The Knee

What are the arthrokinematics at the hip, knee, and ankle? - stand to sit

Hip = anterior roll and anterior glide • anterior pelvic tilt hip, pelvis on femur. • concave on convex Knee = posterior roll and anterior glide • flexing at knee; femur on tibia movement • femur moves behind frontal plane Ankle = anterior roll and glide • tibia anterior roll of tibia on talus. • concave on convex

What are the arthrokinematics of hip adduction in CKC?

Inferior roll and glide o Acetabulum moving on femur o Acetabulum moves inferior, femur moves superior

LCL Fibular Collateral Ligament

1.Resists varus (adduction) 2.Resists extension 3.Resists extremes of rotation

ACL injury: non-contact ACL injury

1.Strong quad activation over moderately flexed or nearly extended knee 2.Marked valgus collapse of the knee 3.Excessive external rotation of the knee (femoral IR on fixed tibia)

Describe: Patellofemoral joint congruency

135 degrees of flexion •Patella contacts femur near superior pole •Patella rests well below the trochlear groove •Lateral edge of lateral facet and the "odd" facet contact the femur 90 degrees of flexion •Patella contacts femur toward its inferior pole •90-60 degrees of flexion = good congruency (greatest contact area) of patella in intertrochlear groove (PFP) • 20 degrees of flexion •Patella contacts femur at its inferior pole •Patella loses mechanical engagement with the trochlear groove • Full extension •Patella rests completely proximal to intertrochlear groove and against suprapatellar fat pad •Typically where lateral dislocations occur - joint congruency is lost

Synovial membrane and bursae how many bursae?

14

How many degrees of genu valgum is normal?

5-10

The knee: Closed Packed Position and Resting Position

Closed Packed Position •Maximal knee extension Resting Position •25 to 40◦ flexion

PCL: O and I

O: Posterior intercondylar area of tibial plateau I: lateral side of medial femoral condyle (direction of fibers from O to I = anterior, superior, medial)

ACL: O and I

O: anterior intercondylar area of tibial plateau I: medial side of lateral femoral condyle (direction of fibers from O to I = posterior, superior, lateral)

T/F: This external rotation is not an independent movement, but occurs in conjunction with the extension

True

The Evolute

axis of rotation migrates w a little bit of mvt.

How would you describe the muscle activity at the hip knee, and ankle? - sit to stand

concentrically Hip: glutes and proximal hamstrings Knee: quads Ankle: not much muscle activation here, ankle s just coming up here (compared to stand to sit)

How would you describe the muscle activity at the hip knee, and ankle? - stand to sit

eccentrically Hip: glutes and proximal hamstrings Knee: quads Ankle: gastric and soleus

Does Posterior pelvic tilt increase or decrease hip flexion?

increase hip extension

Does Anterior pelvic tilt increase or decrease hip flexion?

increase hip flexion

During flexion, the knee must 1st internally rotate to unlock...what muscle is responsible for this action?

popliteus

Fill in the blank: In standing, the apex of the patella lies just _________ to the knee joint line

proximal

Describe how the external moment arm works throughout knee flexion and extension in OKC

• A: - looking at where external force is coming from - everything is in line, coming from joint line no external moment arm - lower impact on the knee joint, quad has minimal work here • B: - external moment arm is present - arm shifted distally, not in line with axis of rotation - increased stress, quad works harder to overcome force - More compressive force on knee jt. • C: - Longer moment arm, quad works hard, tibiofemoral and patellofemoral stress high!! - Most amount of stress on the knee jt.

quadriceps action at the knee

• External flexor torque (gravity + weight of limb) is acting at the knee • External Torque = external load x external moment arm

Patellar tracking

• Most important influencer in patellar biomechanics is the magnitude and direction of the force produced by the quadriceps • Normal biomechanics includes superior with slight lateral and posterior movement (knee flexion, JFR)

Normal Q angle

• Normal Q-angle = 13-15 degrees • The larger the Q-angle, the greater the lateral muscle pull on the patella • Clinical implication of lateral tracking (problematic) • PFP • Subluxation • Dislocation

Q-Angle

• Quadriceps Angle (Q-angle) is a clinical measure of the overall lateral line of pull of the quadriceps relative to the patella

In terms of muscle contraction: describe concentric and eccentric muscle action on the knee

- Concentric muscle activation = knee extension works hardest with this (increase stress/force at the knee) - Eccentric muscle activation = knee flexion work hardest with this (increase stress/force at the knee)

PCL Mechanism of injury

Associated with high-energy trauma (3 ways to injure) •MVA - "dashboard injury" •Football •Falling on a flexed knee

Patellofemoral Joint: describe the compression forces and JRF

Exposed to high magnitudes of compression forces Joint reaction force gets longer as we go further into knee flexion, higher compressive forces at patellofemoral jt. • 1.3 times body weight during walking on level surfaces • 2.6 times body weight during SLR • 3.3 times body weight during ascending stairs • 7.8 times body weight during deep squatting

Describe how the external moment arm works throughout knee flexion and extension in CKC

Further in knee flexion, quads work harder, more stress on knee jt. (tibiofemoral and patellofemoral) Example: returning soccer players need to be trained where quad stress is HIGH (position C of top image), opposite for dancer who has weak quads train them in position where quad stress in LOW (position D for bottom image)

What are the arthrokinematics at the hip, knee, and ankle? - sit to stand

Hip = posterior roll and posterior glide • pelvis on femur moving • posterior pelvic tilt • acetabulum on head of femur movement Knee = anterior roll and posterior glide • femur on anterior direction movement • Closer to frontal plane Ankle = posterior roll and posterior glide • mortise on talus movement, tibia moves posterior

What osteokinematic motions are occurring at the hip, knee, ankle? - sit to stand

Hip: extension Knee: extension Ankle: PF

What osteokinematic motions are occurring at the hip, knee, ankle? - stand to sit

Hip: flexion Knee: Flexion Ankle: DF

Why are these 3 things clinically significant? •Several muscles have attachments to the menisci •External 1/3 of menisci receives a direct source of blood •Inner 2/3 of menisci essentially avascular

Inner cannot repair itself (debridement) Outer can repair due to sufficient blood supply Muscle attachments Both should be assessed and considered when working on interventions

Tibiofemoral Internal and external rotation

Knee fully extended = little to no rotation Greater knee flexion = greater rotation Knee flexed to 90 degrees = 40 to 45 degrees of rotation External rotation > internal rotation by 2:1 ratio

Meniscal tears are the most common injury at the knee Is medial or lateral more common?

Medial > lateral •Meniscal tears occur most commonly with a rotation about a flexed knee in weight bearing

Varus force

Primary Restraint = LCL Secondary Restraints •Posterior-lateral capsule •IT Band •Biceps femoris tendon •Joint contact medially •Compression of the medial meniscus •ACL and PCL •Gastrocnemius (lateral head)

Valgus force

Primary Restraint = MCL •Superficial fibers with knee flexed 20-30 degrees •Deep fibers with knee in full extension Secondary Restraints •Posterior-medial capsule •ACL and PCL •Joint contact laterally •Compression of the lateral meniscus •Medial retinacular fibers •Pes Anserinus Gastrocnemius (medial head)

Trendelenburg Sign

Single leg stance hip drop = Adduction • Taking the Trendelenburg sign, a step further • Hip add = medial knee pain or valgus force • IR of femur can be seen sometimes, puts you in even more of valgus and pronation of foot o Flatter foot placement on the ground posterior tib tendinitis/shin splints, plantar fasciitis, lateral ankle pain from compressive forces)

Genu Valgum: LE Clinical Implications

• Structural increase in genu valgum: lengthened MCL • Momentary increase in genu valgum: lengthened MCL • Purpose is to assess not just medial side but lateral too due to compression • Femur is ADD, ADDuctors are constantly ON and lengthened o Mechanically disadvantaged, so hard to keep hips level • Tibia ABD, excessive pronation, flat foot

Clinical Application

• minimize likelihood to increase symptoms • put them in positions in relation to this • when they are stronger, we can put them in full extension on close to it

Shaft of femur has a slightly medial orientation as it descends toward the knee, what does this result in?

•125 degree angle of inclination (neck and shaft angle)

Excessive Genu Valgum

•< 170 degrees •"knock-knee" •Knees too close together Must fcn at this: Increased passive tension •Increased tension on medial structures of the knee

Genu Varum

•> 180 degrees •"bow-leg" •Increased stress on lateral knee LCL IT band , lateral hamstring vastus lateralis

MCL

•Attach directly to the joint capsule, medial meniscus, and tendon of semimembranosus (Injury to MCL, MUST assess all of these) Functions: 1.Resists valgus (abduction) 2.Resists extension 3.Resists extremes of rotation

Tibiofemoral joint

•Biaxial •Modified-Hinge: sagittal plane w flexion and extension •Some frontal plane motion •2 degrees of freedom •F/E, IR, ER

ACL Mechanisms of injury

•Excessive hyperextension with planted foot •70% of sporting ACL injuries are non-contact or minimal contact injuries •Landing from a jump •Quick and forceful deceleration •Cutting •Pivoting over a fixed LE

"Screw-Home" Rotation of the Knee

•External rotation of the knee that occurs during the last 30 degrees of extension •Locking the knee in full extension requires about 10 degrees of external rotation at the knee

Patellofemoral joint

•Interface between patella and trochlear groove of femur •Glides •Superior/inferior •Medial/lateral

Cruciate ligaments

•Intracapsular •Poorly vascularized •Provide stability to the knee •resist extremes of ALL knee movements

Primary and Secondary functions of menisci

•Primary function: Reduce compressive stress across the tibiofemoral joint Secondary functions: •Stabilizing the tibiofemoral joint during movement •Lubricating the articular cartilage •Providing proprioception •Guiding the arthrokinematics

Lateral Collateral Ligament (LCL)

•Primary restraint to lateral gapping or varus force

Medial Collateral Ligament (MCL)

•Primary restraint to medial gapping or valgus force

Anterior Cruciate Ligament (ACL) function

•Restrains anterior tibial translation on the femur and IR of the tibia on the femur •tibia moving on femur

Posterior Cruciate Ligament (PCL)

•Restrains posterior tibial translation on the femur •tibia moving on femur

"Screw-Home" Rotation of the Knee Driven by 3 factors

•Shape of the medial femoral condyle* •Passive tension in the ACL •Slight lateral pull of the quadricep muscle

PCL

•Type I collagen •Aides in limiting posterior tibial translation (glide) during flexion •Counteracts the external force of the hamstrings in this range of motion •Aides in limiting anterior translation of the femur during closed chain activities

ACL

•Type I collagen •Taught in max extension •Extension > 0◦ = further elongation of the ACL •Tearing occurs •Aides in limiting anterior tibial translation (glide) during last 50-60 degrees of knee extension (going into full extension) ACL and quads fight against each other ACL and hammies work together