The Knee Some slides adapted from University of Wisconsin Medical School.

The Knee One of the most complex joints Provides stability in weight bearing and locomotion Very vulnerable – especially medially and laterally Muscles and ligaments provide most of the stability

Instability - Example Patellar dislocation http://www.carletonsportsmed.com/Libraria_medicus/PF_patella_dislocation.JPG

Bony Anatomy – 4 bones Femur Patella Tibia Fibula

Bony Anatomy Femur: Longest Bone in Body Tibia: WB bone of lower extremity Fibula: Site of Muscle Attachment Patella: Sesamoid Bone Floating bone A bone that develops within a tendon

Knee Skeletal Lateral Condyle Head of Fibula Femoral Groove Gerdy’s Tubercle Tibial Tuberosity Pes Anserine

Sagittal MRI View

Knee Menisci 2 oval shaped (semilunar) fibrocartilages Provides cushion Avascular (poor blood supply) = decreased healing Medial – “C” shaped Lateral – “O” shaped

Menisci Medial Meniscus Lateral Meniscus PCL ACL

4 Stabilizing Ligaments Posterior Cruciate 2 cruciate ligaments ACL/PCL 2 collateral ligaments MCL/LCL Anterior Cruciate * The stabilizing roles of each ligament include: The medial collateral ligament (MCL) prevents the knee from buckling inwards (valgus injury) The lateral collateral ligament (LCL) prevents the knee from buckling outwards (varus injury) The anterior cruciate ligament (ACL) prevents the tibia from sliding forward under the femur The posterior cruciate ligament (PCL) prevents the tibial from sliding backward under the femur Medial Collateral Lateral Collateral

Anterior Cruciate Ligament (ACL) Extends from tibia posteriorly and laterally to femur Front of tibia to back of femur Prevents anterior movement of tibia Stabilizes against tibial rotation Main stabilizer

ACL Torn during cutting motions Foot planted and knee rotates More commonly torn in girls Less muscle, hormones, Q- angle Surgery Cadaver graph, patellar tendon, hamstring tendon About 6-9 months to return to activity

Healthy ACL

Torn ACL

Knee Posterior

Posterior Cruciate Ligament (PCL) Extends antiorly and medially from tibia to posterior femur Prevents tibia from posterior translation Prevents hyperextension

Medial Collateral Ligament MCL Medial side Thick Band of Tissue Tibia  Femur Resists Valgus Force

Valgus Outside to Inside Force MCL resists this force Occurs in FRONTAL PLANE

Increased Valgus

Lateral Collateral Ligament LCL Lateral side Narrow cord-like band of tissue Connects femur to head of fibula Resists Varus Force

Varus Inside to Outside Force LCL resists this force FRONTAL PLANE

Collateral Ligament Ruptures 3 degrees of sprains (ligament damage) Complete tear = 3rd degree sprain

Ligament Structures

What do you see? Look at the left knee.

Lateral View of Left Knee

Ruptured Patellar Tendon 3rd degree Strain = muscle/tendon injury

Lab Activity Partner up Get a marker Identify structures of the knee Patella Head of fibula Tibial tuberosity Pes Anserine Gerdy’s Tuburcle MCL LCL Medial Joint Line Lateral Joint Line Patellar Tendon

Normal Knee – Anterior, Extended

Surface Anatomy - Anterior, Extended* Patella Indented Hollow Appears hollow on either side of patella There is a slight indentation above the patella A small amount of fluid will make these hollow-appearing areas disappear. Larger effusions are most conspicuous as a fullness proximal to the patella.

Normal Knee – Anterior, Flexed

Surface Anatomy - Anterior, Flexed Patella Tibial Tuberosity Head Of Fibula

Lateral and Medial Patellar Facets Palpation – Anterior* Patella: Lateral and Medial Patellar Facets Superior And Inferior Patellar Facets *Assess for tenderness, edema, warmth **Palpate the insertion of the patellar tendon on tibial tubercle in adolescents (location of pain in Osgood-Schlatter syndrome in adolescents) Medial Fat Pat Lateral Fat Pad Patellar Tendon**

Surface Anatomy - Medial Patella Tibial Tuberosity Medial Femoral Condyle Joint Line Medial Tibial Condyle

Palpation - Medial Medial Collateral Ligament (MCL)* Pes anserine bursa** Medial joint line *Assess for tenderness along entire course of ligament from origin on medial femoral condyle to insertion on proximal tibia. **Pes anserine bursa is about 3 finger widths inferior to the medial joint line and contains the insertion site for the sartorius, gracilis, and semitendinosis muscles

Surface Anatomy – Lateral Patella Quadriceps Tibial Tuberosity Head Of Fibula

Palpation – Lateral* Lateral Collateral Ligament (LCL)** Lateral joint line * The LCL and joint line are more easily palpated with the knee in 90 degrees of flexion. ** LCL originates on lateral femoral epicondyle and inserts on fibular head

You should have the following drawn on your partner’s knee Patella Head of fibula Tibial tuberosity Medial joint line Lateral joint line Patellar tendon MCL LCL Pes Anserine Gerdy’s tubercule

Quadriceps and Patellar Tendons Quadriceps Tendon All 4 muscles come together at patella Patellar Tendon From inferior patella to tibial tuberosity

Quadriceps Anterior Thigh Musculature Four Muscles: Extend the Knee Rectus Femoris Vastus Lateralis Vastus Medialis Vastus Intermedius Extend the Knee

Quadriceps

Rectus Femoris 2 Joint Muscle Flexes Hip Extend the knee Crosses hip and knee Flexes Hip Extend the knee Converges with rest of quadriceps muscles at tibial tubercle

Hamstrings Three Muscles Common Origin the ischial tuberosity Semimembranosus Semitendinosus Biceps Femoris Common Origin the ischial tuberosity Flex the Knee

Hamstrings

Popliteus

Popliteus