Jenny Kempf, MPT

Review epidemiology of knee pain

Discuss etiology and the biomechanics of knee pain utilizing current literature/evidence

Review commonly seen knee injuries

Discuss treatment strategies

Approximately 85% of all recreational cyclist sustain an injury60% of cycling injuries occur in the knee

Anterior knee painPatellar tendonitis

Overuse injuries most common, traumatic event second

Improper trainingImproper bike fit

Cycling is a repetitive activity1 hour = 5400 pedal revolutionsCan result in microtrauma or overuse injuriesKnee most common location or overuse injury

Training errorBike fitPedaling mechanics/TechniqueMuscular imbalances

NOVICE ELITE

Greater variability b/npedal strokesGreater variability b/nridersGreater amplitude of muscle activityGreater amplitude and duration of muscle activity↓ coordination of sagittal plane motion

Consistent patterned movements at hip and kneeGreater ankle ROM throughout pedal cycleLess motion in frontal and transverse plane at knee

Chapman et al. J Sci Med Sport 2009

Too muchToo soonSo wrong

Why is knee pain so prevalent in cyclists?

Low level repetitive loading Bike fit

Bike anatomyRider anatomy

Driving moments – muscle forces

Non driving moments – varus/valgus, internal/external axial

CommercializedStandardizedDynamic?Individualized?

Patellofemoral painCompression forceShear force

Patellar tendon pain

Iliotibial band syndrome

24 cyclist (14 no injury hx/10 injury hx)Video analysis of frontal and sagittal planesMeasured shank (tibia compared to ankle) angleComparison of groups

Bailey et al. J Sports Sci. 2003

NO INJURY GROUP INJURY GROUP

Mean shank angle neutralSpeed of frontal plane mvmt same Greatest shank abduction - 83º

Mean shank angle in abductionGreatest shank abduction - 88ºIncreased DF angle throughout pedal cycle

Bailey et al. J Sports Sci. 2003

24 cyclist (14 no injury/10 injury)Video analysis of frontal and sagittal planesMeasured knee flexion anglesComparison of groups

Found no differences in knee flexion anglesDoes not support low saddle height increases risk of knee injury!

Bailey et al. J Sports Sci. 2003

8 cadaver legsTested at 60º and 90º knee flexion3 loads placed

Internal moment (femur)Varus moment (tibia)Combined

Measured patellofemoral jointContact areaContact pressure

Wolchok, Howell. J Biomech

1998

ResultsInternal knee moments and combined moments significantly increased mean contact area and force to patellaContact area appeared more sensitive to the internal than varus momentNo effect on mean contact pressure

Wolchok, Howell. J Biomech

1998

11 healthy subjects3 different riding positions

NaturalDorsiflexedPlantarflexed

Measured muscle activity and efficiency

Cannon et al. Eur J Appl Physiol. 2007

Found DF riding position increased gastroc activity and increased energy expenditurePF riding position increased biceps femoris activity

DF riding position places eccentric load to gastroc which may absorb energy produced at kneeEliminating DF during power phase may reduce muscle fatigue and maximize load placed through the pedal

Cannon et al. Eur J Appl Physiol. 2007

15 subjects with varying foot angle positions on pedal

10º inverted5º invertedNeutral10º everted5º everted

Measured varus/valgus and internal/external knee moments

Gregersen

et al. J Biomech

Eng. 2006

ResultsPeak varus and average varus/valgus knee moments are related to foot angleFoot eversion decreased both varus moment during power stroke

Gregersen

et al. J Biomech

Eng. 2006

Based on research - Control the frontal planeReduce medial knee positioning (shank abduction)

FitRiding TechniqueStrength

Pedal widthFoot position

FloatCant

Seat height

Optimal cadence = 88-95+ rpmSpinners – low gear, high cadence

Gear Mashers – high gear, low cadence… increased risk of knee injury in this group

Use entire pedal cycle

Toe down

Clock Analogy1-10 – rolling barrel with bottom of foot. Push pedal forward over top of apex10-7 – push down, easiest and most natural position7- 5 – scraping mud off bottom of shoe5-1 – “de-weight” the pedal

Cadence WorkEasiest way to smooth out pedal inefficiencies is to increase cadence = neuromuscular re -educationKeep toe down, NO bouncing in the saddle“Spin ups”

Lower resistance pedal until you just start to bounce in saddle. Back off rpm slightly or control buttocks

ProgressionsChange in rpm without change in resistance

Isolated Leg Drills

Resistance is key – should be easy to keep high cadence, hard so pelvis isn’t bouncing

Right leg over barrelLeft leg over barrelRight leg scrap mudLeft leg scrap mud