Knee Flashcards
What bones are involved in the knee joint?
Femur, tibia, patella
What type of joint is the knee joint?
Modified ginglymus joint (hinge joint)
Provides flexion and extension
Joints of the knee
Tibiofemoral joint
Patellofemoral joint
Tibiofemoral joint
Proximal concave tibia articulated with the convex distal femur
What makes the tibia concave for the tibiofemoral joint?
Meniscus
Patellofemoral joint
articulation of posterior surface of the surface of the patella and the trochlear surface of the anterior femur
What is the Q Angle?
Alignment at patellofemoral joint formed between a line connecting the ASIS to the midpoint of the patella and a line to the tibial tuberosity
What is a normal Q-angle?
185-190 degrees
What can a smaller than normal Q-angle cause?
increased medial knee pressure
What can a larger Q-angle cause?
Increase lateral knee pressure
Genu Valgum
(knock kneed) q-angle greater than 190….5-10 is normal and normally higher on females
increase compression in lateral compartment of the knee
Genu Varum
(bow legged) knee angle less than 170…less common.
Can be predisposed by: coxa vara-angle less than 125/weak hip abductors
increase compression in medial compartment of knee
Genu Recurvum
(hyperextension) extension beyond +10 of neutral
area of condyles in contact during end range extension is decreased resulting in increased compressive forces secondary to smaller area
Proximal Tibioiblar
Articulation of the proximal tibial and fibula
What are some functions of the proximal tibiofibular joint?
Dissipation of torsional stresses applied at ankle
Dissipation of lateral tibial bending movements
Tensile weight bearing (most joints have compressive forces)
movement occurs with movement of ankle
Does proximal tibiofibular joint move the same or opposite direction of the distal tibiofibular joint?
Opposite
What type of joint is the tibiofemoral joint?
Double condyloid synovial joint
Tibiofemoral Joint
3 degrees of freedom convex femur articulates with concave tibia 2 perspectives (tibia on femur-open/femur on tibia-closed)
Arthrokinematics of Tibiofmoral Joint
Open Chain-Roll and Glide occur together
Closed Chain-Roll and Glide opposite
Tibia on Femur Arthrokinematics
(concave on convex)
Extension: Anterior Roll and Glide
Flexion: Posterior Roll and Glide
IR/ER=spin?
Femur on Tibia Arthrokinematics
(convex on concave)
Extension: Anterior Roll and Posterior Glide
Flexion: Posterior Roll and Anterior Glide
IR/ER: Spin?
Tibiofemoral Closed
Full Extension w/ ER
Tibiofemoral Open
25-30 Knee Flexion
Tibiofemoral Capsular Patter
Flexion > Extension
Screw Home Mechanism
Occurs in the final 20-30 degrees of knee extension
If the foot is planted on the floor with knee flexed, extension of the knee causes:
-ACL to become tight which restrits movement of lateral femoral condyle
-Medial condyle isnt so keeps moving
-causes tibial ER (Femoral IR)
-This “locks” the knee at full extension
what happens if this lock knee does not occur?
Other joints compensate, shortened flexors and lengthened extensors
What muscle unlocks the knee?
Popliteus - causes the tibia to medially rotate during flexion of the knee
Patellofemoral Joint
Patella slides along fixed intercondylar groove in open chain
Intercondylar groove slides along fixed patella in closed chain
most commonly referred at open chain
What is a function of the patellofemoral joint?
increases the angle of insertion for quads and increases the torque producing capacity for quads
Gliding motions of patellofemoral joint
flexion and extension (superior and inferior glides) medial and lateral glides medial and lateral tilts medial and lateral rotation anterior and posterior tilts
Patella Alta
High Riding Patella
Increased length of patella tendon and higher chance of subluxation
Patella Baja
Low riding patella
shortened patella tendon…increases compression can lead to arthritis
Contraction of quads causes a ______ compressive force on the patella.
increased
What type of joint is the proximal tibiofibular joint?
Plane synovial joint
Proximal Tibiofibular Joint
Proximal fibular slightly convex articulating with the slightly concave proximal tibia 3 degrees of freedom -anterior/posterior -superior/inferior -rotation
Tibiofibular joints open positions
0 degrees plantar flexion
Tibiofibular joints closed position
full ankle dorsiflxion
Tibiofibular joints capsular pattern
pain with biceps femoris muscle contraction
Lateral Patellar Tracking
*Tight lateral bands
ITB
Bowstringing (more common in runners)
Lateral patellar retinacular fibers
Medial Patellar Tracking
*tight medial fibers/muscle activity
VMO
Raised lateral facet
Medial Patellar retinacular fibers
External Force Patellar Tracking
Valgus force (increased genu valgum-to compensate)
ER of femur
IR of Tibia
What are the effects of patellar tracking?
increased tension at Quadricep Tendon and Patellar Tendon
increases bowstringing force
Where is the Anterior Cruciate Ligament (ACL) located?
Attaches to the anterior tibia and runs in a posterior, lateral, and proximal direction attaching to lateral femoral condyle.
What are the bands of the ACL?
Anteromedial
Intermedial
Posterolateral
What are the functions of the ACL?
- most effective in extension
- resist excessive tibial anterior slide/translation
- resist excessive femoral posterior slide/translation
- Resist excessive axial rotation, varus and valgus
- resists knee extension (prevent hyperextension)
Which bands of the ACL are tight/slack in knee extension?
posterolateral band tight (control rotation at tibia) and anteromedial band is slack
Which bands of the ACL are tight/slack in knee flexion?
Posterolateral band is slack
Anteromedial band is tight
How is the ACL injured?
Large valgus force with foot planted
Large axial rotation force applied with foot planed
Combination of the previous two
Severe hyperextension
What is the Terrible Triad
ACL, MCL, Medial Meniscus
Can cruciate ligaments repair on their own?
No
Where is the Posterior Cruciate Ligament (PCL) located?
Attaches to the posterior tibia and runs in a proximal, medial and anterior direction attaching to the medial femoral condyle
What is the function of the PCL?
Most effective in flexion
Resist excessive tibial posterior slide/translation
Resist excessive femoral anterior slide/translation
Resist excessive axial rotation, varus, and valgus forces
How is the PCL injured?
Falling on fully flexed knee with proximal tibia striking 1st
Force posterior translation of tibia
Worse with increasing flexion
Rotation, varus, and/or valgus force applied w/ foot planted
Severe hyperextension w/ gapping to posterior side
Where is the Medial Collateral Ligament (MCL) located?
Superficial Portion - Attaches proximally to the medial femoral epicondyle and distally and shaft of the tibia and tibia condyle
Deep portion- attaches to medial meniscus and blends with joint capsule
What is the function of the MCL?
Resists valgus force, knee extension, reinforce medial capsule and prevent ER of leg with knee extended
How is the MCL injured?
Valgus force with foot planted or severe hyperextension
- most commonly torn with ACL
Where is the Lateral Collateral Ligament (LCL) located?
Runs from the lateral epicondyle of the femur to the head of the fibula
Does the MCL or LCL attach to adjacent meniscus?
Only the MCl
What is the function of the LCL?
Resist varus force Resist knee extension Prevent ER of the leg (with knee extension) Reinforce lateral capsule Reinforce posterior-lateral capsule
How is the LCL injured?
Varus force with foot planted
Severe hyperextension
What structures reinforce the capsule of the knee anteriorly?
Connective tissue (patellar tendon and retinacular fibers) Muscular - tendinous (quads)
What structures reinforce the capsule of the knee laterally?
Connective tissue (LCL, lateral retinaculum, ITB) Muscular-tendinous (biceps femoris, popliteus, gastroc)
What structures reinforce the capsule of the knee posteriorly?
Connective tissue (oblique popliteal ligament, arcuate ligament) Muscular-tendinous (gastrocs, hamstrings)
What structures reinforce the capsule of the knee posterior-lateral?
Arcuate complex, LCL
Popliteus
What structures reinforce the capsule of the knee medially?
Retinaculum, MCL, posterior-medial capsular, posterior oblique ligament
Pes anserine
What muscles have an insertion point that make the pes anserine?
Semitendinosus, gracilis, sartorius
What is the most common orthopedic repair?
Meniscus
What are the meniscus?
Fibrocartilaginous discs
Located directly between the femoral condyles and the tibial plateau
Why does the meniscus have limited healing potential?
the meniscus only has a peripheral blood supply so it cannot heal on its own
What is the function of the meniscus?
Deepen surface of the tibia
makes a concavity atop the tibial plateauj
Shock absorbers (compression provides nutrients?)
Which meniscus is more likely to be injured?
Medial by 2X
What are characteristics of the medial meniscus?
larger and more C-shaped
anterior and posterior horns
Firms attachment to the MCL and medial capsule
Why is the medial meniscus more frequently injured?
Due to firm attachment to the tibia and decreased mobility makes it more prone to injury
What are characteristics of the lateral meniscus?
More circular shape, loosely attached to tibia and absorbs more of the stress for less inury
What soft tissues attach to the meniscus?
MCL and semimembranosus to Medial
Poplieus to Lateral
How does the menisci move during knee extension?
menisci move anteriorly with tibia
How does the menisci move during knee flexion?
menisci move posterior with tibia
How are the menisci injured?
axial rotation and valgus force most common
50 percent of all ______ tears associates with meniscal injury.
ACL
Injury can be associated with early onset ________
Osteoarthritis……less cartilage = less shock absorption
What is the function of bursae in the knee?
Reduces friction between the moving structures
Infrapatellar Fat Pad
Between the patellar tendon and tibia
Very sensitive
Helps reduce friction in the knee
What muscles extend the knee?
Quads -rectus femoris -vastus medialis -vastus lateralis -vastus imtermedius Articularis genu
What muscles flex the knee?
Hamstrings -semitendinosus -semimembranosus -bieps femoris (long and short head) Sartorius Gracilis Popliteus Gastrocnemius Plantaris
What knee flexor is not biarticular?
Popliteus
What is the length tension relationship?
Muscles at full contraction or extension lose contractile capabilities
Active insufficieny
Extreme shortened muscle results in decreased motor recruitment (must shorten over both joints)
Passive insufficiency
Tightened/lengthened muscles causes decreased muscle contraction
