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BIOMECH SPRING - EXAM 2 > Lecture 9 - Knee muscle and joint interaction > Flashcards

Lecture 9 - Knee muscle and joint interaction Flashcards

1
Q

What muscle group does knee ext? What is their innervation?

A

Quadriceps innervated by the
femoral nerve – the only innervation
to extensors

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2
Q

What is the innervation of the muscles that do IR of the knee?

A
  • Sartorius -femoral
    • Gracilis -obturator
    • SM - Sciatic (tibial)
    • ST - Sciatic (tibial)
    • Popliteus -tibial
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3
Q

What is the innervation of the muscle that does ER of the knee?

A
  • Biceps femoris : Sciatic (tibial & fibular)
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4
Q

What is the innervation of the muscles that do flexion of the knee?

A
  • SM : Sciatic (tibial)
  • ST : Sciatic (tibial)
  • Bicep femoris (long and short) :Sciatic (tibial & fibular)
  • Sartorius/Gracilis : femoral /obturator
  • Gastrocnemius/Plantaris : tibial
  • Popliteus: tibial
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5
Q

What supplies the knee and associated ligaments innervation?

A

Knee and associated ligaments supplied through L3-L5 spinal nerve roots via posterior tibial, obturator and femoral nerves

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6
Q

What is the largest afferent sensory supplier to the knee?

A

Largest afferent to the knee – posterior tibial nerve
- posterior capsule/associated ligs
most internal structures up to infrapatellar fat pad

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7
Q

What do the afferent fibers in the obturator nerve supply in the knee? (sensory)

A

Afferent fibers in obturator nerve
Carries sensation from skin over medial knee and post/post-medial capsule

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8
Q

What do the afferent fibers of the femoral nerve supply sensory innervation to in the knee?

A

Carries sensation from ant-medial and ant-lateral capsule

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9
Q

What should we know about the quadriceps femoris?

A

Cross-sectional area as high as 2.8 X >er than that of the hamstrings

Vastus group = 80% of the total extension torque (knee extension)

Rectus femoris = 20% (hip flexion and knee extension)

Vastus medialis – 2 fiber directions: VMO (30% of entire VM) @ 50-55 deg angle to the tendon & VML @ 15-18 degrees

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10
Q

Where does the rectus femoris run?

A

AIIS & immediately superior to acetabulum

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11
Q

Which quad has the greatest cross sectional area?

A

vastus lateralis

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12
Q

Which quad extends farther toward the knee and has 2 sections?

A

vastus medialis

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13
Q

Which quad muscle is deep to RF and VL
?

A

vastus intermedialis

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14
Q

Which muscle is deep to VI, poorly defined, runs distally into the capsule/synovial membrane (pulls them prox during ext)?

A

Articularis genu

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15
Q

What is the knee extensor mechanism?

A

Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius
- forms strong quadriceps tendon attaches side and base of patella
- Patella tendon connects apex to tibial tuberosity

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16
Q

What are the isometric considerations of the knee ext mechanism?

A

Isometric functions:
- stabilizes to protect the knee

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17
Q

What are the eccentric considerations of the knee ext mechanism?

A

Eccentric functions (like a spring):
- controls the rate of descent of the body’s COM (sitting, squatting landing from a jump)
- dampens impact/loading on the knee: walking - heel contact into loading knee flexion in response to GRF (controls knee flexion)
- Step down

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18
Q

What are the concentric functions of the knee ext mechanism?

A

Concentric functions:
- Accelerates tibia/femur toward extension…raises COG: jump, step up, stand up, running uphill.

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19
Q

With increasing external torque, what happens to the demand on the muscle and underlying joint?

A

increasing demand on the muscle and underlying joint, in response to the increasing external torque.

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20
Q

Where is the largest moment arm/extension torque in 0-90 degrees open chain?
Eccentric or concentric?

A

0 degrees
- concentric

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21
Q

Where is the largest moment arm/extension torque in 0-90 degrees closed chain?
- Eccentric or concentric?

A

90 degrees
- eccentric

22
Q

What are some exercises that minimize stress to joint and still train quads?

A

knee ext with weight 90-45 and partial sit-stand 0-45.

23
Q

When is external torques largest?

A

External torques relatively large from 90-45 degrees for femoral-on-tibia and 45-0 degrees of flexion for tibia-on-femoral extension.

24
Q

What is an extensor lag? Why does it happen?

A
  • Inability to complete full AROM tibial-on-femoral
  • Knee can be fully extended passively
  • Usually, the last 15-20 degrees of extension
  • It occurs where the internal torque potential of the quads (opposing the external torque) is the least and the external torque is the greatest!
25
Q

What is the functional role of the patella?

A

A ‘spacer’ between femur and quadriceps
Increases the internal moment arm of the extensor mechanism
>est between 20 -60 deg

26
Q

What three factors impact the length of the knee ext moment arm?

A

3 factors impact the length of the knee extension moment arm:
1. Shape and position of the patella
2. Shape of the distal femur (depth and shape of trochlear groove)
3. The migrating M-L axis – ‘evolute’

27
Q

What is the difference on the quads in a partial vs deeper squat?

A

> er force from the quads because of the >er external (flexion) torque on the knee in deep squat…
(needs >er internal force)

28
Q

What does greater knee flexion do to the joint angle between the QT and PT?

A

> er knee flexion decreases the angle between QT and PT and thus produces a >er joint force between the patella and femur.

29
Q

What does the force and contact area do with knee flexion?

A

Force and contact area increases with knee flexion - max @ 60 – 90 deg.
Stress = force/area - knee can tolerate the force due to increased area of contact

30
Q

What factors affect patellar tracking?

A

1) Quadriceps
2) Local factors: act directly on the PF joint
3) Global factors: related to alignment of the bones/joints of LE

31
Q

What are the consequences of patellar maltracking?

A

less than optimal congruity = “tracking’ problems of the patella
- Consequence – higher contact stress and risk for degenerative lesions

32
Q

What is the Q angle?

A

also known as quadriceps angle, is defined asthe angle formed between the quadriceps muscles and the patella tendon.
@ 13-15 degrees

33
Q

What is the net lateral pull of the patella indicated by?

A

The net lateral pull exerted on the patella by the quadriceps is indicated by the Q-angle.

34
Q

With a larger Q angle, what happens to the lateral pull on the patella?

A

The larger the Q-angle, the greater the lateral muscle pull on the patella

35
Q

What are local factors that oppose the pull on the patella?

A

act directly on the PF joint - laterally
Large ‘bowstring’ force on patella due to Q angle (reduced contact area, articular stress, risk of dislocation)
Excessive tension in ITB and lateral retinaculum

36
Q

What are global factors that resist the pull on the patella?

A

related to alignment of the bones/joints of LE
- The magnitude of the lateral ‘bowstring’ is influenced by frontal and horizontal plane alignment
- Excessive genu valgum can increase Q angle and ‘bowstring’ force on patella

37
Q

How can patella maltracking laterally happen?

A

Laxity of/injury to MCL
Dynamic posture of adduction of femur (weakness hip abd/tightness of add; compensated Trendelenburg – and GRF shift to lateral knee creating valgus torque; excessive pronation of ST joint (IR of tibia); reduced strength/neuromuscular control of the ER of hip (thus IR of femur)

38
Q

What is patellofemoral pain syndrome?

A
  • One of the most common
  • 30% of all in F, 20% in M
  • Young and active persons
    Diffuse peripatellar/retropatellar pain; insidious onset
  • Squatting, stairs, prolonged sitting with knees flexed
  • Biomechanical reasons – stress intolerance of articular cartilage and innervated subchondral bone
  • Can be difficult to treat!
39
Q

What are the Traditional treatment principles for abnormal tracking and chronic dislocation of the PF joint?

A

Address underlying pathomechanics
No gold standard
Exercises to strengthen/control hip abd/Erot; core; quads (VMO); support longitudinal arch of foot
Stretch tight structures (ITB), mobilize patella, brace/tape patella, orthotics
Modify exercises to reduce load to PF joint/quad torque

40
Q

What are the knee flexor-rotators?

A

Hamstrings, sartorius, gracilis, popliteus – all flex and rotate (gastroc only non rotator)

Rotation – freest in flexion; IR (SM/ST) & ER (BF)

41
Q

What resists knee erot and valgus loads?

A

Sartorius/Gracilis: pes anserine –posterior to knee axis – so IRot; medial knee stabilizer (resists knee ERot and valgus loads)

42
Q

What does the popliteus muscle do? Why is this important?

A
  • Triangular and in the popliteal fossa, intracapsular tendon
  • unlocks the kneeswhen walking, by laterally rotating the femuron thetibiaduring the closed chain portion of thegait cycle(one with the foot in contact with the ground). It is also used when sitting down and standing up.
  • open chain movements popliteus muscle medially rotates the tibia on the femur (IR and flexion)
43
Q

What controls femoral-on-tibial osteokinematics?

A
  • External rotation of the knee (TT points laterally)
  • The short head of the biceps femoris contracts to accelerate the femur internally (i.e., the knee joint moves into external rotation)
  • Active force from the pes anserinus muscles in conjunction with a passive force from the stretched medial collateral ligament(MCL)and oblique popliteal ligament (not shown) helps to decelerate, or limit, the external rotation at the knee.
44
Q

When is there max force of the knee flexor-rotator muslces?

A

Max last 20 degrees of extension
(longest muscular length vs >er leverage)

> est leverage 50- 90 degrees

Flexing the hip (elongates HS) promotes >er torque

At 90 degrees biceps femoris has 3 X greater moment arm (fibular head) than the avg of all internal rotators (all rotators best at 70-90)

Popliteus IRot best at 40 deg

45
Q

What are frontal plane abnormal alignments of the knee?

A

Frontal plane
- NLs 5-10 deg valgus
- Normal walking speeds – level terrain, JRF 2.5-3 X BW (muscles and GRF)
- GRF gives a varus torque
- LCL and ITB absorbs forces – several times >er at medial joint
- Loss of medial joint space makes a larger varus load…..can develop medial joint OA

46
Q

What are some sagittal plane abnormal alignments of the knee?

A
  • Genu recurvatum – LOG anterior to knee – favors extension and rest of quads
  • Hyperextension > 10 degrees – can cause generalized laxity of posterior structures
  • Poor postural control, neuromuscular disease – spasticy of quad/weakness of flexors; overuse/laxity
47
Q

What is Jumper’s knee?

A
  • Patellar tendinopathy
  • Chronic pain in patellar tendon
    Explosive and repetitive jumping (basketball and volleyball)
  • Collagen disorganization and vascular proliferation – overuse and wear
  • With the lack of inflammation is ‘opathy’
  • Training intensity, footwear, playing surface, strength, endurance, flexibility, male gender, patella alta and hypermobility
  • Dorsiflexion – reduced – does not permit ideal dissipation of energy
48
Q

What are some ACL considerations for injury?

A

F 3 X’s more likely than M
- Noncontact sports with jumping/landing/vigorous pivoting motions
- Basketball, soccer, gymnastics
F land in >er valgus than M and more upright

49
Q

What should we know about rehab of the ACL?

A

Avoid exercises where strong/repetitive quad contractions create anterior translations of the tibia (or posterior femur) early on rehab to damage tissue
Muscle line of force changes with flexion angle
Risk (strain to ACL) is when force in opposition to ACL action and muscular force magnitude increases

50
Q

What should we know about the advice given to avoid exercise in early ACL rehab?

A

Advice given to avoid or limit exercise in early ACL rehab reconstruction that involves strong /isolated quad – esp 30-40 deg range (no open chain full ext)
- Co-contraction 30 and above no load to ACL
- HS action generally unloads ACL
- Femoral-on-tibia (CC) safer, HS co-contraction (squat)

BIOMECH SPRING - EXAM 2 (5 decks)

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