laxity
  • good stability
  • endpoint
• Grade 2 sprain:

  • significant loss of motion
  • significant pain
  • significant joint laxity
  • endpoint
• Grade 3 sprain:

  • complete loss of motion
  • variable pain
  • gross laxity
  • no endpoint
• Tissue healing:

  • inflammatory phase
  • repair phase
  • remodelling phase
• Inflammatory phase:

  • lasts 3-4 days
  • cellular injury = altered metabolism and release of chemical mediators/proteins
  • these cause the inflammatory response
• Primary damage:

  • damage at the time of injury
  • irreversible
• Secondary damage:

  • damage by released proteins
  • damage due to body processes
  • edema
  • decreased blood flow
  • decreased O2
• Signs and symptoms of inflammation:

  • redness
  • swelling
  • pain
  • local heat
  • loss of function
• Sub cycle:

  • pain
  • spasm
  • ischemia
  • pain causes muscles to spasm, spasm causes decrease blood flow, decrease blood flow causes ischemia, ischemia causes potential atrophy, which causes pain
  • cycle continues
• Repair phase:

  • 72 hours to 6 weeks
  • proliferative and regeneration healing
  • leads to connective tissue formation
  • formation of a weak scar
  • repair of injured tissue
  • fibroplasia begins
  • inflammatory signs begin to decrease
  • growth of endothelial capillary buds, stimulated by lack of O2
  • new capillaries allow more O2 and blood flow
  • body lays down type 3 collagen
  • weak tensile strength
• Remodelling phase:

  • strong, non-vascular scar at the end of week 3
  • long term process can take 6 weeks to a year
  • increase stress and strain = collagen changes from type 3 to type 1
  • realignment begins
  • Wolf’s law = bone and soft tissue respond to physical demands placed on them, causing them to align along lines of tensile force
  • important that injured structures are exposed to progressively increasing loads
  • to facilitate remodelling and realignment
  • watch out for pain and swelling after exercise