The Knee: Anatomy and Injuries

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The Knee Anatomy and Injuries

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2 Joints at the Knee

• Tibiofemoral Joint formed between the femur
  (femoral condyles), and the tibial plateau
• A HINGE JOINT
• Patellofemoral joint formed between the patella
  and the femur
• A GLIDING JOINT

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Skeletal Anatomy

• Femur
• proximal head and neck of femur, greater
  trochanter
• distal medial and lateral
• condyles and epicondyles

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• Patella largest sesamoid bone in body
• Tibia tibial plateau forms knee joint with
  femur
• The fibula is not a part of the knee joint

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Muscles that move the knee and thigh

• The Quadriceps Knee Extension
• 1. Vastus Medialis
• 2. Vastus Lateralis
• 3. Vastus Intermedius
• 4. Rectus Femoris 2 joint muscle that
  also acts as a
• hip flexor

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• The Hamstrings- knee flexion
• 3 muscles
• 1. Biceps Femoris
• 2. Semimembranosus
• 3. Semitendinosus

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• The Adductors (Groin)
• Adduct the thigh
• 1. Adductor Longus
• 2. Adductor Magnus
• 3. Adductor Brevis
• 4. Gracilis

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• The Sartorius
• - flexes, abducts, and laterally rotates thigh
• - longest muscle in the body, tailors
  muscle
• - Crosses hip and knee joint

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• The Iliotibial Tract
• (IT Band)
• - neither a muscle or tendon, but a long,
  thick band of tissue that inserts into the
  lateral tibia (Gerdys Tubercle)

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The Major Knee Ligaments

• ACL Anterior Cruciate Ligament
• PCL Posterior Cruciate Ligament
• MCL Medial Collateral Ligament
• LCL Lateral Collateral Ligament

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The Cruciate LigamentsThe major stabilizing
ligaments of the knee

• ACL
• Runs from posterior femur to anterior tibia
• Prevents anterior displacement of tibia

• PCL
• Runs from anterior femur to posterior tibia
• Prevents posterior displacement of tibia

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The Collateral Ligaments

• MCL
• Medial Collateral Ligament
• Runs from medial femur to medial tibia
• Prevents valgus force

• LCL
• Lateral Collateral Ligament
• Runs from lateral femur to head of fibula
• Prevents varus force

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The Meniscus

• A c-shaped piece of fibrocartilage located in
  the knee joint between the femur and attached to
  the top of the tibia
• Cartilage meniscus

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Differences between medial and lateral

• Medial
• - larger and more C-shaped
• - more firmly attached to tibia
• - has attachments to MCL

• Lateral
• - smaller and more round or O-shaped
• - not firmly attached to tibia and LCL

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Blood Supply to the Meniscus

• Mostly avascular little or no blood supply
• Only the outer 20 has a blood supply
• Does not have the ability to heal itself unless
  there is a small tear in the outer 20

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Functions of Meniscus

1. Stability
2. Shock absorption
3. Lubrication and nutrition
4. Allows adequate weight distribution

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• Normal

• Torn

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Total Knee Joint Replacement

• Surgery to replace a painful damaged or diseased
  knee joint with an artificial joint (prosthesis)
• Artificial hip invented 1962
• 1969 first artificial knee in USA

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The Knee Surgery

• Thin layer of bone removed from femur thin
  metal replaces it
• Upper layer of tibia replaced with plastic
• Back of patella replaced with plastic
• Parts fastened with bone cement

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Risks of Knee Joint Replacement

• Blood clots in large veins
• Infection
• Stiffness
• Implant Loosening/Failure
• - more of a problem in younger patients

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Knee Injuries and Conditions

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• Genu Valgum
• knock knees

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• Genu Varum
• bowlegs

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• Genu Recurvatum
• hyperextension of the knee joint

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Patellar Tracking Disorder

• When your patella is out of balance or the
  patellar cartilage is damaged, you can have knee
  pain while climbing stairs, running, standing up
  from a bent-knee position, squatting, or even
  sitting for a period of time. This kind of pain,
  called anterior knee pain or patellofemoral pain
  syndrome, is sometimes caused by a common kneecap
  problem known as patellar tracking disorder.

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Causes

• Quadriceps weakness
• Tendon and muscle tightness in the leg, foot, or
  hip areas
• Improper athletic technique or training
• A blow to the kneecap
• Excessive body weight, which overstresses the
  knee joint.
• Genetics

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• Genetics (cont.)

- An excessively long patellar tendon - patellar
shape, hip structure, or a shallow femoral
groove for the patella to glide along
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Patellofemoral Disorders

• Problems with patella most common cause of knee
  pain
• Anatomy
• - Patella is a sesamoid bone formed in
  Quad tendon
• - Patellofemoral joint patella and femur
• - Compression forces
• ltbody weight during walking
• 2.5 x body weight during stairs

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Patellar Tendonitis

• Jumpers Knee
• Inflammation and degeneration of the tendon that
  connects the kneecap (Patella) to the shin bone
  (Tibia).

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Chondromalacia

• A gradual degenerative change that occurs beneath
  the patella
• Caused by acute trauma, repeated microtrauma, or
  improper alignment of the patella in the
  trochlear groove
• Weak vastus medialis (VMO) can cause improper
  alignment
• Prevention strengthen quads
• Minimize squats, downhill running, biking
  with low seat

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Chondromalacia

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Patellar Dislocation

• Dislocation usually occurs as a result of sudden
  direction changes while running and the knee is
  under stress or it may occur as a direct result
  of injury.
• Usually lateral

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• Rehab strengthen quads, especially VMO to hold
  patella in place
• Each dislocation will damage cartilage which can
  eventually lead to traumatic arthritis

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Osgood-Schlatter Disease

• 1. Painful swelling over tibial tuberosity
• (patellar tendon insertion)
• 2. Usually occurs between 9-13 years of age
• 3. Pain increases with activity

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• The Chopat Strap

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Iliotibial Band Friction Syndrome

• Occurs where IT Band rubs over femur at the knee
  joint
• Common in running (esp. downhill) or any activity
  with repetitive flexion
• Hills or stairs increase pain
• Lots of IT Band stretching

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Popliteal Cyst

• Bakers Cyst
• Fluid accumulation in posterior knee (popliteal
  space)
• Patient usually complains of a mass behind the
  knee

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Prepatellar Bursitis

• Housemaids Knee
• Tender swelling over the kneecap (prepatellar
  bursa)

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Pes Anserine Bursitis

• Pes anserine bursitis is an irritation or
  inflammation of a bursa in your knee. The pes
  anserine bursa is located on the inner side of
  the knee just below the knee joint.
• Tendons of three muscles attach to the shin bone
  (tibia) over this bursa

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Knee Sprains
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ACL Sprain

• Not most commonly torn knee ligament
• Higher incidence in females
• 2-8 times more likely
• Males contact
• Females noncontact

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ACL Sprain

• 1. MOI twisting of knee
• forced hyperextension
• lateral blow to knee
• foot must be firmly anchored to playing
  surface
• 2. May describe a pop in knee
• 35 - 65 of people
• 3. Knee fills with blood quickly
• Hemarthrosis
• 4. Usually immediate loss of motion
• 5. Knee feels unstable

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• Anterior Drawer Test
• examiner attempts to slide the tibia forward
  which may indicate a torn ACL ligament

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ACL Sprain

• Who needs surgery?
• - Activity level?
• - Level of Competition
• - Age?

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ACL Surgery

• Arthroscopic
• Graft options
• Patellar Tendon
• Semitendinosus
• Gracilis
• Cadaver
• Synthetic

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PCL Sprain

• MOI excessive hyperextension
• hyperflexion
• tibia forced posteriorly
• (blow to front of knee)
• dashboard knee
• Possibly 90 of all PCL injuries due to motor
  vehicle accidents?

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1. Mild hemarthrosis
2. Posterior knee pain
3. Walk with knee slightly flexed, avoid full
   extension
4. Posterior sag of tibia
5. Surgery?

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MCL Sprain

• MOI Blow to the outside of the knee Valgus
  Force
• Possible overuse breaststroke in
  swimmers
• Commonly associated with meniscal injuries
  attached to medial meniscus
• No surgery

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MCL Sprain
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• Valgus Stress Test
• tests for injury to the MCL ligament

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LCL Sprain

• MOI Blow to inside of the knee
• Varus force
• Grade III tear may require surgery

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• Varus Stress Test
• tests for injury to the LCL ligament

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Injuries to the Meniscus

1. MOI Rotation of the knee as the knee
   extends during rapid cutting or pivoting

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• Signs and Symptoms
• - pain
• - joint line tenderness
• - catching or locking
• - knee buckling or giving way
• - swelling
• - incomplete flexion
• - clicking on stair climbing

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• Surgery?
• Meniscectomy removal of the meniscus
• - Total meniscectomy osteoarthritis
• Depends on location of tear, type of tear,
  and blood supply

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Types of Meniscal Tears

• bucket handle
• Flap tear
• Transverse tear
• Horn tear

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Tests for Meniscal Tears

• Apleys Compression

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The Unhappy Triad

• Tear of the medial meniscus, anterior cruciate
  ligament (ACL), and medial collateral ligament
  (MCL)