PT661 exam 2

what is the verbage to describe knee angle of joint angular velocity?

• extending: moving towards extended position

• flexing: moving towards max flexion

what are the typical angles for knee ROM?

• 130-150 flexion

• 5-10 extension

what is the joint angle?

relative orientation of distal segment to the proximal segment in the sagittal plane

what is the shape of the knee joint?

a modified, four-bar linkage

• roll and slide possible with this shape

• functions for high stability and clearance during walking

• allows for more movement with roll + slide

where is the axis of rotation in the knee during flexion/extension?

• lines up with the femoral condyles

• in different positions, the axis of rotation changes

• instantaneous center/axis of rotation

femur movements in closed chain extending (tibia fixed)

femoral condyles

• roll anteriorly

• slide posteriorly

tibia movements in open chain extending (femur fixed)

tibial plateaus

• roll anteriorly

• slide anteriorly

femur movements in closed chain flexing

femoral condyles

• roll posteriorly

• slide anteriorly

tibia movements in open chain flexing

tibial plateaus

• roll posteriorly

• slide posteriorly

what is the close-packed position?

when you have the most stability

• maximal bony congruence and ligaments are taut

• provides natural stability

what is the screw home mechanism?

full (maximal) knee extension coupled with knee external rotation (last 20 degrees)

• provides maximum stability

• reduced muscular effort during standing

what is the loose-packed posiiton?

about mid range (about 25 degrees of flexion)

• minimal bony congruence

• ligaments are lax

• minimal intra-articular pressure

what is adduction (varus) or abduction (valgus) position of the knee

relative orientation of distal segment to the proximal segment in the frontal plane

• abducted/in abduction/valgus

• adducted/in adduction/varus

in acting adduction/abduction movement

• adducting

• abducting

what is normal range for knee valgus/varus

about 170-175 degrees valgus

• males usually have a greater angle (narrower pelvis)

what is the range of motion for valgus/varus movement?

• 8 degrees in extension

• 13 in 20 degrees of flexion

are untypical alignment of the knee

not always an issue if asymptomatic

• not always predictive of injuries or performance

• will change distribution of forces in the limb

what is the load bearing axis?

where the force passes through

• femoral head (hip center) to knee center

• knee center to ankle center

• alignment = no external moment arm

load bearing axis in genu varum

• external varus moment (forces pushing limb laterally)

load bearing axis in genu valgus

• external valgus moment (forces push limb medially)

how can internal valgus moments be reduced?

surgical

• total knee arthroscopy

• high tibial osteonomy

• distal femoral osteotomy

conservative

• lateral wedging

• valgus bracing

• gait modification

what is in internal/external rotation of the knee

relative orientation of distal segment to the proximal segment in the transverse plane

what is the typical range of motion for internal/external rotation?

minimal rotation with extended knee (close packed position, screw home)

• in knee flexion: 40-45 degrees total of rotation (external:internal, 2:1)

why does the screw home mechanism take place?

• lateral pull of the quadriceps (external rotation of the tibia)

• tension in ACL (pulls external rotation)

• shape of the medial condyles (medial is much larger + curved)

how is the knee “unlocked” from the screw home mechanism?

popliteus

• internally rotates the tibia (relative to femur)

what are the functions of the meniscus

• compressive load management (increases area of force absorption)

• joint stabilization

• lubrication

• proprioception

• guiding knee arthrokinematics

menisci mobility

• medial is more restricted to more ligamentous and capsular restrains

• in weight bearing positions, the meniscus moves more

knee flexion

• deform and slide posteriorly

knee extension:

• deform and slide anteriorly

what are responsible for menisci posterior glide?

semimembranosus and popliteus

what is the most common mechanism of injury for the menisci

• 50% of ACL injuries also with meniscus

• twisting/pivoted on loaded limb

• more common to medial meniscus

what is the vascularity/blood supply to the meniscus

• outer 3rd receives blood supply (red zone)

• inner zones require cyclic motion to pump nutrients

what are the implications of a torn meniscus

increase in contact pressure

• decreased area → increased stress

what are treatment options for menisci injuries

• partial meniscectomy: quicker return due to removal

  • but can have long term complications (arthritis)

• meniscus repairs: similar rates of return and level

rehabilitation principles following meniscus repairs

size, type, location of tear/repair

tests:

• knee joint ROM

• quadriceps and hamstring strength (stabilize meniscus)

• functional tests/movement performance and tolerance

what is the function of articular cartilage?

• decrease friction

• assist with shock absorption

• resist wear

how do the articular cartilage react to load during weight bearing

deforms 22-30%

• single support:

  • medial bears greatest (2.25 x BW)

  • lateral: 0.91 x BW

what are articular cartilage injuries

focal

• traumatic in origin

• focused site of injury

degenerative (OA)

• repetitive movements/aging

• peripheral tissues affected

role of cruciate ligaments

stabilizes against horizontal translation/shear loads

in the ACL, what are the two bundles of fibers

anteromedial bundle

• smaller

• tighter with greater knee flexion

posterolateral bundle

• tighter with greater knee extension

what are the two major functions of the ACL?

resist anterior translation and hyperextension

• anterior translation: hamstring can help

• hyperextension: hamstring does not help

what are the ACLs secondary restraints?

• can resist tibial internal rotation

  • due to tibial/femur attachments

• external valgus/varus forces (small influence)

ACL strain vs joint position

• max excursion at 30 degrees (loose-packed)

• anterior tibial translation = 5-8mm

where is the failure point of the ACL? and real life exercise ACL strain?

failure: 10%

strain in real life

• seated leg extension: -2.5% to 3.8%

  • -2.5% = the weight is helping the ACL keep the tibia not anteriorly displaced

• single leg squatL 3.2%

ACL injury

most frequent ligament rupture in the knee

• 50% in active ppl 15-25yrs

• 70% through non-contact ACL injuries

what is the ACL injury mechanism/when it is most loaded

• high GRF

• quad activation

• full extension

sex-based anatomical differences of the ACL

• decreased femoral notch width in females (more likely to bend and get caught)

• increased tibial slope (greater slope = larger component of force is anterior)

• increased knee laxity

sex-based biomechanical differences of ACL

• more extended hip and knee landing (females)

• greater knee valgus angles and moments

• poorer trunk control

what are the two bands of the PCL?

anterolateral

• tight in flexion

posteromedial

• taut in extension

PCL function and ROM

• resist posterior tibial translation

• taut in full flexion: 75-90 degree

• resistance to posterior translation from >30 deg flexion

• resist external rotation

• resist varus and valgus

layers of the medial collateral ligament

separated by bursa

superficial

• medal femoral epicondyle → medial proximal tibia

deep

• continuous with joint capsule

• medial femoral epicondyle → medial tibial plateau

when is the MCL taut?

full knee extension

• requires a lot of force until failure (800N)

function of the MCL?

• resist external valgus moment

• resist hyperextension

• resist rotation

• resist tibial anterior translation

when is the MCL providing the most stability?

flexion: 78% of valgus moment resisted

extension: 57% of valgus moment resisted (more capsule help)

what is the function of the medial capsule

stabailizing against external valgus forces

• reinforced with fascia, medial patellar retinacular fibers, MCL fibers, tendons

what is the LCL?

attaches to the proximal femoral condyle → fibular head

• only 400N of force to failure

• extracapsular

what is the function of the LCL?

• resist external varus moment/force

• resist hyperextension

• resist rotation

what is the function of the IT band?

• anterolateral support to the knee

• changes in angle change IT line of action

what are the levels of assistance?

• independent

• modified independent (MOD I)

• supervision (S)

• minimal assistance (MIN A)

• moderate assistance (MOD A)

• maximum assistance (MAX A)

what is the independent level of assistance?

no physical assistance or cuing required. performs tasks safely without an assistive device or modification.

what is the modified independent (MOD I) level of assistance?

physical assistance not required BUT

• may need assistive device/aide

• may need an increased amount of time

• may have safety concerns/risk considerations

what is the supervision (set-up or stand-by) level of assistance?

patient requires coaxing, cuing, and/or setup for successful and safe performance

• no physical touch

what is the minimal assistance (MIN A) level of assistance?

hands on assistance where the patient is able to perform 75-99% of the work

what is the moderate assistance level of assistance?

patient requires more physical assistance. patient is able to perform 50-75% of work

what is the maximal assistance level of assistance?

therapist provides over 50% of work

what are indications for assistive devices?

• decreased ability to bear weight on an extremity

• decreased trunk and/or lower extremity strength

• impaired balance

• impaired kinesthetic awareness

• to off-set LE pain

what are the weight bearing statuses?

• FWB

• Weight bearing as tolerated (WBAT)

• non weight bearing (NWB)

• partial weight bearing (PWB)

• heel weight bearing (HWB)

• toe touch weight bearing (TTWB)

what is weight bearing as tolerated?

patient can put as much weight on their lower extremities as they can tolerate

• usually needs assistive device due to pain and/or weakness

what is non-weight bearing?

limb does not touch ground or weight bearing surface

what is partial weight bearing?

the patient can put some but not all of their weight on an extremity often defined by a percentage

what is heel weight bearing?

patient can maintain contact of their heel only while in standing

• sometimes requires special surgical shoes

what is toe touch weight bearing?

no weight bearing through leg, but big toe on ground

• helpful input for balance

princpals of guarding

• maintain 2 points of contact to help maintain control over patient’s center of mass

• one posterior and one anterior point of contact

• in the presence of unilateral L impairment, guard on affected side

• loads are best managed when kept close to your body

• maintain a wide base of support, and stand close to patient

considerations for determining the best device for a patient

• support: mobile or stable

• impairment/deficit being compensated: strength, altered weight bearing status, balance

• benefits of device: mobile vs stable, restoration of normal gait pattern, assist with impairment?

• potential device limitations: safety (understanding + environment) considerations, gate mechanics

• environmental considerations: stairs, small spaces, community?

inherited collagen disorders

• marfan syndrome

• ehlers-danlos syndrome

autoimmune collagen disorders

• systemic lupus erythematosis

• scleroderma

• Sjorgen’s syndrome

• Polymyositis and Dermatomyositis

attributes of marfan syndrome

inherited, autosomal dominant disorder resulting in systemic weakening of the connective tissue

• Presentation: tall, disproportionately long arms and fingers, scoliosis, and pectum excavatum

• signs and symptoms: cardiac disease → aortic dissection or aneurysm

how should physical therapists treat individuals with marfan syndrome?

• avoid physical exertion

• maintain HR around 100-110 bpm

• nonstrenuous aroebic exercise

• noncompetitive

• isokinetic (NO ISOMETRICS)

• avoid sudden stops, rapid direction changes and contact

characteristics of Ehlers-Danlos Syndrome

inherited mutation in collagen

• presentation: multiple types spanning different systems, hypermobile joints, hyperextensible skin

• signs and symptoms: joint hypermobility, chronic dislocation, arthritis, musculoskeletal pain

how should physical therapists treat ehlers danlos syndrome

• joint protection

• strengthening

• joint ROM (physiologic range) + stability

• joint control

• posture improvement

what are the characteristics of lupus (mostly SLE)?

multiple types, autoimmune disorder

• most common: SLE - effects every organ system

• pathophys: inflammation in every organ system

• presentation: butterfly rash on cheeks, periods of inflammation and dormancy, joint swelling, mood changes,

• signs and symptoms: joint swelling and pain, pleural inflammation, kidney inflammation/disease, seizures

how would a physical therapist treat lupus?

• aerboic activity improves outcomes

• strength training

  • during periods of inflammation: isometrics

  • during periods of dormancy: isotonic

  • improve ROM and functional mobility

what are the characteristics of scleroderma

• pathophys: autoimmune disorder of increased collagen disposition leading to diffuse fibrosis

• presentation: tight, leathery, red skin (limited disease and diffuse disease)

• signs and symptoms: tight, leathery skin, calcium depositis, esophageal disfunction (decreased motility), dilation of capillaries = red dots,

  • diffuse

    • raynauds, GERD, difficulty swallowing, heart failure, kidney failure, pulmonary fibrosis

how do physical therapists treat scleroderma?

paraffin wax and heat

• increase superficial blood flow

• reduce pain and inflammation

• increase extensibility of tissues

ROM

• moth and hands

massage

aerobic and resistance training

what are the characteritics of Sjogrens syndrome?

• autosomal dysfunction of lacrimal and salivary glands

• could maybe do PT for some deconditioning

• most important to know because it is typically comorbid with other autoimmune disorders

what are the characteristics of polymyositis and dermatomyositis?

• pathophys: autoimmune inflammation of muscle fibers

• presentation: red skin rashes and muscle weakness

• signs and symptoms: rash on hands, around neck and chest (shawl), and around eyes, proximal muscle weakness

how would physical therapists treat polymyositis and dermatomyositis?

• maintain function and reduce fall risk

• exercise proximal muscles to increase strength

• combination of resistance and aerobic

what structures stabilize the patella?

• quadriceps tendon

• patellar tendon

• quadriceps muscles

• IT band

• retinacular fibers

how does the patella change knee extensor moment arms?

• in moves the muscle further from the point of rotation, creating a larger moment arm and therefore requiring less force to produce movement

where does the patella have the most contact with the femur in the ROM?

60-90 degrees of flexion

where does the patella have the most contact with the femur? what movement? why is this important?

• 60-90 degrees of knee flexion

• largest area on the femur (most of the trochlear groove and a largest portion of patella in contact

• good to know when there is less stress on the structures, due to forces being dispersed over a large area

when the leg is extended, where is the patella?

the is superior

• does not fit well into the trochlear groove

• mobile and susceptible to dislocations (where chronic dislocations occur)

• patella stability can be improved by active tension

what ways can the patellofemoral joint move (maladaptive)?

• lateral/medial glide

• medial/lateral tilt

• medial/lateral rotation (rotating in the frontal plane)

how does the line of action of the quadriceps muscles impact patella movement?

• rectus femoris and vastus intermedius pull patella proximally

• vastus lateralis: pulls patella up and laterally

• vastus medialis: pulls patella up and slightly medially, posterior (less pull than VL because its smaller)

Net action: superior, posterior, and lateral

how does the gastrocnemius contribute to secondary knee flexion?

• it crosses the knee joint at its origin

• originates on the femoral epicondyles

what is the function of the muscles in the pes anserine

medial stability and flexor moments

• typically harvested for ligament repairs in knee (like ACL)

how is patellar tracking quantified? typical range?

Quadriceps Q-angle

1. patella mid point → ASIS

2. patellas long axis

typical range: 13-15 degrees

• valgus increases angle

what are the net local factors contributing to patella movement

lateral directed:

• IT band tension

• bowstring force on patella (from quadriceps pulling)

• lateral patellar retinacular fibers

medial directed force

• vastus medialis (oblique)

• raised lateral facet of trochlear groove

• medial patellar retinacular fibers

what are the global factors impacting patellar forces? what can cause these?

how can the alignment impact

• odd lower limb configuration (knee external rotation and valgus)

  • creates a larger bowstring force on patella

• could originate from hip or ankle

• could originate from motor control problems: unawareness/no control of positioning

what is patellofemoral pain syndrome?

one of most common knee pains

• usually overuse in young and active individuals

• unaddressed: could develop osteoarthritis later in life

what are the biomechanics of patellofemoral pain syndrome?

• lateral pulling of patella

• positioning of lower limb

• patella contact force

what positioning generates the highest patellofemoral contact force?

a deep squat

• greater posterior forces pushing patella into femur at the same amount of muscle activation