Knee Flashcards
What is the osteology of the tibiofemoral joint and the patellofemoral joint?
What type of joint?
Femur, Tibia, Patella
Tibiofemoral = modified hinge
What is normal tibiofemoral alignment? What is genu valgum? Genu varum?
Normal = 170-175 femoral shft laterally from tibial shaft Valgum = (knock knees) <165 Varum = (bow legs) >180
What compartment is compression in genu valgum? Genu varum?
Valgum - lateral compression
Varum - medial compression
What factors can lead to genu valgum?
Previous injury Genetic predisposition High body mass index Laxity of ligaments Abnormal alignment & muscle weakness at either end of the lower extremity
What factors can lead to Genu varum?
- Previous injury
- Genetic predisposition
- Laxity of ligaments
- Abnormal alignment & muscle weakness at either end of the lower extremity
- Thinning of articular cartilage on medial side can result in genu varum (only one different)
What might result from genu valgum?
Increased stress on MCL, increased stress in lateral compartment
Excessive lateral tracking of the patella
Increased stress on ACL
What might result from Genu varum?
Increased medial compartment loading
Greater loss of medial joint space
Increased strain on LCL
What is genu recurvatum? Where is the stress placed with this posture?
- Hyperextension at the knee when standing
- Overstretched posterior capsule and paralyzed knee flexors
What are the attachments and function of the meniscus?
Distribute weight bearing forces
Increase joint congruence
Shock absorption
Medial meniscus
Less mobility due to greater ligamentous restraint
Attachments:
Connections to MCL, ACL, PCL, semimembranosus
What is the lateral meniscus connected to?
MCL, PCL popliteus
What part of lateral meniscus is vascularized?
Periphery
What motions does the ACL restrict?
Primary - restraint to anterior translation of tibia on femur
-Also hyperextension, varus/valgys, tibial rotation medial/laterally
What motions does the PCL restrict?
Primary - posterior translation of tibia on femur
-Also varus and valgus stresses, tibial rotation medial
What motions does the MCL restrict?
Primary - valgus and lateral tibial rotation
-Also anterior translation of tibia on femur
What motions does the LCL restrict?
Primary - varus
-Also tibial rotation laterally
ACL 3 factors associated with non-contact injuries:
Strong activation of quad over moderately flexed or nearly extended knee
Marked valgus collapse of the knee
Excessive ER of the knee
PCL factors associated with injuries:
- Associated with high-energy trauma: contact sports
- MOI
1. Falling on to fully flexed knee with ankle plantar flexed (proximal tibia his ground first)
2. “Dashboard” injury - Posterior sag sign
Describe the osteo of the tibiofemoral joint.
Flex/Ext
IR/ER (arthro not defined)
Abduction/Adduction (arthro not defined)
Describe the arthrokinematics of the tibiofemoral joint.
Flex OKC and CKC=
OKC = posterior roll/glide CKC = Posterior roll/ant glide
Describe the arthrokinematics of the tibiofemoral joint.
Ext OKC and CKC=
OKC = Anterior roll/glide CKC = Anterior roll/post glide
What is terminal extension of the knee?
Need 10 degrees of ER to fully extend knee
Describe the screw home mechanism at the knee
Knee must unlock (popliteus) prior to performing flexion by 1st medially rotation then flexing
What is the open pack position and capsular pattern at the tibiofemoral joint?
Open pack = 25 flexion
Capsular pattern = flex»_space; ext
Describe the joint congruency of the patellofemoral joint and the changes that occur in it with knee flexion.
Full ext = patella lies on femoral sulcus so minimal joint congruency here -> greater chance for instability
Why is important for us to have a patella?
- Acts as spacer/pulley between femur and quad
2. Increase internal moment arm of knee extensors
What structures help stabilize the patella?
Reliant on static and dynamic structures for stability secondary to incongruence of PF joint Lateral patellofemoral ligament Medial patellofemoral ligament Medial patellotibial ligament Lateral patellotibial ligament Quadriceps Trochlear Groove
Describe the motions of the patella.
- Inferior/superior glide with flex/ext
- Medial/lateral glide: frontal plane translation
- Medial/lateral tilt
- Medial/lateral rotation
Put in order from least to most the compressive forces at the patellofemoral joint during squatting, walking, and climbing stairs.
- 1.3 body weight with walking on level surface
- 3.3x body weight with climbing stairs
- 7.8x body weight with deep squats
What is the Q angle? What is a normal Q angle? Why do we care?
q angle - line connecting ASIS to middle of patella
-estimation of line of pull of quads
Normal - 13-15
-Increased Q angle increases lateral force on the patella
Describe local factors that may limit lateral pull of the patella.
Raised lateral facet of trochlear groove
Quadriceps in particular VMO
Medial patellar retinacular fibers
Medial passive structures
Describe local factors that may contribute to lateral pull of the patella.
- Tight IT band or excessive tension in lateral patellar retinacular fibers or lateral passive structures may increase lateral pull
- Decreased fit of patella within trochlear groove of femur
Describe global factors that may contribute to lateral pull of the patella.
- Excessive Genu valgum increases Q-angle
- Weakness of hip abductors/ER, or tightness of adductors/IR
- Excessive pronation (eversion) of subtalar joint also can create excessive valgus load
What are the recommendations for weight bearing and non weight bearing exercises for patellofemoral pain syndrome?
-Recommended avoid deep flexion in weight bearing, and avoid final 30 degrees of extension during non-weight bearing
