Exam 2 Learning Objectives Flashcards
Active Insufficiency
Occurs when a multi-joint muscle reaches a length (shortened) where it can no longer apply an effective force
Passive Insufficiency
Refers to inability of a multi-joint muscle to lengthen to a degree that allows full range of motion of all the joints it crosses simultaneously
Normal ROM for the Knee
Flexion
- Active ROM (Hip Extended) → 120 degrees
- Active ROM (Hip Flexed) → 140 degrees
- Passive ROM → 160
Extension
- Active/Passive ROM → -5 to 10 degrees
Rotation and Add/Abduction
- At 0 degrees flexion (full extension) → no frontal or transverse plane movement
- At 30 degrees flexion → mild frontal plane motion (abd/add)
- At 90 degrees → max transverse plane motion
- ER in 90 degrees flexion → up to 45 degrees
- IR in 90 degrees flexion → up to 40 degrees
Describe the anatomical differences between femoral condyles and what they effect regarding knee function
Medial femoral condyle is wider than the anterior condyle (Ant to Post)
- Aids in screw home mechanism
Medial femoral condyle projects further distally
- Generates genu valgus
- 1.7 cm longer than lateral on average
Lateral femoral condyle projects further anterior than the medial condyle
- Creates patellar buttress
Tibial plateau has a 5-10 degree posterior slope
Medial Meniscus
- C-shaped
- Attached to the MCL
- Posterior horn is attached to the semimembranosus via the capsule
Lateral Meniscus
- O-shaped
- More mobile
- Does not attach to collateral or capsular ligaments
- Attaches to the arcuate ligament and popliteus muscle
Function of the Meniscus
- Absorb and distribute compression forces
- Facilitate proper motion (center pathway)
- Aid in nutrition of joint
- Aids joint stability facilitated by menisci by making the tibia more concave
Load-Bearing Properties of the Meniscus
- Menisci carry up to 70% of the load on the tibia
- 3x greater stress on tibia w/o the menisci
- Forces centralize on the tibia without the menisci instead of being radially directed
Movement of the Meniscus
Menisci move with tibia during flexion/extension (direction of glide)
- Flexion → menisci move posteriorly
- Extension → menisci move anteriorly
Move with the femur during rotation
Lateral meniscus moves ~2x as much as the medial (15-20 mm)
Types of Meniscal Tears
- Longitudinal
- Bucket handle
- Flap
- Transverse
- Torn Horn
Signs/Symptoms of Meniscal Injury
- Joint line pain
- Loss of flexion (> 10 degrees)
- Loss of extension (> 5 degrees)
- Swelling (synovial)
- Crepitus
- Positive special test (see below)
Tests for Meniscal Injury
- Apley’s Compression/Distraction
- McMurray’s Test
- Bounce Home Test
ACL
- 2 bundles ~ Anteromedial bundle tighter in flexion ~ Posterolateral tighter in extension - Handles up to 75% of anterior tibial force when knee is at full extension - Handles up to 90% of anterior tibial force when knee is flexed - Checks ~ Anterior tibial shear ~ IR of the femur ~ ER of the tibia - Special Tests ~ Lachman’s Test ~ Anterior Drawer Test ~ Pivot Shift Test
PCL
- Handles b/t 85 and 100% of posterior tibial force at both 30 and 90 degrees of flexion
- Checks
~ Posterior tibial shear
~ Special Tests
~ Sag Test
~ Posterior Drawer Test
MCL
- Handles up to 50% of the valgus force on the knee
- Checks
~ Tibial abduction (valgus force)
~ ER of tibia - Special Tests
~ Valgus Stress Test
LCL
- Handles ~55% of varus force at full extension and increases with flexion
- Checks
~ Tibial adduction (varus force)
~ IR of tibia - Special Tests
~ Varus Stress Test
Anterior Bursae of the Knee
- Suprapatellar
- Prepatellar (most problematic)
- Subcutaneous infrapatellar
- Deep infrapatellar
Posterior Bursae of the Knee
- Popliteus
- Semimembranosus
- Gastrocnemius
Medial Bursa of the Knee
Pes Anserine
Transverse Ligament
- AKA anterior meniscofemoral ligament
- Helps prevent anterior horns of menisci from moving forward
Coronary Ligament
- AKA meniscotibial ligament
- Blends with joint capsule but hold meniscus down to periphery of tibia
Function of the Patella
- Aids in knee extension by anteriorly displacing the quadriceps tendon (lengthens the lever arm)
- Allows wider distribution of compressive forces on femur by increasing area of contact with patellar tendon
Influence of the Patella on the Lever Arm
- Full flexion- little anterior displacement (small lever arm) → force is the least
- Lever arm rapidly increases (30% in length) during knee extension up to 45 degrees
- Lever arm actually decreases slightly after 45 degrees, requiring more quad force to finish extension → up to 60% more
What would happen if there were no patella?
- No knee cap = small force arm since tendon is closer to the groove
- Without a kneecap, full ROM of knee extension will require at least 30% more quad force
Parts of the patella that are in contact with the femur during movement
-
Patella Baja
-
Patella Alta
-
Insall Ratio
-
Muscle-Tendon Units and Knee Support
-
Lower Extremity Tests
-
Periods of the Gait Cycle
Stance - 60% of the cycle - Foot is in contact with the floor Swing - 40% of the cycle - Foot is off the ground
Phases of the Gait Cycle
- Initial contact
- Loading Response
- Mid stance
- Terminal stance
- Pre swing
- Initial swing
- Mid swing
- Terminal swing
Initial Contact
- Initial contact of right heel
- Period of double limb support
Loading Response
- Shock absorption with knee flexion
- Foot flat
- Continued phase of double limb support
Mid stance
- End of mid stance when swing limb tibia is vertical
- Body weight shifts towards forefoot on stance limb
Terminal stance
- Still period of single limb support
- When body weight moves ahead of forefoot
Pre swing
- Initial contact of left foot
- Period of double limb support during pre-swing
Initial swing
-
Mid swing
-
Terminal swing
-
Step length
Initial contact of one lower extremity to initial contact of other lower extremity
Stride length
Initial contact of one lower extremity to initial contact of the same lower extremity
Double support
- Time in which both feet are in contact with the ground
- Makes up about 22% of the gait cycle
Width of base of support
Typically 1-5 inches
Toe out
Average of 4-7 degrees
Cadence
Number of steps a person will take per unit of time
Functional role of lower limb during the stance phase
Support, propulsion, balance, force absorption
Functional role of lower limbs during the swing phase
Toe clearance, foot trajectory and placement
What’s the normal range for measurement in Craig’s test?
- Can give a generalized measurement of hip anteversion
- 8-15 degrees of medial rotation is normal
What’s the natural progression of limb alignment from infancy to 7 years of age?
- Infant = varus
- 18 months = neutral
- 3.5 years = valgus
- 7 years = neutral
