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Functional Anatomy > The knee- Palastanga > Flashcards

The knee- Palastanga Flashcards

1
Q

Classification

A

(Modified) Synovial bicondylar hinge

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2
Q

Articulations

A

3- 2 femorotibial and 1 femoropatellar

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3
Q

How does it’s classification suit the knee joint

A

It allows movement in only one direction, conferring stability and satisfying the requirement of a wieght bearing joint

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4
Q

When is the knee most stable

A

In extension

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5
Q

What is the value of the femortibial angle and what causes this

A

Between 170 and 175 degrees

Difference/ angle between the anatomical axes of the femur and tibia

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6
Q

The joint centres of the hip, knee and ankle all form a straight line to form what?

A

The mechanical axis of the lower limb, which sits about 3 degrees off vertical

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7
Q

Describe the mechanical axis of the lower limb with regards to the various anatomical axes

A

Coincides with the anatomical axis of the tibia

Forms an angle of about 6 degrees with the anatomical axis of the femur

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8
Q

What is genu valgus

A

Knock knees - femorotibial angle is decreased

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9
Q

What is genu varus

A

Bowlegs - femorotibial angle is increased

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10
Q

How do the femoral condyles differ and why is this important

A

The medial condyle juts out more, makes lateral displacement of the patella more likely (also due to quad pull)

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11
Q

Describe the femoral condyles

A

Convex in both planes and longer AP than transversely

Long axis of each is not parallel but diverge posteriorly

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12
Q

Describe the tibial plateau

A

Separated from eachother by the intercondylar eminence
Are relatively flat
Lateral surface is smaller
Articular surfaces deepened by the menisci

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13
Q

Describe the articular surface of the patella

A

Oval
Larger lateral and smaller medial areas divided by a vertical ridge which corresponds to the patellar surface of the femur
Thickest cartilage of anywhere in body due to high stresses

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14
Q

Describe the joint capsule

A

Is incomplete and mainly formed of muscle tendons and their expansions
Strengthened by associated ligaments

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15
Q

Which ligaments help to strengthen the capsule

A

Oblique popliteal ligament (posteriorly in the central region)
Arcuate popliteal ligament (laterally)

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16
Q

Describe the collateral ligaments of the knee

A

Medial collateral ligament- strong flat band attaching to the medial meniscus
Lateral collateral ligament- Rounded cord separate from capsule, attaching to lateral surface of head of fibula

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17
Q

Features of the synovial membrane of the joint

A

Excludes the cruciate ligaments
Alar folds (of synovium) project from the edge of the patella into the joint and cover collections of fat
2 other folds called plicae also observed which may become trapped and inflamed

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18
Q

What is the significance of the infrapatellar fat pad

A

Pushes the synovial membrane in this area deep into the joint
Is the remains of a septum which divided the embryonic knee into 2 compartments

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19
Q

What are the intra-articular structures of the knee

A

Cruciate ligaments

Menisci

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20
Q

How are the cruciate ligaments described

A

Depending on their attachment to the tibia
i.e ACL attaches anteriorly on tibia
Are mainly composed of collagen

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21
Q

Describe the anterior cruciate ligament

A

ACL originates anteriorly on tibia and undergoes a 110 degrees spiral before attaching to the medial surface of the lateral femoral condyle
Divided into 2 bands
-anteromedial taut in flexion
-posterolateral taut in extension
Resists ant displacement of tibia on femur

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22
Q

Describe the posterior cruciate ligament

A

PCL originates from tibia posteriorly and runs anteriorly, medially and proximally to attach to the lateral surface of the medial femoral condyle
Divided into 2 bands
-anterolateral
-posteromedial
Resist ant displacement of femur on tibia

23
Q

When is rotation of the knee permitted

A

When the knee is flexed (only a very small degree allowed)

24
Q

What are some of the proposed functions of the menisci

A 
Increase the congruency of the joint
Act as shock absorbers
Participate in weight bearing
Participate in the locking mechanism
Provide lubrication
25
Q

What makes up the menisci

A

Fibrocartilage

26
Q

Describe the menisci

A

Crescent shaped with triangular cross section and free inner edge
Medial is larger
Lateral is freer
Vascularity is poor, only peripheral 20% supplied in adults

27
Q

Which meniscus is more commonly injured, how and why

A

Usually the medial meniscus due to its attachment to the MCL

Usually happens through rotation, particularly on a planted foot

28
Q

What is the blood supply to the knee

A

Genicular anastamosis involving 10 vessels, 5 of which are branches of the popliteal artery

29
Q

What mainly confers stability to the knee

A

The collateral and cruciate ligament, reinforced by musculotendinous ties across the joint

30
Q

How is rotations of the knee prevented

A

(Especially when the knee is extended) tension in the collateral and cruciate ligaments prevents this

31
Q

Describe the range of flexion of the knee

A

Active flexion may reach 140 degrees if hip is flexed, 120 degrees when it is extended due to loss of efficiency of hamstrings
Passive flexion 160 degrees (sitting on your knees)
Is limited by contact of the heel with the buttocks

32
Q

How is maximum flexion of the knee achieved

A

Passively

33
Q

What is the significance of the hamstrings in knee movement

A

Are hip extensors as well as knee flexors so knee movement depends on the position of the hip and vice verse

34
Q

How is movement of the femoral condyles achieved

A

A combination of rolling and gliding which varies through movement, causing the joint centres to move

35
Q

What is hyperextension of the knee and how much is allowed

A

Movement (usually passive) of the tibia beyond the alignment of the long axis of the leg and femur
Usually only up to 5 degrees is allowed
May be seen in hypermobility

36
Q

How does the patella move during knee movement

A

During knee flexion is pulled tightly against femur by quadriceps tendon
During extension this decreases and the patella may separate from the femur, this is when transverse displacement is most likely to occur

37
Q

What is the direction of pull on the patella and why

A

Usually pulled laterally due to quadriceps

38
Q

Describe patellar dislocation

A

Usually occurs laterally and when knee is extended
May be due to an underdeveloped lateral lip or weakness in vastus medialis
More common in females due to wider pelvis and increased femortibial angle

39
Q

What are the ranges of rotation possible at the knee

A

(With knee flexed to 90degrees)
Medial rotation- 30d active 35d passive
Lateral rotation- 40d active 50d passive

40
Q

What is the approximate level of force across the femorotibial joint during gait

A

2 to 4 times body weight

41
Q

What is approximate force on the patella during gait

A

Half of body weight

42
Q

When does femoropatellar force increase and to what level

A

During ascending and descending ramps or stairs may increase to between 2.5 and 3 times body weight

43
Q

When is the greatest femoropatellar force sustained

A

When rising from a chair without using the arms- 3.5 times body weight

44
Q

What happens to femorotibial forces during ascending and descending stairs/ ramps

A

Relatively little change

45
Q

What happens to femorotibial and femorpatellar joint forces during jumping

A

Femorotibial- may reach around 24 times body weight

Femoropatellar- may reach around 20 times body weight

46
Q

Forces across the joint are mainly in what direction

A

Vertical

Mediolateral forces very low

47
Q

Which side of the femorotibial joint receives the greatest force

A

The lateral (due to the shape)

48
Q

Describe the trabecular pattern of the femur

A

2 sets running into each condyle, one from the same side and one from the contralateral side(4 total)
1 set running transversely to unite the condyles

49
Q

Describe the trabecular pattern of the tibia

A

A mirror of the femur
2 sets for each tibial condyle, one from the ipsilateral side and one from the contralateral (4 total)
1 set uniting the condyles

50
Q

Which muscles flex the knee

A 
Hamstrings
Gracilic
Sartorius
Popliteus
Gastrocnemius
51
Q

Muscles extending the knee

A

Quadriceps

Tensor fascia lata

52
Q

Which muscles laterally rotate the tibia at the knee

A

Biceps femoris part of hamstrings

(only part that attaches laterally)Musc

53
Q

Muscles medially rotating the tibia at the knee jt

A

Semitendinosus and semimembranosus part of hamstrings
Gracilis
Sartorius
Popliteus

54
Q

What is the function of the patella

A

From 30-70d flexion is solely responsible for transferring quadriceps force to the femur
Also acts to increase extensor mechanism by increasing the angle at which the extensor muscle acts

Functional Anatomy (18 decks)

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