Lecture 55 - Knee Flashcards
Describe the tibiofemoral joint
Articulates between medial and lateral femoral condyles of femur and the tibial platea (in A/P plane)
Describe the medial femoral condyle
Extends further distally and is larger and rounder than the lateral femoral condyle (in A/P plane)
Describe the lateral femoral condyle
Projects further anteriorly and is wider medial to lateral than the medial femoral condyle
Describe the medial tibial condyle
Longer than the lateral condyle (A/P plane) and it is the insertion point of the semimembranosus muscle
Describe the lateral tibial epicondyle
Describe the formation of the knee angle
Due to lack of bony congruency, the osseus structure is less stable and needs support of associated structures to provide stability. When the vertical tibia and oblique femur are placed together the have an anatomical axis of 185 degrees which generates slight varus at the knee
Describe the difference between genu valgum and genu varum
Medial angle > 185 degrees = genu valgum/locked knees
Medial angle <175 degrees = genu varum/bow legs
What are 4 characteristics of menisci
- Wedge shaped, semi-circular fibrocartilaginous discs on tibial plateau that disperse weight bearing forces
- during weight bearing activities, it can mange 70% of load on knee
- Beginning and end of meniscus are called horns (anterior or posterior based on location and found in sagittal plane)
- Held firmly into edge of joint capsule by canonry and other ligaments surrounding meniscal complex
4 characteristics of medial meniscus
3 characteristics of lateral meniscus
7 functions of the menisci
Describe the blood supply of the meniscus
What are the 3 knee compartments
- Lateral
- Medial
- Patellofemoral
The lateral compartment is subdivided into what 3 areas and what are they supported by
What are 4 characteristics of the lateral/Fibular collateral ligament
The medial compartment is subdivided into what 2 areas and what are they supported by
What are 5 characteristics of the medial collateral ligament
What are 3 characteristics of the knee joint capsule
What are 2 characteristics of the anterior capsule of the knee
What are 4 characteristics of the posterior capsule of the knee
What are 6 characteristics of the cruciate ligaments
What are 2 characteristics of the anterior cruciate ligament
- Originates from posterior-medial corner of lateral femoral condyle and attaches in a fossa anterior/medial to intercondylar eminence
- Made up of a posterior and anterior bundle
Function of posterior/lateral bundle of ACL
Function of the anterior/medial bundle of ACL
What is the overall function/movement of the ACL (3)
- IR of tibia causes ACL to become taut (anterior/medial bundle
- Stabilizes knee against hyperextension and against varus and valgus motion (secondary support)
- Prevents excessive distraction, ER of tibia and guides locking mechanism of knee and motion
Describe non-contact injury to the ACL
Most often a deceleration injury that occurs in a position of slight flexion coupled with medial or lateral tibial rotation
4 characteristics of the posterior cruciate ligament (PCL)
- Comes from lateral aspect of medial formal condyle to a fossa posterior to the tibial tubercle
- Divided into larger anterolateral (95%) and posteromedial (5%) bundles
- Primary restraint to posterior displacement of the tibia on the femur
- Greatest posterior translation resistance is required at 70-90 degrees flexion because secondary restraints (posterior capsule, popliteus and MCL) are too lax to contribute
Function of anterolateral bundle of PCL
Tight in flexion
Function of posteromedial bundle of PCL
Tight in extension
What is the overall function/movement of the PCL
What is the greatest mechanism of injury in PCL tear
Because it is taut in flexion, greatest mechanism of injury is hyperflexion (eg. dashboard injuries)
Note:
ACL = tight in flexion, taut in extension
PCL= tight in extension, taut in flexion
Knee flexion is a combination of
Posterior rolling of the femoral condyles couple with an anterior femoral glide
Knee extension is a combination of
Anterior rolling (posterior glide) of the femoral condyles
There is a slight amount of valgus associated with knee [blank]
extension
There is a slight amount of varus associated with knee [blank]
Flexion
Describe the screw home mechanism of the knee
To lock the knee (terminal knee extension): The tibia laterally rotates to lock the knee into extension (open)
Femur internally rotates to lock knee into extension (closed)
To unlock the knee (move into flexion):
Open chain: popliteus contracts to internally rotate the tibia
Closed chain: popliteus contract to externally rotate the femur
Describe the impact of therapeutic exercises on the knee
Weight-bearing exercises create less anterior sheer forces on the knee….instead exercises such as squat and leg press have demonstrated increased posterior sheer force through 80-100 degrees of knee flexion
Differentiate between genu valgum and varum of the knee
Where does the patella sit during knee extension
In the trochlear groove (apex is only in contact with femur)
Patella Alta
When patella sits high in trochlear groove and infrapatellar tendon is elongated
Patella Baja
When patella is low in trochlear groove and infrapatellar tendon is shortened
When there is greater than 90 degrees of knee flexion the patellar contact shift
Inferiorly and laterally to load the odd (extreme medial edge of patella which contacts femur in deep flexion) and lateral facets
Patellar Plicae
Folds that contain the synovial membrane of the knee
What are the 2 types of patellar plicae
- Superior plicae: Above superior patella
- Inferior plicae (ligamentum mucosum): Attaches from intercondylar fossa to inferior pole of patella
Plicae Syndrome
Pain that develops in the patellar plicae folds
Patellofemoral joint capsule is exposed to
High stress during activity because of high forces (motion and quadricep muscles = compression) and small contact area
Where are the patellofemoral contact areas
What causes patellar instability (3)
1) trochlear groove is shallow
2) lateral femoral condyle is less prominent
3) patellofemoral soft tissue tethers are lax
What position is patellar instability tested in
Total knee extension because bony stability is reduced and there is less compression on patella from quadricep muscles
What ligament opposes lateral migration of the patella
Medial patellofemoral ligament
The vastus medialis contributes what force on the patella and what happens if the vastus medialis is weak, and how do you treat vastus medialis when its weak
It contributes a medial force vector on patella, so if weak there may be a lateral patellar force. to strengthen this muscle just do quadricep training as it cannot be isolated
What is the Q angle (Quadricep angle) and what is a normative and abnormal value
Line that extends from ASIS to patellar midpoint and a line from midpoint of patella to tibial tuberosity (structural relationship between quadriceps and patella). Normative is 10-15 degrees male or 15-20 degrees female. Anything greater than 20 degrees can put patient at risk of lateral patellar forces.
What are 7 causes of patellar instability
What type of joint is the knee
Tricompartmental
The patellofemoral joint reaction force is the
Compressive force action on the patello-femoral joint which depends on knee flexion angle and muscle force
Are joint forces at the knee variable
Yes it depends on contraction of quads, extensibility of conective tissue, and bony shape of patella dn trochlear grove
What affect does the patella have on mechanical advantage?
It increases the advantage of the quads mechanism increasing the force of knee extension by 30-50%
What are two types of osteoarthritis in the knee that leads to levels of disability and pain
- Patellofemoral Joint
- Tricompartmental joint
What are some strategies to stabilize the patella and prevent osteoarthritis
Describe the blood supply of the knee and why the ACL experiences bleeding when torn
What artery supplies the PCL
Middle geniculate artery
What are the major muscles knee flexors and extensors of the knee (which ones are primary and secondy)
- Hamstrings: Primary flexor (also concurrent posterior displacement of tibia)
- Popliteus, gastric, Sartorius, gracillis, plantaris and TFL are secondary flexors, and internally and externally rotate knee
- Quadriceps: Primary extensor and anteriorly translates tibia and have force vectors in relation to patella
What muscles in the knee are responsible for varus forces
Semimembranosus, semitendinosus, medial head of gastric, Sartorius, gracilis
What muscles in knee are responsible for valgus force
Biceps femoris, lateral gastric, popliteus
Popliteus complex is responsible for (4)
- Monitoring and controlling anterior and posterior lateral meniscus movement
- Unlocking by internally rotating the knee joint (tibia internally rotates on femur) during flexion initiation
- Balance/postural control during single leg stance
- Activating essential mid-range flexion when capsuloligamentous structures are slack
Which 4 structures attach the medial meniscus
Why do natal sex female’s have higher incidence of ACL tears compared to males
Do all ACL tears require surgery
How do you start a knee examination
Describe single leg stance and the systems it challenges and progression
Describe the single leg squat and what it exams
