Patellofemoral joint stress Flashcards
PFJ stress
incr. magnitude of PFJ > incr PFJ stress > dec. contact area
Even small decreases in body weight can substantially reduce PFJ load during functional activities
PFJ reaction force:
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
Local Imparements
- quadriceps atrophy
- 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
lower quadriceps strength in older adolescents & adults
- 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
altered quadriceps neuromuscular control
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
altered quadriceps neuromuscular control 2
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
local impairments - shorter hamstring length
- 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
local impairments - altered hamstring neuromuscular control
- 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
local impairments
- altered hamstring neuromuscular control
- shorter hamstring length
- altered quadriceps neuromuscular
- quadriceps atrophy
Proximal Impairments - altered hip kinematics
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
altered hip kinematics
Why is this important?
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%
proximal impairments
- lower hip strength
- 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
proximal impairments
- altered gluteal neuromuscular control
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
proximal impairment
- lower isometric trunk strength
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
proximal impairments
- lower hip strength
- altered gluteal neuromuscular control
- lower isometric trunk strength