T2 L10: Anatomy of the knee Flashcards
The knee joint is the articulation between which bones?
The distal femur and the proximal tibia
What type of joint is the knee joint?
A synovial bicondylar hinge joint
What forms the synovial capsule around the knee joint?
The tendons that surround the patella
What is the function of the tibial condyles?
Also known as the tibial plateau, they receive the femoral condyles
Which factors provide stability for the knee joint and how?
- Bony expansions: The bones have condyles and fossa’s that all articulate
- Locking mechanism: There is a round and flat surface on either side. Medial rotation tightens ligaments of the knee. The centre of gravity maintains extension
What is the difference between the anatomical and femoral angle of the femur?
Anatomical is the one that passes through the femur (at an angle)
Mechanical is the one that bears the weight (vertical)
What is Genu varum?
There is medial displacement of the tibia causing ‘bow legs’
Knee’s are apart so there is increased stress resulting in degradation in joint
What is genu valgum?
Lateral displacement of the tibia causing the knee’s to be too close together
Causes ‘knock- knee’s’ and increased stress on the joint resulting in degradation knee’s’
What are the types of ligaments at the knee joint?
Extracapsular: medial and lateral collateral ligaments
Intracapsular: anterior and posterior cruciate ligaments
What does tearing of the lateral collateral ligament result in?
Varus deformity
What does tearing if the medial collateral ligament result in?
Valgus deformity
What is the origin and insertion of the cruciate ligaments?
Origin: lateral femoral condyle
Insertion: intercondylar area
How do you know which cruciate ligament in the knee is posterior?
It’s in relation to the tibia
Anterior to their position on the tibia or posterior
What is the function of cruciate ligament?
They prevent anterior and posterior displacement of the tibia on the femur
They maintain the femur against the tibia. At least 1 ligament is always tense
What happens to the cruciate ligaments during medial and lateral rotation of the leg?
Medial: ligaments tighten so there is limited rotation
Lateral: ligaments unwind
Which cruciate ligament is most frequently injured?
The anterior cruciate ligament is weaker. It’s a common sports injury caused by sudden rotation of the knee
What is the Lachman test?
A passive accessory movement test of the knee performed to identify the integrity of the anterior cruciate ligament
It involves moving the tibia up and down while maintaining position of the femur to look for looseness
What is the menisci of the knee joint?
The medial and lateral menisci provide a deepening of the articulating surfaces to increase stability
Which surfaces of the menisci in the knee are mobile?
Only the anterior and posterior bits are attached to the intercondylar area. The rest is mobile
Why is the medial meniscus less mobile than the lateral meniscus?
Because the medial meniscus is attached to the medial collateral ligament
What is an unhappy triad injury?
Twisting on a flexed knee and a blow to the lateral side during contact sports like rugby
Causes rupture of the anterior cruciate ligament, medial collateral ligament, and the medial meniscus
Why is the unhappy triad injury so hard to repair?
Because there is poor blood supply to the intracapsular structures
It generally requires surgery
What is the function of the iliotibial tract?
It’s the deep band of fascia on the leg that stabilises the joint capsule
Which muscles insert onto the iliotibial fascia?
Gluteus maximus and tensor fascia lata
What is the group of muscles that extend the leg?
The quadriceps
- Rectus femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
Which structures form the extensor mechanism?
The quadriceps tendon, patella, and patellar ligament
What is the function of the patella?
It’s a triangular-shaped sesamoid bone that protects the quadriceps tendon from stresses during locomotion
What are the aponeurotic expansions of vastus lateralis and medialis called?
Lateral and medial patellar retinaculum
They help stabilise the patella
What is a sesamoid bone?
One that forms between tendons
Which group of muscles are the flexors of the leg?
The hamstrings
- Biceps femoris
- Semimembranosus
- Semitendinosus
What is the origin of the hamstrings?
The ischial tuberosity
What is the function of the popliteus muscle?
It unlocks the knee joint at the back of the knee
It laterally rotates the femur on the tibia when the foot is on the ground
Which spaces does the popliteus muscles pass through?
Passes through the joint capsule and the space under the lateral collateral ligament
What are the names of the bursae within the knee joint?
- Suprapatellar bursae
- Prepatellar bursae
- Infrapatellar bursae
They protect and reduce friction
Which patellar bursae is continuous with the synovial membrane?
The suprapatellar bursae
Where are bursae found?
Anywhere where there is friction including between tendons
What causes prepatellar bursitis?
Known as ‘housemaid’s knee’
Caused by continuous leaning forward of the knee which brings the patellar bursa in contact the the floor
Common in carpet fitters
What causes infrapatellar bursitis?
Also known as clergyman’s knee
Caused by prolonged sitting on your heels which brings the infrapatellar bursa in contact with the floor
What causes a popliteal cyst?
Also known as a bakers cyst
Caused by herniation of the bursa. Common in people with chronic inflammatory joint disease
How is a popliteal cyst treated?
By aspiration and cortisone injection
Which arteries form the knee anastomosis?
The femoral and popliteal artery
Poor blood supply to the intracapsular structures
