Module 7 - Knee Injuries

Knee injuries comprise ~ 60% of all sport injuries

True

The lateral meniscus is more frequently injured than the medial due to it being more securely attached to the tibia (less mobile)

False, medial more injured

The suprapatellar bursae is the largest bursae in the body

True

Unhappy Triad

injury to the medial meniscus, ACL, and MCL

The medial tibial plateau is 50% larger than the lateral side

True

The lateral femoral condyle is larger than the medial condyle

False, medial is longer

Which femoral condyle is wider

lateral

Why is the medial tibial plateau larger than the lateral

to accommodate for the longer medial condyle

Tibio-femoral joint

• modified hinge joint (flexion and extension)

• when moving into full extension, the tibia rotates slightly laterally (sure home mechanism)

Superior tibio-fibular joint

• between lateral condyle of tibia and head of fibula

• connected by articular cartilage and anterior/posterior ligaments

Patella-femoral joint

• the patella serves to increase the angle of pull of the patella tendon

• improves mechanical advantage of quad muscle to produce extension

Function of the patella

• acts as a fulcrum

• helps change direction of quad and generates force throughout different joint angles

Viewed from above, the medial meniscus is semicircular, whereas the lateral meniscus is somewhat more circular

True

Meniscus

two fibrocartilaginous disks attached to the tibial plateaus

Functions of the meniscus

• stabilize joint by deepening articulation

• shock absorption

• provides lubrication and nourishment

• improve weight distribution

• assist ligaments and capsule in preventing knee hyperextension

How much of the meniscus is innervated? What does this do?

The outer third of each meniscus is innervated and contains nociceptors that send signals of pain to the brain when a meniscus is injured

The inner portion of the meniscus is more vascularized and has greater chance of healing than the avascular outer portion

False, outer more vascularized

Bursa

• fluid filled pillows throughout the body

• decrease friction and compression

Joint capsule in the knee

• thin articular capsule that is large and lax

• during flexion/extension, synovial fluid lubricates the knees articular surface

Bursas inside the knee joint capsule

• suprapatellar bursa

• sub-popliteal bursa (back side)

• semi-membranosus bursa (behind hamstring tendon)

Bursas outside of the knee joint capsule

• pre-patellar bursa (big one on top/front)

• superficial infrapatellar bursa

• deep infrapatellar bursa (back of patellar tendon)

Which bursa in the knee gets injured the most

pre-patellar bursa

Anterior Cruciate Ligament (ACL)

• critical stabilizer

• prevents anterior translation of the tibia on the femur

• prevents rotation of the tibia on the femur

• prevents hyperextension

ACL bands

• 2 bands

• Posterolateral bundle: taut in full extension

• Anteromedial bundle: taut in full flexion

Posterior Cruciate Ligament (PCL)

• critical stabilizer

• prevents posterior displacement of the tibia on the femur

The ACL is shorter and stronger than the ACL

False, PCL shorter/stronger

Primary stabilizer of the knee

PCL

PCL bands

• 2 bands

• Posterior Fibers: taut in full extension

• Anterior Fibers: taut in full flexion

ACL injury is more common than PCL injury

True

Medial Collateral Ligament (MCL)

• prevents medially directed shearing (valgus force)

• prevents rotational force

MCL layers

• 2 layers (superficial and deep)

• all fibers = taut in full extension

• Posterior fibers= taut in midrange flexion

• Anterior fibers= taut in flexion

Lateral Collateral Ligament (LCL)

• prevents laterally directed shearing (varus force)

• prevents external rotation of the tibia on the femur

TFL origin

anterior iliac crest and ASIS

TFL insertion

into IT band tract 1/3 down the thigh

TFL action

• hip flexion

• hip abduction

• internal rotation

Sartorius origin

anterior iliac spine (ASIS)

Sartorius insertion

medial tibia

Sartorius action

• hip flexion

• hip abduction

• lateral rotation

What muscle allows our leg to go into the figure-4 position

sartorius

IT band function

• transmits forces

• acts as an insertion point

• lateral knee stabilizer

Quadricep femoris insertion

common tendon to the patella

Quadricep femoris action

• hip flexion (rectus femoris)

• knee extension

Rectus femoris origin

anterior inferior iliac spine (AIIS)

Vastus lateralis origin

anterior inferior border of greater trochanter

Vastus medialis origin

intertrochanteric spine

Vastus intermedius origin

upper 2/3 of anterior/lateral femur

Bicep femoris origin

• short head: linea aspera

• long head: ischial tuberosity

Bicep femoris insertion

lateral head of fibula

Bicep femoris action

• knee flexion

• weak hip extension (long head)

Semi-membranosus origin

ischial tuberosity

Semi-membranosus insertion

posterior/medial tibial condyle

Semi-membranosus action

• knee flexion

• weak hip extension

Semi-tendinosus origin

ischial tuberosity

Semi-tendinosus insertion

anterior surface of tibia

Semi-tendinosus action

• knee flexion

• weak hip extension

Pes anserine

• tripod that creates stability through the antero-medial and postero-medial aspect of the knee

• common attachment of semitendinosus, sartorius, and gracilis

Pes anserine action

• knee flexion

• rotate lower leg internal rotation

• help stabilize inside of knee joint

Pes anserine bursa

• located between the three tendons and tibia

• purpose is to decrease friction

• can become inflamed with too much compression

Gracilis origin

body of pubis near symphysis and inferior ramus

Gracilis insertion

upper medial surface of tibia

Gracilis action

hip adduction

IT band origin

• iliac crest

• ASIS

• TFL

• glute max

IT band insertion

gerdy tubercle on lateral tibial plateau

WB and tension from muscles crossing the knee contribute to increased compression and shear

True

In full flexion, there is increased compression on the knee

False, full extension

What compartment of the knee sustains the majority of the load during stance

medial

Major vascular structures

• femoral artery

• popliteal artery

• medial and lateral superior genicular

• middle genicular

• medial and lateral inferior genicular

Major nerves

• anterior: femoral

• posterior: sciatic

  • tibial

    • sural

  • common peroneal

    • deep and superficial peronial

Ottawa Knee Rules

x-ray is necessary if nay of the following are met:

• 55 years or older

• isolated tenderness of patella

• tenderness at head of fibula

• inability to flex knee to 90 degrees

• inability to weight bear

Potential cause of suprapatellar swelling

• suprapatellar bursitis (quad involvement)

• if more lateral, internal derangement including articular cartilage damage

Potential cause of anterior/around patella swelling

• prepatellar bursa

• patellofemoral dysfunction

Potential cause of distal patella swelling

• fat pad contusion

• internal derangement including articular cartilage damage

Potential cause of popliteal space swelling

• Baker’s cyst

• internal derangement including articular cartilage damage

• gastrocnemius strain

• deep vein thrombosis

Potential cause of medial knee swelling

• MCL

• medial meniscus

• pes anserine buritis

• tendinitis

Potential cause of lateral knee swelling

• LCL

• lateral meniscus

• ITB compression

Knee contusion MOI

• compressive forces

• direct force

• falling onto knee

Knee contusion S+S

• localized TOP

• pain

• swelling

• ecchymosis

• if fat pad: locking, catching, giving way

• if acute nerve: immediate ‘shock’, numbness, tingling

• severe nerve injury: muscle weakness

Injured structures in knee contusion

• infra patellar fat pad

• common peroneal nerve

Acute management for knee contusion

• NSAID

• PRICE (restricted movement)

• protect area if returning to activity

• if changes in sensory/motor weakness arise = refer

What situations are knee contusion commonly seen in

• soccer

• baseball

• softball

Recovery timeline for knee contusion

• based on severity

• 2+ weeks to months

RTS considerations for knee contusion

• may not be limited

• participate within pain tolerance

• knee pads/bracing

S+S of minimal ligament failure

• less than 1/3 pf fibers torn

• mild swelling and pain localized over injury site

• active and passive ROM normal

• muscular strength normal or slightly decreased

• no joint laxity

• definite end feel present

S+S of partial ligament failure

• 1/3 to 2/3 of ligament damaged with micro tears present

• localized swelling/joint effusion may result from deep capsular tears, meniscus damage, or cruciate ligament damage

• pain is sharp (transient or lasting)

• instability and inability to walk with heel on ground

• ROM decreased initially by pain and later swelling/effusion

• inability to fully extend actively

• visible translation of tibia during stress test

S+S of complete ligament failure

• more than 2/3 of ligament ruptured

• swelling it diffuse (indicating severe capsular tear and damage to intracapsular structures)

• pain initially sharp and disappears within one minute

• patient aware of instability of knee giving way

• significant loss of ROM

• visible distraction of greater than 10mm during stress testing (may appear as subluxation)

MCL injury MOI

• valgus force

• often in WB or closed kinetic position

Injured structures in MCL injury

• MCL

• possibly medial capsular ligaments and ACL

S+S of grade 1 MCL injury

• mild TOP over MCL

• full ROM

• mild pain

• stable joint with stress testing

S+S of grade 2 MCL injury

• mild to moderate joint effusion

• lacking full extension

• antalgic gait

• increased tenderness over MCL

• pain and mild laxity with stress testing

S+S of grade 3 MCL injury

• loss of ROM

• TOP of MCL

• significant joint laxity with stress testing

• may have minimal effusion

• sense of instability into knee

• may also have meniscal + ACL pathology

Acute mangement for MCL injury

• PRICE (splint to immobilize)

• crutches if needed

• refer to medical professional to properly diagnose/refer for imaging

What situations are MCL injury commonly seen in

• football

• basketball

• rugby

• skiing

Recovery timeline for MCL injury

• based on severity

• 3-12 weeks+

RTS considerations for MCL injury

• proprioceptive bracing

• rotary and valgus knee control

LCL injury MOI

• varus force

• often in WB of closed kinetic position

Injured structures in LCL injury

• LCL

• possibly postero-lateral capsular ligaments and PCL

Acute management of LCL injury

• PRICE (splint to immobilize)

• crutches if needed

• refer to medial professional to properly diagnose/refer for imaging

What situations are LCL injury common seen

• football

• basketball

• rugby

• skiing

• wrestling

Recovery timeline for LCL injury

• based on severity

• 3-12 weeks+

RTS considerations for LCL injury

• proprioceptive bracing