 Tissue Properties  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 load can resist  Stress  Internal resistance to a load  Strain  Internal change in tissue (i.e. length) resulting in deformation

Figure 9-1

 Body tissues are viscoelastic and contain both viscous and elastic properties  Yield point  Point at which elasticity is almost exceeded is the yield point  If deformation persists, following release of load permanent or plastic changes result  When yield point is far exceeded mechanical failure occurs resulting in damage

 Tissue Loading  Tension  Force that pulls and stretches tissue  Compression  Force that results in tissue crush – two forces applied towards one another  Shearing  Force that moves across the parallel organization of tissue Figure 9-2

 Bending  Two force pairs act at opposite ends of a structure (4 points)  Three forces cause bending (3 points)  Already bowed structures encounter axial loading  Torsion  Loads caused by twisting in opposite directions from opposite ends  Shear stress encountered will be perpendicular and parallel to the loads Figure 9-2

Traumatic vs. Overuse Injuries  Nature of physical activity dictates that over time injury will occur  Debate over acute vs. chronic injuries  When injury is acute – something has initiated the injury process  Injury becomes chronic when it doesn’t properly heal  Could define relative to mechanism  Traumatic (i.e. a direct blow) vs. Overuse (i.e. repetitive dynamic use over time)

Musculotendinous Unit Injuries  High incidence in athletics  Anatomical Characteristics  Composed of contractile cells that produce movement  Possess following characteristics  Irritability  Contractility  Conductivity  Elasticity

 Muscle Strains  Stretch, tear or rip to muscle or adjacent tissue  Cause is often obscure  Abnormal muscle contraction is the result of 1)failure in reciprocal coordination of agonist and antagonist, 2) electrolyte imbalance due to profuse sweating or 3) strength imbalance  May range from minute separation of connective tissue to complete tendinous avulsion or muscle rupture

 Muscle Strain Grades  Grade I - some fibers have been stretched or actually torn resulting in tenderness and pain on active ROM, movement painful but full range present  Grade II - number of fibers have been torn and active contraction is painful, usually a depression or divot is palpable, some swelling and discoloration result  Grade III- Complete rupture of muscle or musculotendinous junction, significant impairment, with initially a great deal of pain that diminishes due to nerve damage  Pathologically, strain is very similar to contusion or sprain with capillary or blood vessel hemorrhage

 Muscle Cramps  Painful involuntary skeletal muscle contraction  Occurs in well-developed individuals when muscle is in shortened position  Experienced at night or at rest  Muscle Guarding  Following injury, muscles within an effected area contract to splint the area in an effort to minimize pain through limitation of motion  Involuntary muscle contraction in response to pain following injury  Not spasm which would indicate increased tone due to upper motor neuron lesion in the brain

 Muscle Spasms  A reflex reaction caused by trauma  Two types  Clonic - alternating involuntary muscular contractions and relaxations in quick succession  Tonic - rigid contraction that lasts a period of time  May lead to muscle or tendon injuries

 Muscle Soreness  Overexertion in strenuous exercise resulting in muscular pain  Generally occurs following participation in activity that individual is unaccustomed  Two types of soreness 1) Acute-onset muscle soreness - accompanies fatigue, and is transient muscle pain experienced immediately after exercise 2) Delayed-onset muscle soreness (DOMS) - pain that occurs hours following activity that gradually subsides (pain free 3-4 days later)  Potentially caused by slight microtrauma to muscle or connective tissue structures  Prevent soreness through gradual build-up of intensity

 Repetitive stress on tendon will result in microtrauma and elongation, causing fibroblasts influx and increased collagen production  Repeated microtrauma may evolve into chronic muscle strain due to reabsorption of collagen fibers  Results in weakening tendons  Collagen reabsorption occurs in early period of sports conditioning and immobilization making tissue susceptibility to injury – requires gradual loading and conditioning

 Tendinitis  Gradual onset, with diffuse tenderness due to repeated microtrauma and degenerative changes  Obvious signs of swelling and pain  Key to treatment is rest  May require substitution of activity in order to maintain fitness without stressing injured structure  Without proper healing condition may begin to degenerate and be referred to as tendinosis  Less inflammation, more visibly swollen with stiffness and restricted motion  Treatment involves stretching and strengthening  Becomes “osis” after ~6weeks Figure 9-5

 Tenosynovitis  Inflammation of synovial sheath  In acute case - rapid onset, crepitus, and diffuse swelling  Chronic cases result in thickening of tendon with pain and crepitus  Often occurs in long flexor tendon of the digits and the biceps tendon

 Myofascial Trigger Points  Discrete, hypersensitive nodule within tight band of muscle or fascia  Classified as latent or active  Develop as the result of mechanical stress  Either acute trauma or microtrauma  May lead to development of stress on muscle fiber = formation of trigger points  Latent trigger point  Does not cause spontaneous pain  May restrict movement or cause muscle weakness  Become aware of presence when pressure is applied

 Active trigger point  Causes pain at rest  Applying pressure = pain = jump sign  Tender to palpation with referred pain  Tender point vs. trigger point  Found most commonly in muscles involved in postural support

 Contusions  Result of sudden blow to body  Can be both deep and superficial  Hematoma results from blood and lymph flow into surrounding tissue  Localization of extravasated blood into clot, encapsulated by connective tissue  Speed of healing dependent on the extent of damage  Chronically inflamed and contused tissue may result in generation of calcium deposits (myositis ossificans)  Prevention through protection of contused area with padding

 Atrophy and Contracture  Atrophy is wasting away of muscle due to immobilization, inactivity, or loss of nerve functioning  Contracture is an abnormal shortening of muscle where there is a great deal of resistance to passive stretch  Generally the result of a muscle injury which impacts the joint, resulting in accumulation of scar tissue

Synovial Joints Injuries  Each joint has both hyaline or articular cartilage and a fibrous connective tissue capsule  Additional synovial joint characteristics  Capsule and ligaments for support  Capsule is lined with synovial membrane  Hyaline cartilage  Joint cavity with synovial fluid  Blood and nerve supply with muscles crossing joint  Menisci (fibrocartilage)

 Sprains  Result of traumatic joint twist that causes stretching or tearing of ligament  Graded based on the severity of injury  Grade I - some pain, minimal loss of function, no abnormal motion, and mild point tenderness  Grade II - pain, moderate loss of function, swelling, and instability with tearing and separation of ligament fibers  Grade III - extremely painful, inevitable loss of function, severe instability and swelling, and may also represent subluxation

 Can result in joint effusion and swelling, local temperature increase, pain and point tenderness, ecchymosis (change in skin color) and possibly an avulsion fracture  Greatest difficulty with grade 1 & 2 sprains is restoring stability due to stretched tissue and inelastic scar tissue which forms  To regain joint stability strengthening of muscles around the joint is critical

 Dislocations and Subluxations  Result in separation of bony articulating surfaces  Subluxation  Partial dislocations causing incomplete separation of two bones  Bones come back together in alignment  Dislocations  High level of incidence in fingers and shoulder  Occurs when at least one bone in a joint is forced out of alignment and must be manually or surgically reduced  Gross deformity is typically apparent with bilateral comparison revealing asymmetry

 Dislocation (cont.)  Stabilizing structures of the joint are disrupted  Joint often becomes susceptible to subsequent dislocations  X-ray is the only absolute diagnostic technique (able to see bone fragments from possible avulsion fractures, disruption of growth plates or connective tissue)  Dislocations (particularly first time) should always be considered and treated as a fracture until ruled out  “Once a dislocation, always a dislocation” Figure 9-9

 Osteoarthritis  Wearing away of hyaline cartilage as a result of normal use  Changes in joint mechanics lead to joint degeneration  Commonly affects weight bearing joints but can also impact shoulders and cervical spine  Symptoms include pain (as the result of friction), stiffness, prominent morning pain, localized tenderness, creaking, grating  Either generalized joint pain or localized to one side of the joint Figure 9-10

 Bursitis  Bursa are fluid filled sacs that develop in areas of friction  Sudden irritation can cause acute bursitis, while overuse and constant external compression can cause chronic bursitis  Signs and symptoms include swelling, pain, and some loss of function  Repeated trauma can lead to calcification and degeneration of internal bursa linings Figure 9-11

 Capsulitis and Synovitis  Capsulitis is the result of repeated joint trauma  Synovitis can occur acutely but will also develop following mistreatment of joint injury  Chronic synovitis can result in edema, thickening of the synovial lining, exudation can occur and a fibrous underlying develops  Motion may become restricted and joint noises may develop

 Bone Fractures  Classified as either closed or open  Closed fractures are those where there is little movement or displacement  Open fractures involve displacement of the fractured ends and breaking through the surrounding tissue  Serious condition if not managed properly  Signs & symptoms  Deformity, pain, point tenderness, swelling, pain on active and passive movements  Possible crepitus  X-ray will be necessary for definitive diagnosis

 Mechanism of Injury  Fracture may be direct (at point of force application) or indirect  Sudden violent and forceful muscle contraction  Types of fractures  Greenstick  Comminuted  Linear  Transverse  Oblique  Spiral  Impacted Figure 9-13

 Types (cont.)  Avulsion  Separation of bone fragment from cortex via pull of ligament or tendon  Blowout fracture  Serrated fracture  Depressed fracture  Contrecoup fracture

 Bone Strength & Shape  Strength of bone can be impacted by changes in shape and direction  Long bones with gradual changes are less prone to injury  Cylindrical and hollow nature of bones make them very strong - resistant to bending and twisting  Bone Loading Characteristics  Bones can be stressed or loaded to failure by tension, compression, bending, twisting and shearing

 Long Bone Load Characteristics (cont.)  Either occur singularly or in combination  Amount of load also impacts the nature of the fracture  More force results in a more complex fracture  While force goes into fracturing the bone, some energy and force is also absorbed by adjacent soft tissues  Bone has elastic properties allowing it to bend  Typically brittle and a poor shock absorber  Brittleness increases under tension force s, more so than under compression

 Stress fractures  No specific cause but with a number of possible causes  Overload due to muscle contraction, altered stress distribution due to muscle fatigue, changes in surface, rhythmic repetitive stress vibrations  Bone becomes susceptible early in training due to increased muscular forces and initial remodeling and resorption of bone  Progression involves, focal microfractures, periosteal or endosteal response (stress fx) linear fractures and displaced fractures  Early detection is difficult, bone scan is useful, x- ray is effective after several weeks

 Typical causes include  Coming back to competition too soon after injury  Changing events without proper conditioning  Starting initial training too quickly  Changing training habits (surfaces, shoes….etc)  Variety of postural and foot conditions  Signs and symptoms  Focal tenderness and pain, (early stages)  Pain with activity, (later stages) with pain becoming constant and more intense, particularly at night, (exhibit a positive percussion tap test)  Common sites involve tibia, fibula, metatarsal shaft, calcaneus, femur, pars interarticularis, ribs, and humerus  Management varies between individuals, injury site and extent of injury

 Epiphyseal Conditions  Occur most often in children ages years old  Classified by Salter-Harris into five types  Apophyseal Injuries  Young physically active individuals are susceptible  Apophyses are traction epiphyses in contrast to pressure epiphyses.  Serve as sites of origin and insertion for muscles  Common avulsion conditions include Sever’s disease and Osgood-Schlatter’s disease

 Osteochondrosis  Also known as osteochondritis dissecans and apophysitis (if located at a tubercle/tuberosity)  Causes not well understood  Degenerative changes to epiphyses of bone during rapid child growth  Possible cause includes 1)aseptic necrosis (disrupted circulation to epiphysis, 2) fractures in cartilage causing fissures to subchondral bone, 3) trauma to a joint that results in cartilage fragmentation resulting in swelling, pain and locking  With the apophysis, an avulsion fracture may be involved, including pain, swelling and disability

Nerve Trauma  Abnormal nerve responses can be attributed to injury or athletic participation  The most frequent injury is neuropraxia produced by direct trauma  Lacerations of nerves as well as compression of nerves as a result of fractures and dislocations can impact nerve function

 Nerve Injuries  Compression and tension are primary mechanisms  May be acute or chronic  Physical trauma causes pain and can result in a host of sensory responses (pinch, burn, tingle, muscle weakness, radiating pain)  Long term problems can go from minor nerve problems to paralysis  Pain can be referred as well

 Neuropraxia  Interruption in conduction through nerve fiber  Brought about via compression, or tension  Impact motor more than sensory function  Temporary loss of function (sec.-> minutes)  Axonotmesis  More severe disruption of the axon but surrounding tissue remains in tact  Impacts motor and sensory  Minutes -> days  Neurotmesis  Complete disruption of the nerve  Days -> years (if at all)