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Knee Conditions

Knee Conditions. Chapter 18. Anatomy. Anatomy (cont.). Anatomy (cont.). Tibiofemoral Joint. Condyles of femur with plateaus of tibia Hinge joint—flexion/extension Tibia does rotate laterally on femur during last few degrees of extension “Screw-home mechanism”

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Knee Conditions

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  1. Knee Conditions Chapter 18

  2. Anatomy

  3. Anatomy (cont.)

  4. Anatomy (cont.)

  5. Tibiofemoral Joint • Condyles of femur with plateaus of tibia • Hinge joint—flexion/extension • Tibia does rotate laterally on femur during last few degrees of extension • “Screw-home mechanism” • Produces a locking of the knee in final degrees during extension • Close-packed position of full extension

  6. Meniscus • Fibrocartilaginous discs attached to tibial plateaus • Medial and lateral • Functions: • Stabilize joint by deepening the articulation • Shock absorption • Provide lubrication and nourishment • Improve weight distribution

  7. Joint Capsule and Bursae • Articular capsule – encompasses both tibiofemoral and patellofemoral joints • Suprapatellar bursa • Subpopliteal bursa • Semimembranosus bursa • Bursa outside capsule • Prepatellar bursa • Superficial infrapatellar bursa • Deep infrapatellar bursa

  8. Ligaments • ACL • Prevents: • Anterior translation of tibia on femur • Rotation of tibia on femur • Hyperextension • Discrete bands • Knee full extension—posterolateral bundle is taut • Knee full flexion—anteromedial bundle is taut

  9. Ligaments (cont.) • PCL • Resists posterior displacement of tibia on femur • Knee full extension—posterior fibers are taut; knee full flexion—anterior fibers are taut

  10. Ligaments (cont.) • MCL • Resist medially directed (valgus) forces • Complete extension—tautmidrange—posterior fibers most tautcomplete flexion—anterior fibers most taut • LCL • Resist laterally directed (varus) forces

  11. Ligaments (cont.) • Arcuate-popliteal complex • Oblique popliteal ligament and arcuate popliteal ligament • Supports posterior joint capsule • Limits anterior displacement of tibia on femur • Limits hyperextension and hyperflexion

  12. Iliotibial Band • Extends from tensor fascia latae to Gerdy’s tubercle on lateral tibial plateau • Lateral knee stabilizer

  13. Patellofemoral Joint • Patella • Superior, middle, and inferior articular surfaces • Functions • Protect femur • Increase effective power of quadriceps

  14. Q-Angle • Q-angle • Angle between line of resultant force produced by quadriceps and line of patellar tendon • Males 13°; females 18° •  Q-angle— lateral patellofemoral contact  Q-angle— medial tibiofemoral contact • A-angle • Measures relationship of patella to tibial tubercle • 35° or greater linked to increased patellofemoral pain

  15. Muscles • Produce movement • Stabilize the knee

  16. Nerves • Tibial nerve • Hamstrings except short head of biceps • Common peroneal • Short head of biceps • Femoral • Quadriceps

  17. Blood Supply • Femoral artery • Popliteal artery • Genicular arteries

  18. Kinematics • Knee flexion • Hamstrings • Assisted by: • Popliteus • Gastrocnemius • Gracilis • Sartorius

  19. Kinematics (cont.) • Knee extension • Quadriceps femoris muscle group • Rectus femoris • Vastus lateralis • Vastus intermedius • Vastus medialis • Vastus medialis oblique (VMO) • Screwing-home motion • Rotation and passive abduction and adduction • Capability maximal at approximately 90° of knee flexion

  20. Kinematics (cont.) • Knee motion during gait • Midstance – flexed 20°, internally rotated 5°, and slightly abducted • Swing phase – flexed 70°, externally rotated 15°, and 5° adduction • Patellofemoral joint motion • With knee flexion and extension, patella glides in the trochlear groove • Tracking is dependent on the direction of the net force produced by the attached quadriceps

  21. Kinetics • Forces at the tibiofemoral joint • Compression and shear during daily activities • Extension—weight bearing and tension in muscles ↑ compression • Flexion—as angle of joint ↑ to 90 → ↑ shear force produced by weight bearingshearing—tendency for the femur to displace anteriorly • Forces at patellofemoral joint • Compression during normal walking (50% body weight); increases with stair climbing

  22. Prevention of Knee Injuries • Physical conditioning • Strength • Flexibility • Rule changes • Footwear • Cleats vs. flat sole • Position of cleats and size

  23. Contusions • Knee • Mechanism: compression • S&S • Localized tenderness • Pain • Swelling • Management: standard acute • Caution: excessive swelling could mask other injuries

  24. Contusions (cont.) • Infrapatellar fat pad • Entrapped between the femur and tibia • S&S • Locking, catching, giving way • Palpable pain on either side of patellar tendon • Extreme pain on forced extension • Management: standard acute

  25. Contusions (cont.) • Peroneal nerve • Mechanism: blow to the posterolateral aspect of the knee

  26. Contusions (cont.) • S&S • Radiating pain down lateral aspect of leg and foot • Severe cases • Initial pain—not immediately followed by tingling or numbness • As swelling ↑ within nerve sheath • Weakness in dorsiflexion or eversion • Loss of sensation in dorsum of foot, especially between 1st and 2nd toes • May progressively occur days or weeks later • Management: standard acute; severe S&S—immediate physician referral

  27. Bursitis • Prepatellar • Mechanism • Acute: direct blow to anterior patella • Chronic: repetitive blows • S&S • Swelling • Pain with direct pressure • Pain with passive knee flexion • Localized swelling

  28. Bursitis (cont.) • Pes anserine • Mechanism: • Friction between tendon and MCL • Direct trauma • S&S • Pain with knee flexion

  29. Bursitis (cont.) • Infrapatellar • Mechanism: • Friction between patellar tendon and fat pad/tibia • May be associated with patellar tendinitis • S&S • Point tender with possible swelling posterior to patellar tendon •  pain at end range of resisted knee extension and passive flexion • Prolonged knee flexion may symptoms

  30. Bursitis (cont.) • Baker’s cyst • Posterior aspect of knee—most often: semimembranosus •  pain with full extension or flexion • Bursitis management • Standard acute;  aggravating activities

  31. Ligamentous Conditions • AAOS classifies ligamentous knee injuries according to: • Functional disruption of a specific ligament • Amount of laxity • Direction of laxity • Direction divides laxity into 4 straight and 4 rotatory laxities • Knowing knee position at impact and direction the tibia displaces or rotates indicates the damaged structures

  32. Ligamentous Conditions (cont.)

  33. Ligamentous Conditions (cont.)

  34. Ligamentous Conditions (cont.) • Straight medial laxity (valgus laxity) • Involves MCL; posterior medial capsule—possibly PCL • Lateral forces cause tension on medial aspect of knee • 1st degree • Mild pain medial joint line • Little or no joint effusion/mild swelling at site • Full ROM with minor discomfort • Valgus @ 0°—stable; @ 30º—+

  35. Ligamentous Conditions (cont.) • 2nd degree • Valgus @ 30º—+ (with positive end feel) • Unable to fully extend the leg; often walk on the ball of foot • 3rd degree • Valgus @ 0—+ (with a soft or absent end feel)

  36. Ligamentous Conditions (Cont’d) • Straight lateral laxity (varus laxity) • Involves LCL, lateral capsular ligaments, PCL • Medial forces produce tension on lateral aspect of knee • Not usually isolated—presence of IT band, biceps femoris, popliteus

  37. Ligamentous Conditions (cont.) • S&S • Similar to MCL • Swelling minimal—no attachment to capsule • + varus @ 30º • Instability may not be obvious if other stabilizers are intact

  38. Ligamentous Conditions (cont.) • Straight anterior laxity (anterior instability) • Anterior displacement of tibia on femur • Involves ACL—rarely isolated • Mechanism: cutting or turning maneuver, landing, or sudden deceleration

  39. Ligamentous Conditions (cont.) • S&S • Pain • Minimal and transient to severe and lasting • Deep in knee difficult to pinpoint • “Pop” • Effusion within 3 hours; reports knee giving way—does not feel right

  40. Ligamentous Conditions (cont.) • Straight posterior laxity • Tibia displaced posteriorly • Involves PCL • Mechanism • Hyperextension force • Fall on flexed knee (initial contact at tibial tuberosity)

  41. Ligamentous Conditions (cont.) • S&S • Sense of stretching to posterior knee • “Pop” • Rapid joint effusion • ↓ knee flexion due to effusion • + reverse Lachman’s test; posterior sag

  42. Ligamentous Conditions (cont.) • Anteromedial instability • Anterior external rotation of medial tibia condyle on femur • Involves MCL and oblique popliteal ligament, potentially ACL and medial meniscus • S&S • + valgus @ 0 & @ 30° • + Slocum drawer test; + Lachman’s test • ↑ anterior translation of the medial tibial plateau (w/ special tests)

  43. Ligamentous Conditions (cont.) • Anterolateral instability • Anterior internal subluxation of lateral tibial condyle on femur • Caused by a sudden deceleration and cutting maneuver • Involves ACL, IT band, lateral capsule • S&S • ↑ anterior translation of the lateral tibial plateau (with special tests)

  44. Ligamentous Conditions (cont.) • Posteromedial instability • Medial tibial plateau shifts posteriorly on the femur and opens medially • Involves superficial MCL, ACL, PCL, posteromedial capsule, and oblique popliteal ligament • S&S: + posteromedial drawer test and posteromedial pivot shift test

  45. Ligamentous Conditions (cont.) • Posterolateral instability • Lateral tibial plateau rotates posteriorly • Due to hyperextension with varus • Involves PCL, arcuate–popliteal complex, posterolateral capsule, and LCL • S&S • Soft end point with varus stress at 0° and 30° • + posterolateral drawer and external rotation recurvatum tests

  46. Instabilities of the Knee

  47. Ligamentous Conditions (cont.) • Management • Standard acute; NSAIDs • Physician referral—timing dependent on severity

  48. Knee Dislocation/Subluxation • Minimum of 3 ligaments must be torn for knee to dislocate • Most often—ACL, PCL, and one collateral ligament • Concern: damage to other structures; especially neurovascular • S&S • Individual describes severe injury • “Pop” • Deformity (unless spontaneously reduced) • Management: standard acute • Spontaneous reduction—physician referral • Not reduced—activate EMS

  49. Meniscal Conditions • Classified according to location • Involve compression, tension, shearing forces • Longitudinal • Twisting motion when foot fixed and knee flexed • Produces compression and torsion on posterior peripheral attachment • Bucket-handle tear • Longitudinal segment displaced medially toward center of tibia

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