Flashcards in Anatomy of the knee Deck (59):
Where is the knee joint?
Articulation between distal femur and proximal tibia
Articulation between femur and patella
What type of joint is the knee?
Synovial bicondylar hinge joint
List the functions of the knee
- Some rotation when flexed
List the bony structures which strengthen the knee
- Bony expansions
- Locking mechanism
- Femoral angle
List the soft tissue structures which strengthen the knee
List the bony expansions of the knee
What is the function of the bony expansions?
Provides a strong base
What is the function of the locking mechanism
Reduces amount of energy required when extended
Describe the shape of the femoral surfaces in flexion
Describe the shape of the femoral surfaces in extension
What constitutes the locking mechanism
Shape of the femur
Centre of gravity
What does medial rotation of the femur on the tibia in extension do?
Tightens the ligaments of the knee
Where is the centre of gravity in the knee?
In front of the knee
What is the function of the centre of gravity in the knee?
Describe the femoral angle
Adducted femur brings knee joint under pelvis
Critical for weight bearing
Occurs during development
What is normal joint alignment in the knee?
Vertical line through centre of femoral head,
Centre of knee and centre of ankle
Describe varus deformity (Genu varum)
Deformity in the angle tween the femur and tibia
Medial displacement of the tibia - common in children under 2 and rickets
Pushes the knees apart - bow legged - decrease in Q angle
Describe valgus deformity (Genu valgum)
Lateral displacement of the tibia
- Common in children aged 2-4, rickets, arthritis
Brings knees together - ‘Knock-kneed'
Increases Q angle
What is the function of the ligaments in the knee?
Name the two groups of ligaments in the knee
Where are the Extracapsular ligaments found?
Outside of the capsule
Where are the Intracapsular ligaments found?
Inside the capsule
Name the Extracapsular ligaments
- Medial collateral
- Lateral collateral
Name the Intracapsular ligaments
- Anterior cruciate
- Posterior cruciate
Describe the lateral/fibular collateral ligament
Strong round cord
Prevents medial displacement of the tibia
What is a varus deformity?
Tear of the LCL
Describe the medial/tibial collateral ligament
Broad flat band
- Reinforces joint capsule
- Prevents lateral displacement of tibia
What is a valgus deformity?
Tear of the MCL
Where is the anterior cruciate ligament?
anterior in relation to the tibia
Where is the posterior cruciate ligament?
Posterior in relation to the tibia
What is the function of the anterior cruciate ligament
Prevents anterior displacement of tibia on femur
What is the function of the posterior cruciate ligament?
Prevents posterior displacement of tibia on femur
Stabilizer when knee is flexed
What is the function of both cruciate ligaments?
Maintain femur against tibia
Which is the weaker cruciate ligament?
Describe injury to the anterior cruciate ligament
- Common sports injury
- Caused by sharp twisting of knee
- Immediate decreased range of movement
Describe the lachman test
- Patient in supine position with knee bent 20-300 of flexion
- Move tibia anteriorly and posteriorly while maintaining position of femur
- Laxity during this manoeuvre indicates anterior cruciate ligament injury
What are the menisci of the joints
Crescent-shaped plates of fibrocartilage
- Deepen the articulating surfaces/stability
- Shock absorbers
- Provides smooth viscous film for joint
Describe the menisci attachments
Horns of menisci attached to intercondylar area of tibia
Mobile - Accommodates rolling of femoral condyles
Medial meniscus less mobile- Attached to medial collateral ligament
What can be commonly ruptured in the knee?
- Anterior cruciate ligament
- Medial collateral ligament
- Medial meniscus (attached to MCL)
Describe the iliotibial tract
- Reinforces joint capsule
- Stabilizes extended knee
(gluteus maximus, tensor fascia lata)
List the 4 heads of the quadriceps
What is the function of the quadriceps
major stabilizing muscle of the knee
Extends the leg
Describe the patellar
- Protects quadriceps tendon from stresses during locomotion
- Smooth oval facet of posterior surface for articulation with femur
How can the patella be fractured?
due to fall or blow to the knee
How can the patella be dislocated?
sudden twisting/jumping or ligamentous laxity
Name the 3 hamstring muscles
- Biceps femoris
What is the function of the hamstring muscles
- Also medially and laterally rotates leg when knee flexed
- And extends thigh
Which 2 muscles flex the leg?
Hamstrings and gastrocnemius
Describe how the extended leg can be unlocked
Popliteus unlocks knee joint
- Laterally rotates femur on tibia when foot is on ground
Describe the synovial membrane
From margins of articular surfaces of femur to tibia
Attached to patella
Extends superiorly behind quadriceps tendon
Cuffs anterior surface of cruciate ligaments
What is the function of the infrapatellar fat pad?
separates synovial membrane from patellar ligament
What is the function of bursae?
- Reduce friction
What are bursae?
Synovial fluid filled sac lined by synovial membrane
What is bursitis?
Inflammation of bursae
Due to repetitive movements or direct pressure
Describe Prepatellar bursitis
Seen in carpet fitters
Leaning forward on the knees brings the prepatellar bursa in contact with floor
Describe Infrapatellar bursitis
- After prolonged periods of prayer clergymen sat back on their heels bringing infrapatellar bursa in contact with floor
Describe Bakers (popliteal cyst)
Abnormal fluid filled sacs in popliteal fossa
- Due to herniation of synovial membrane/bursa
Common in patients with chronic
inflammatory joint disease (e.g. arthritis)
- Presents as swelling in the popliteal fossa
- Can affect joint movement
How do you treat bakers cyst?
aspiration and cortisone injection