Patellofemoral joint stress Flashcards

1
Q

PFJ stress

A

incr. magnitude of PFJ > incr PFJ stress > dec. contact area

Even small decreases in body weight can substantially reduce PFJ load during functional activities

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2
Q

PFJ reaction force:

A

Quadriceps torque during functional activities:
Level walking = 0.5 x BW Stair climbing = 3-4 x BW
Squat = 7-8 x BW
May be magnified by patellar malalignment
PRESSURE = FORCE (BW) / AREA

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3
Q

Local Imparements

- quadriceps atrophy

A
  • Unilateral PFP (between-limb comparison):
  • meta-analysis: atrophy in PFP limb (thickness, CSA, volume)
  • VMO = VL
  • PFP vs. control participants:
    meta-analysis: atrophy in PFP
  • no difference in PFP vs. controls

Quadriceps atrophy may decrease VMO pennation angle and medial stabilising force

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4
Q

lower quadriceps strength in older adolescents & adults

A
  • age 12-15 years - no difference in isometric knee extension strength (males & females)
  • age 15-19 years - lower peak isometric quadriceps torque
    (females)
  • adults: lower quadriceps peak torque in PFP vs. unaffected limb (females) and compared to controls (males)
  • meta-analysis: lower knee extension peak torque is a risk factor for PFP
  • Quadriceps strength deficits may be present before PFP onset, and persist
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5
Q

altered quadriceps neuromuscular control

A

Vastus lateralis 12-15˚
Vastus medialis obliquus 5- 55˚
- Delayed onset of VMO vs VL was a risk factor for PFP
-Quadriceps dysfunction may be present before PFP onset, and persist

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6
Q

altered quadriceps neuromuscular control 2

A

Why is this important?
- significant increase in lateral PFJ load with 5ms VMO delay
- load more concentrated on lateral PFJ
- lateral patellar stress is associated with lateral patellar lesions,
and can be reduced by increased VMO activity
however A delay in VMO onset timing is not present in all people with PFP

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7
Q

local impairments - shorter hamstring length

A
  • people with PFP have shorter hamstrings compared to controls
  • people with reduced hamstring length have greater total and lateral PFJ stress during squat descent and ascent
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8
Q

local impairments - altered hamstring neuromuscular control

A
  • delayed onset of medial vs. lateral hamstrings during isometric hamstring contraction in
    PFP vs. controls
    mean difference 53.8ms
  • increased lateral hamstring and quadriceps activity during hop test in PFP vs controls
  • May increase pressure on the lateral patellar facet
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9
Q

local impairments

A
  • altered hamstring neuromuscular control
  • shorter hamstring length
  • altered quadriceps neuromuscular
  • quadriceps atrophy
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10
Q

Proximal Impairments - altered hip kinematics

A

greater hip adduction and IR during functional activities in PFP vs controls

(e. g. SL squat, stairs, hopping, running)
- Hip adductions and IR are predictors of pain and function
- hip IR and dynamic knee valgus during drop landing is a risk factor for PFP
- greater hip add. during running is a risk factor for PFP in female runner
* altered hip movement patterns may be present before PFP onset, and persist

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11
Q

altered hip kinematics

Why is this important?

A

in weight bearing, the femur IR under the patella

  • Non weight-bearing:
    Patellar tilt results from patellar rotation
  • Weight-bearing:
    Patellar tilt results from Internal femoral rotation
  • increased femoral IR (5-10°) during walking increases PFJ cartilage stress by ~30%
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12
Q

proximal impairments

- lower hip strength

A
  • moderate evidence of lower isometric strength in PFP vs controls (males & females)
  • moderate to strong evidence of no association between isometric hip strength & risk of PFP development
  • Deficits in isometric hip muscle strength may be a result of PFP, rather than a cause
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13
Q

proximal impairments

- altered gluteal neuromuscular control

A

Gmed delayed and shorter in duration during stair ascent, descent and running in PFP vs controls
- delayed GMed correlated with greater hip add. during running

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14
Q

proximal impairment

- lower isometric trunk strength

A

lower trunk isometric strength in PFP vs. controls

  • ext.
  • flx with rotation
  • side bridge
  • delayed onset of transversus abdominus and internal oblique in PFP vs controls
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15
Q

proximal impairments

A
  • lower hip strength
  • altered gluteal neuromuscular control
  • lower isometric trunk strength
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16
Q

distal impairments

greater foot pronation

A
  • people with PFP (vs. controls) have significantly greater: ankle dorsiflexion
  • calcaneal angle
  • navicular drop, navicular drift
  • Foot Posture Index
  • arch height mobility, foot mobility magnitude
  • greater navicular drop is a risk factor for PFP development
  • Greater foot pronation may be present before PFP onset, and persist
17
Q

greater rearfoot eversion during functional tasks

A
  • people with PFP (vs. controls) have significantly greater:
  • peak RF eversion during SL squat and stair ascent
  • peak RF eversion during SL triple hop
  • runners with PFP use a greater percentage of their available pronation ROM during running
  • peak RF eversion has a positive correlation with peak hip adduction in PFP and controls
  • Greater foot pronation may have implications for proximal control