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The Knee: Anatomy and Injuries
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2 Joints at the Knee Tibiofemoral Joint – formed between tibia and femur 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, “tailor’s 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 (Gerdy’s Tubercle)
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What muscles can you identify?
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The Major Knee Ligaments
1. ACL – Anterior Cruciate Ligament prevents anterior motion of tibia 2. PCL – Posterior Cruciate Ligament prevents posterior motion of tibia 3. MCL – Medial Collateral Ligament 4. LCL – Lateral Collateral Ligament
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ACL and PCL run from femur to tibia and form an X inside the knee
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The Collateral Ligaments
MCL: Medial Collateral Ligament Runs from medial femur to medial tibia LCL: Lateral Collateral Ligament Runs from lateral femur to head of fibula
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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
- 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 Stability Shock absorption
Lubrication and nutrition 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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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 – <body weight during walking 2.5 x body weight during stairs
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Patellar Tendonitis “Jumper’s Knee”
Inflammation and degeneration of the tendon that connects the kneecap (Patella) to the shin bone (Tibia).
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Chondromalacia Damage to the cartilage under the kneecap
Causes: abnormal patellar tracking Most Common Symptom: Knee pain when walking up and down stairs Prevention: strengthen quads Minimize squats, downhill running, biking with low seat
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Chondromalacia
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Patellar Dislocation Involves the patella sliding out of its position on the knee. Caused by direct blow or abnormal twisting of the knee Usually lateral
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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 “Baker’s Cyst”
Fluid accumulation in posterior knee (popliteal space) Patient usually complains of a mass behind the knee
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Prepatellar Bursitis “Housemaid’s Knee”
Tender swelling over the kneecap (prepatellar bursa)
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Pes Anserine Bursitis 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 SGT: Sartorius, Semitendinosis, Gracilis
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Knee Sprains
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ACL Sprain >200,000 injuries/year >100,000 reconstructions/year
Higher incidence in females 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. 50% of people describe a “pop” in knee 3. Knee fills with blood quickly Hemarthrosis 4. Usually immediate loss of motion 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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Mild hemarthrosis Posterior knee pain Walk with knee slightly flexed, avoid full extension Posterior sag of tibia 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
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
Apley’s Compression
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“The Unhappy Triad” Tear of the medial meniscus, anterior cruciate ligament (ACL), and medial collateral ligament (MCL)
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