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Terms in this set (71)
Functions of the knee joint
Shortens and lengthens the limb
Transmits force through the LE
Provides stability in weight bearing
Allows direction change when walking/running (rotation)
What type of joint is the tibiofemoral joint?
Modified hinge joint: does flexion/extension and rotation
What type of joint is the patellofemoral joint?
Plane joint (sliding motion)
Tibiofemoral Joint- open/close packed positions and capsular pattern?
Close packed (position of max joint surface congruency): 0* knee extension (lat rotation)
Open packed (position of max joint laxity): 25* knee flexion
Capsular pattern: flexion loss > extension loss
Where does tibiofemoral joint stability come from?
Minimal bony stability (relatively flat surfaces contacting each other)
Soft tissue stability: joint capsule, ligaments, cartilage, muscles, retinacular fibers
Motions limited by ACL?
Anterior translation of tibia
Full knee extension
Varus, valgus, extreme rotation
Motions limited by PCL?
Posterior translation of tibia
Full knee flexion
Varus, valgus, rotation, extreme extension
Motions limited by MCL/TCL?
Motions limited by LCL/FCL?
List the ligaments of the knee joint
Osteology of Femur
large condyles with intercondylar notch
Osteology of tibia
Transfers weight across knee through tibial plateuas
Medial tibial plateau: larger, concave
Lateral tibial plateau: smaller, flatter
Osteology of fibula
No direct function at knee joint
Supports lateral tibia
Attaches ligaments and muscles
Osteology of patella
Large sesamoid bone in quadriceps tendon
Curved wide base superiorly and pointed apex inferiorly
Posterior (articular) surface
3 facets: lateral, medial, odd
What structures provide anterior/posterior stability to the knee joint?
Ligaments: primary (cruciates: ACL, PCL), secondary (collaterals: MCL, LCL)
Muscles: quadriceps, hamstrings, gastroc, popliteus
Anterior Cruciate Ligament
2 bundles (ant/med and post/lat)
Most mechanoreceptors of the ligs in the knee (detect tension, send message to brain, brain fires quads and hamstrings to support knee)
Most injured ligament
Increased tension in full extension with valgus stress or rotation
Quad contraction at low flexion angles increases stress
Co-contraction with hamstrings helps decrease stress
Posterior Cruciate Ligament
2 bundles: ant/lat and post/med
Less injured and less stability issues when disrupted
Increased tension in flexion above 90*
Hamstring contraction increases stress
Co-contraction with quads decreases stress
ACL injury mechanism
Excessive anterior displacement of tibia on femur
Forceful hyperextension or extreme rotation (plant and twist) with valgus stress
PCL injury mechanism
Excessive posterior displacement of tibia on femur
Dashboard injury, falling with knee in full extension
What structures provide medial/lateral stability to knee joint?
Ligaments: primary (collaterals: MCL, LCL), secondary (cruciates: ACL, PCL)
Muscles: medial (sartorius, semitendinosus, semimembranosus, gracilis), lateral (iliotibial band, biceps femoris tendon, popliteus)
Medial Collateral Ligament
Main stabilizer against valgus stress
More taut in extension
Superficial and deep fibers- superficial (increased chance of injury with ER and valgus), deep (shorter and injured more frequently with pure valgus stress- attaches to medial meniscus and semimem. tendon, often injured together)
Lateral Collateral Ligament
Main stabilizer against varus stress
More taut in extension
No meniscal attachment (isolated LCL injury is common)
Lesion in MCL
excessive valgus displacement of tibia on femur
Lesion in LCL
excessive varus dispalcement of tibia on femur
What muscles attach to the menisci?
Quads and semimembranosus attach to both menisci
Popliteus attached to lateral meniscus
Blood supply/innervation of the menisci?
Internal portion- avascular (healing problems)
Aneural except near ant/post horns (no pain with injury)
Which meniscus is more susceptible to injury?
medial meniscus- bigger, attached to more things
What are the functions of the menisci?
Increase joint congruency (secondary stability, distribution of weight bearing forces)
Shock absorption (circumferential tension)
Triples contact area at knee joint
What are the 5 regions of the knee joint capsule?
Reinforced by oblique popliteal lig and arcuate popliteal lig
Reinforced by posterior musculature
Taut in full extension
Reinforced by arcuate popliteal lig and popliteus muscle & tendon
With damage, causes post/lat rotational instability
Posterior portion is thick and reinforced by pes anserine
Important for overall knee stability
Attaches to edge of patella, reinforced by quadriceps and retinacular fibers
Reinforced by LCL, lateral patellar retinacular fibers and ITB
Normal frontal plane alignment?
5-10* genu valgus
Children born bow-legged because o their position in utero, bones change as they grow over times
Greater than or equal to 15*
Structures on tension: MCL
Structures Compressed: lateral joint compartment
Less than or equal to 0* genu valgus
On tension: LCL
Compressed: medial joint compartment
Caused by growth plate injury/infection/malformation
Varus alignment increases likelihood of medial joint arthritis
Varus alignment associated with?
Increased risk of medial compartment OA progression
Decreased risk of lateral compartment OA progression
Valgus alignment associated with?
Increased risk of lateral compartment OA
Decreased risk of medial compartment OA
Normal sagittal plane alignment?
Normal hyperextension: 5-10*
Line of gravity from body weight anterior to knee joint (lets us avoid using quads, puts a little stress on posterior capsule)
What is genu recurvatum?
Knee hyperextension > 10*
Causes: weak quadriceps, laxity of posterior structures
Normal alignment in transverse plane?
Normal: tibial and femoral condyles aligned
Tibial rotation- structural or functional?
Tibial lateral rotation
Muscles: short ITB/TFL, biceps femoris; long semimembranosus, semitendinosus, sartorius, gracilis
Hip/femoral alignment: femoral anteversion
Tibial medial rotation
Muscles: short semimembranosus, semitendinosus, sartorius, gracilis; long ITB/TFL, biceps femoris
Hip/femoral alignment: femoral retroversion
Tibial torsion- structural or functional?
What is tibial torsion?
When the distal end of tibia twisted about long axis relative to proximal end
Normal: 20* lateral
Foot should appear slightly laterally rotated (10*) in standing
What alignment impairments could contribute to excessive toe out?
External tibial rotation at tibiofemoral joint
External tibial torsion
What alignment impairments could contribute to excessive toe in?
Internal tibial rotation at tibiofemoral joint
Internal tibial torsion
Normal patellofemoral joint alignment?
Superior/inferior (1:1 alignment with knee at 60* flexion between patella height and distance, and between inf pole of patella and tibial tuberosity)
Medial/lateral (normal is central to slightly lateral)
Tilt (slight lateral tilt with knee extended)
What is Q-Angle? Normal and atypical values?
Where quadriceps is pulling the patella
Normal values: men <10
, female <15
Atypical >15* (creates excessive lateral forces on patella, bowstring effect)
Associated with coxa vara/genu valgus and coxa valga/genu varum
2 degrees of freedom (flex/ext: med/lat axis; rotation (screw home mechanism): sup/inf axis)
Shape: convex femoral condyles; concave tibia and menisci
Knee extension ROM, arthrokinematics, muscles, menisci
ROM: 10* hyperextension
Arthrokinematics: open chain (anterior roll, anterior glide); closed chain (anterior roll, posterior glide)
Muscles: quads, minimal TFL via ITB
Menisci: pulled anteriorly by quads
Knee flexion ROM, arthrokinematics, muscles, menisci
Arthrokinematics: open chain (posterior roll and glide); closed chain (posterior roll, anterior glide)
Muscles: hamstrings, gastroc, popliteus, gracilis, sartorius, plantaris
Menisci: pulled posterior by hamstrings (semimem)
Patient with limited knee flexion. Treatment goal: to improve arthrokinematics of flexion. Recommendation?
Posterior glide of tibia on femur
anterior glide of femur on tibia
of conjunct tibial lateral rotation in the last 30
of knee extension
Allows standing without quad contraction
Open chain: lat rotation of tibia on femur
Closed chain: med rotation of femur on tibia
3 factors: shape of the medial femoral condyle, tension in the ACL, lateral pull of quadriceps
Popliteus unlocks, med rotates knee
Function of popliteus
Unlocks the knee
Medially rotates tibia on the femur
Laterally rotates femur on the tibia
Knee flexors and innervation
Hamstrings (sciatic nerve): semimembranosus, semitendinosus, biceps femoris
Sartorius (femoral nerve)
Gracilis (obturator nerve)
Gastroc (tibial/sciatic nerve)
Knee extensors and innervation
Quadriceps (femoral nerve): rectus femoris, vastus lateralis, vastus medius, vastusintermedius
How are the hamstrings and quads used in everyday life?
Hamstrings: eccentrically (gait)
Quads: concentrically and eccentrically
Knee rotation ROM, arthrokinematics, muscles
Arthrokinematics: spin (transverse plane)
Muscles: lateral (TFL, biceps femoris, lateral gastroc); medial (popliteus, sartorius, semimem, semitend, medial gastroc, gracilis)
Functions of the patella
Increases internal moment arm of quads (assists in knee extension)
Decreases JRFs at femur
Decreases friction between quadriceps tendon and femur
Kinematics of Patellar Tracking
Knee extension: superior glide, slight lateral glide
Knee flexion: inferior glide, minimal medial glide & tilt
Accessory Motions of Patella
Full extension: patella begins laterally
Full extension to 30* flexion: patella glides medially
30-90* flexion: patella glides laterally
PF contact stress
Force = PF joint compression forces (increased compression with increased quad force and knee flexion angle)
Area= contact area between patella and femur (decreased area at ROM extremes, increased area at mid-ranges (60-90*), modified by alignment and movement)
What factors decrease contact stress at the patella?
Factors that increase PFJ compression forces?
Increase quad force requirements
Increase knee flexion angle
PFJ Contact Area in ROM
Extension: patella rests above intercondylar groove against suprapatellar fat pad
Early flexion: contact at inferior pole
Increased flexion: contact area increases, greatest between 60-90*
Late flexion: contact at superior lateral facet and odd facet; patella located inferior to intercondylar groove
If patella is improperly aligned and/or fails to glide, rotate, or tilt correctly, this can lead to?
Restriction in knee joint ROM
Instability of PFJ
Decreased contact area
External torque with knee extension
in weight bearing, external torque = body weight
in non-weight bearing, external torque = weight of leg
Osteoarthritis precursors, capsular pattern
Precursors: ACL deficiency, meniscal damage/tear, atypical alignment (varus/valgus), degenerative changes, obesity
Capsular pattern: flexion > extension
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