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Knee Anatomy and Evaluation By Dr. Sue Shapiro Osseous Structures Formed by the articulations of femur, tibia, and patella. They form 2 articulations • Tibiofemoral joint • Patellofemural joint These two articulation are not independent of each other but have a biomechanical relationship Femur Anatomy Distal Aspect • Condyles • Articulate with patella and tibia. Posterior Aspect • Epicondyles Tibial Anatomy Tibial Plateus • Medial plateau • Lateral plateau Anterior Portion • Tibial tuberosity Tibiofemoral & Femoral Joints Motion in 2 planes • Flexion/Extension & IR/ER • Motion of the tibia on the femur • Femoral Rotation • Flex/Ext above meniscus • IR/ER below meniscus • The Screw Home Mechanism • Results in ER of the femur at terminal Ext. Patellofemoral Joint The patella a triangular in both sagital and frontal plane The superior portion ins wider than it distal part 5 distinct facets • super., infer., lateral, medial and odd Osseous Abnormalities Genus Varus and Valgus • Knock Knee - excessive valgus • Bowleg - excessive varus Genus Recurvatum - excessive extension Shallow Trochlear Groove - redisposed to ACL problems Patella Abnormalities - camel sign Osseous Abnormalities Extra Articular Structures Extensor Mechanism • Function • to provide deceleration of the patellofemoral articulation at different points along flexion/extension motion. • Lateral retinaculum- static stabilizer • Vastus Lateralis & IT band - dynamic stabilizers • Medial retinaculum- static stabilizer • Vastus Medialis & Adductor Magnus- dynamic stabilizers Extensor Mechanism Extensor Mechanism • Function • to provide deceleration of the patellofemoral articulation at different points • Lateral retinaculum- static stabilizer • Vastus Lateralis & IT band - dynamic stabilizers • Medial retinaculum- static stabilizer • Vastus Medialis & Adductor Magnus- dynamic stabilizers Extensor Mechanism Superior of the patella is supported by the lateral and medial patellofemoral ligament, and inferior by the patello-tibial ligament Q-Angle The relationship b/t line of pull of the quadriceps and the line of the tendon from the midpoint on the patella to its insertion on the tibial tuberosity. Normal ranges • Male - 13 degrees • Female - 18 degrees Patella Plica A fold in the synovial lining of the knee Signs • Aggravated by quadriceps exercise • + Moviegoer’s sign • Pop or snap as the knee is flexed and extended • Point tenderness at medial and lateral retinacular regions Joint Capsule Characteritics • Medial, lateral and anterior aspects arises superior to the femoral condyles and fixates distal to the tibial condyle • Posteriorly the capsule attaches to the posterior margins of the femoral condyles above the Jt. Line & inferiorly, to the posterior tibial condyle • Strength of the capsule is reinforced by the collateral lig. Medially & laterally, the retinaculum medially & laterally, the oblique popliteal lig. and the patella tendon • Capsular attachment of the menisci along the peipheral Collateral Ligament Medial Collateral Lig. • Deep & Superficial Layers • Primary Function is to protect the knee against valgus Lateral Collateral Lig. • No attachment to the capsule or meniscus • Primary restrain against varus forces Medial Knee Anatomy Medial Knee muscle Insertion • • • • • Semimembranosus Medial Gastroc VMO Adductor Magnus Pes Anerine Group Lateral Knee Anatomy Posteriorlateral Structures • Arcuate Lig. Complex • • • • Popliteous Muscle Lateral Grastroc Head Arcuate Lig. Posterior third of the capsular lig. Middle Third • LCL • Mid-lat capsular lig • Bicep Femoris Muscle Lateral Knee Anatomy Anteriorlateral Aspect • Joint Line • Lateral patellar restrainsts • Ilitibial Tract & insertion • Fibular head • Common peroneal nerve Posterior Compartment • Bicep Femoris • Semimmembranosis • Medial & lateral head gastroc • Popliteal fossa • Popliteal pulse Intra Articular Structures Menisci • Functions • Distributed WB load over a large surface area • To increase stability • Increase joint congruency by deepening the tibia plateau • Limits abnormal movements Menisci Peripheral Meniscus • The outer perimeter is vascular & has the ability to heal itself if torn. • Coronary ligament attach outer perimeter to tibial plateau Medial Meniscus • Avascular & can not heal if torn • Semimbranosus attaches to the posterior horn • C-shaped & attaches to the MCL and medial capsule Lateral Meniscus O-shaped Popliteus tendon attaches to the posterior horn & this causes pot. Translation during knee flexion Meniscus Biomechanics • Total Excursion (ant/post) • Medial - 6 mm • Lateral - 12 mm • Knee Extension • Kaplan’s Lig. Pulls menisci anteriorly • Knee Flexion • Semimembranosus pulls medial menisci • Popliteus pulls lateral menisci Mechanism of Injury • Flexion/ Rotation Injury • In flexed position (w/wt) trying to extend the post. Horns get trap and create a bucket handle tear which create pseudo-locking Types of Menisci Most commonly torn in the posterior horn Unusual for a anterior meniscal tear Second most common in middle Names of meniscus tear • Medial- Longitudinal, complex, horizontal. Cleavage • Lateral - Radial, longitudinal, bucket-handle Cruciate Ligaments Anterior Cruciate Lig. • Anatomy of ACL • Three Bundles – Anteromedial – Intermediate – Posterolateral • Special Teest – Anterior Drawer – Lachman’s Test • Functions of ACL – anterior displacement of tibia to the femur – Stabilizer of rotation Anterior Cruciate Lig Ligament Restrains • Anterior Stability • Provides 89% of restraint to anterior displacement • Secondary restraints 15% • Stress on ACL • Greatest stress (30-0 deg,) Factors affecting ACL rupture • • • • Equipment Design Technique Fitness Anatomy • • • • Intercodylar Notch Narrow Notch Quick Rotation (ER) Notchplasty • Braces • Prophylactic & Functional Anterior Cruciate Lig Signs and Symptoms • • • • • • Pivot: deceleration + valgus stress + ER tibia Hyperextension Direct contact 80-90% hear/feel “pop/click” Perception of the knee going out of place Accumulation of effusion over 2-24 hours Posterior Cruciate Lig. Anatomy • Two bundles • Blow to proximal tibia, or fall on flexed knee with plantar flexion • Posteromedial • Anteromedial Stability • Provides 95% of restraint to posterior displacement Function • Prevents posterior displacement of the tibia on femur Mechanism of Injury PCL Testing • • • • Recurvatum Sag Test Clancy’s Step Up Posterior Drawer Bursas Intracapsular • Suprapatellar • Subpopliteal • Semimembranosus Extracapsular • Prepatellar • Superficial infrapatellar • Deep infrapatellar Bursas Functions • During motion of flexion and extension synovial fluid moves throughout the bursal recesses to lubricate the articular surface and the bursas compress compressing fluid in many directions. • Give protection to articular surfaces at the sites of tendon attachment Reflexes and Cutaneous Distribution Reflexes • Patellar reflex ( L3 - L4) • Medial Hamstrings reflex (L5 - S1) Reflexes and Cutaneous Distribution Nerves • Tibial Nerve (L4-S3) • Common Peroneal Nerve (L4-S2) • Femoral Nerve (L2-L4) • Saphenous Nerve (L3-L4) Reflexes and Cutaneous Distribution Blood Supply • Popliteal Artery • Located in popliteal fossa