The Knee Complex The Knee Complex A B

The Knee Complex

The Knee Complex A. B. C. General Structure & Function of Specific Joints Muscular Considerations

General Structure

Joints of the Knee Complex

General Function l l Provides very mobile link in an otherwise stable lower extremity Transmits loads from tibia/fibula to femur

Knee Complex Movements

Sagittal plane • Flexion, extension Transverse plane • Medial and lateral rotation

Knee Complex Movements l Frontal plane l l l Varus, valgus Anteroposterior translation Mediolateral translation

The Knee Complex A. B. C. General Structure & Function of Specific Joints Muscular Considerations

Structure & Function of Specific Joints 1. 2. 3. Tibiofibular Joint Patellofemoral Joint Tibiofemoral Joint

Tibiofibular Joint: Bony Structure Amphiarthrodial membranous syndesmosis joint

Structure & Function of Specific Joints 1. 2. 3. Tibiofibular Joint Patellofemoral Joint Tibiofemoral Joint

Purpose of Patella l l l Increase leverage of QF Protect joint during knee flexion ↓ pressure and distribute forces on femur Prevent Fcompression on PT in resisted knee flexion Disadvantage: ANT shear of QF

Patella Structure l l l Medial facet Lateral facet Odd facet (30%) M L

PF Articular Surfaces l l l Largest sesamoid bone Least congruent joint Articular cartilage Vertical ridge Facets M L

PF Articular Surfaces l l l Largest sesamoid bone Least congruent joint Articular cartilage Vertical ridge Facets Angle of femoral sulcus

Patellar Motion l l INF & SUP Sliding Patellar tilt l 11 MT as KN FL Lat Med

Patellar Motion l Lateral rotation l l l ACC MR of femur 6 through KN FL Medial rotation l ACC LR of femur

Patellalectomy l l ↓ MA of QF (↓ strength 49%) Q tendon friction compressive stress on groove by Q tendon Most evident in closed chain EXT l l l ECC QF in CC Coupled w/ & assisted by hip & ankle movement QF not needed in erect posture of CC

Extension Little effect overall

Slight Flexion Noticeable weakness

Extreme Flexion Noticeable weakness

From 0° to 60° of Knee Flexion

l l l 0 -60 Contact area MA of QF; 60 ANT shear of QF l 0 -60 Facet contact at 20

From 60° to 140° of Knee Flexion

l l l 60 -140 contact area MA of QF No leverage in full FL

l l Overall Medial facet most contact Odd facet least contact

During Full Extension l l l Full EXT MA of QF length Patella very unstable

PF JRF l l Amount of knee FL Strength of QF contraction

PF Compressive Forces Descending stairs Max isometric extension Kicking Parallel squat Isokinetic knee extension Rising from chair Running/jogging Ascending stairs Walking Cycling 4000 N 6100 N 6800 N 14, 900 N (7 -8 X BW) 8300 N 3800 N 5000 N (3 -4 X BW) 1400 N 840 -850 N (0. 5 -1. 5 X BW) 880 N

Compensatory Mechanisms for Compressive Force Distribution l l Contact area with knee flexion Medial facet contact from 30 -70 l Thickest hyaline cartilage in body

Compensatory Mechanisms for Compressive Force Distribution l l Contact area with knee flexion Medial facet contact from 30 -70 l l Largest QF MA 30 -70 l l Thickest hyaline cartilage in body QF torque as MA decreases QF tendon contacts condyles 70 -90

Normal Patella Tracking l l l Maintains maximum congruence Passive restraints Active restraints

Abnormal Patella Tracking l l l ↓ congruence Stretches capsule & retinacula ↓ contact area Lateral Medial

Causes of Abnormal Tracking l l Skeletal abnormalities Strength imbalance in QF Strength imbalance in fibrous tissues Compensatory movements in knee due to abnormal foot movement

Skeletal Abnormalities: Q-angle

Skeletal Abnormalities: Genu Varum & Genu Valgum l l Q angle w/ age Varum common in very young children Valgum seen in growing children Menisectomy effects

Skeletal Abnormalities: Patella Alta & Patella Baja l Index of Insall & Salviti l l l LT/LP Normal = 1. 0 Patella alta = 0. 8 Patella baja = 1. 2 Women ratio

Skeletal Abnormalities: Patella Surface Lateral Border l l l Appositional forces ↓ in full extension Prominence of lateral border prevents lateral displacement Underdevelopment common in children as growing

Skeletal Abnormalities: Femoral & Tibial Torsion l Lateral tracking

Causes of Abnormal Tracking l l Skeletal abnormalities Strength imbalance in QF Strength imbalance in fibrous tissues Compensatory movements in knee due to abnormal foot movement

QF Strength Imbalance

Causes of Abnormal Tracking l l Skeletal abnormalities Strength imbalance in QF Strength imbalance in fibrous tissues Compensatory movements in knee due to abnormal foot movement

Fibrous Tissue Strength Imbalance IT

Causes of Abnormal Tracking l l Skeletal abnormalities Strength imbalance in QF Strength imbalance in fibrous tissues Compensatory movements in knee due to abnormal foot movement

Compensatory Movement l l l Pronation of foot accompanied by medial rotation of tibia medial rotation & medial translation of patella Pronation coupled w/ forceful quadriceps femoris leads to anterior tilt EX: jumping, landing, running

Summary