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Biomechanics of the Knee

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  1. Biomechanics of the Knee Meagan Carnes, Kevin Chico, John Paul Dumas, Tanner Jones and Amy Loya

  2. Learning Objectives • Identify the bones of the knee and describe their characteristics which facilitate joint function • Name the ligaments in the knee joint and describe their function in the knee • Identify the major flexor and extensor muscles in the knee • Describe molecular structure of tendons and apply these properties to the various functions of a tendon • Differentiate between osteoarthritis and rheumatoid arthritis as they relate to the knee joint

  3. Bones of the knee • tibia • femur • fibula • patella

  4. knee joints • tibiofemoral joint – femur and tibia • patellofemoral joint – patella and femur

  5. Femur • specific structural characteristics of the posterior end of the femur allow it to successfully articulate with both the tibia and the patella • important characteristics: • medial & lateral condyles • patellar surface • intercondylar fossa

  6. Femoral Condyles • medial and lateral condyles • the condyles’ round nature allow them to articulate smoothly with the tibial plateau posterior view of right femur

  7. Intercondylar fossa • posterior, deep notch between the two condyles inferior view of right femur

  8. Patellar Surface • the central, anterior portion between condyles is grooved inferior view of right femur

  9. Patella • triangular shaped, sesamoid bone • anterior surface is convex, while the posterior surface is divided into a medial and lateral facets for articulation with the femur posterior surface of right patella

  10. Patella as a pulley • a pulley changes the direction of an applied force • the patella helps to support the work of the quadricep muscles during the contraction of the quadricep that allows for extension of the knee

  11. Tibia • the portion of the tibia proximal to the femur plays a significant role in the knee joint • important characteristics: • medial and lateral condyles/plateaus • intercondyloid eminence • tibial tuberosity anterior view posterior view

  12. Tibial Plateau • medial and lateral plateaus • oval and concave in shape

  13. Intercondyloid eminence • located between the plateaus, near the posterior end • tubercles on either side of the eminence • above and below are the intercondyloid fossa

  14. Tibiofemoral joint • due to the oblique nature of the femur, the angle at which the femur and tibia come in contact is not 180°, but rather 185° • deviation of more than 5° from this creates varied stresses on the medial and lateral components of the femur and tibia anatomical axis mechanical axis

  15. Cartilage of the Knee • Menisci • lateral meniscus and medial meniscus • Articular Cartilage • located on femur, tibia, and patella

  16. Articular Cartilage • hyaline cartilage on the articular surface of bone • located on the tibial and femoral condyles and the posterior portion of the patella • smooth, slippery surface that allows for minimal friction of the joint

  17. Menisci • lateral meniscus and medial meniscus are c-shaped fibrocartilage located on top of the tibial condyles • both together form a depression in which the femoral condyles sit

  18. Meniscus distributes stress

  19. Synovial Membrane • blood vessels begin to diminish in the meniscus over time, which limits the nutrition required to keep it healthy • the inner portion of the meniscus relies on the synovial fluid to gain nutrients • also useful in maintaining joint motion

  20. Femur ACL PCL Ligaments in the Knee LCL MCL LCL ACL – Anterior Cruciate Ligament PCL- Posterior Cruciate Ligament LCL – Lateral Collateral LigamentMCL-Medial Collateral Ligament Tibia Fibula

  21. ACL Tear In MRI test

  22. Actual ACL Tear

  23. Ligament Injuries • Three Classes of tendon injury(1, 2, 3) • Injuries to any of the ligaments are cause by • Twisting your knee with the foot planted. • Getting hit on the knee. • Extending the knee too far. • Jumping and landing on a flexed knee. • Stopping suddenly when running. • Suddenly shifting weight from one leg to the other.

  24. Symptoms of Injured Ligaments • Swelling • Severe Pain • Instability in Joint • Inability to load the joint • Hearing a pop sound when injured • Decreased Range of motion • Diminished Strength

  25. Testing Knee Ligaments • Lachman Test (ACL) • Piviot Shift Maneuvor (ACL) • Opposite of Lachman Test (PCL) • Valgus Stress Test (MCL) • Varus Stress Test (LCL) • MRI • Xrays • Testing Range of Motion • Testing Strength of Quad

  26. Treatment Options • Physical Therapy-rebuild knee strength, allow for ligament to heal on its own • Arthroscopic Surgery- Remove torn tissue, and stitch ligament back together • Orthopedic Surgery – Removal of torn ligament(s) and replaced by a new one. • Patella Tendon • Hamstring Tendon • Cadaver

  27. Orthopedic Surgery For The ACL • First the knee is probed to check knee joint • Torn ACL is removed by an electric shaver • Remove some femoral bone • Place graph in the correct position • Drill to create the Femoral Tunnel • Drill Tibial Tunnel into the joint • ACL graft is then passed through Tibial tunnel up through the femoral tunnel using a suture • http://www.youtube.com/watch?v=PjL7-tIsQhw • http://www.youtube.com/watch?v=q96M0jRqn7k

  28. Muscles of the Knee • Considered a mechanically weak joint • Multiple muscles cross the knee joint but we are primarily concerned with the main flexors/extensors. • Extensors – Quadriceps • Flexors – Hamstrings • Secondary functions are rotation and adduction/abduction leg • Two joint muscles

  29. Major Muscle Groups http://www.medicalook.com/human_anatomy/organs/Muscles_involved_in_knee_motion.html

  30. Extensors (Quadriceps) http://www.floota.com/quadricepsstretch.html

  31. Quadriceps (cont.) Rectus Femoris

  32. Force Modeling http://www.slideshare.net/SubhanjanDas/knee-biomechanics • For modeling these 4 muscles (RF, VL, VI, VM) can be represented by a single upward force • All 4 are controlled by the femoralnerve

  33. Additional Extensors • Muscles do not need to cross a joint to be involved in joint motion • The soleus (calf) and gluteus maximus can help extend when foot is on the ground

  34. Flexors (Hamstrings) • http://wavesport.ning.com/profiles/blogs/a-paddler-s-pelvis

  35. Hamstrings (cont.)

  36. Additional Flexors • Satorius • Longest muscle in the body • Responsible for rotating knee after flexion • Gracilis • Most superficial muscle on medial side of the knee • Popliteus • Responsible for locking the knee

  37. Sit-to-Stand Motion • Lombard’s Paradox • What is it? • How is it explained? • Muscles cannot develop different amounts of force in their different parts THE ACTION OF TWO-JOINT MUSCLES: THE LEGACY OF W. P. LOMBARD

  38. Quad and Hamstring Injuries • Rectus Femoris is most susceptible because it is in contact with the femur throughout its length • The muscle is more resistant to injury if it is struck while in a contracted non-fatigued state. • Hamstring injuries often caused by abrupt stops or starts A

  39. What are Tendons? • Tendons are bundles or bands of strong fibers that attach muscles to bones

  40. Knee Tendoncies Tendons associated with the knee joint include: Patellar Tendon Lateral Retinaculum Pes Anserine Tendons Biceps Tendon Popliteal Tendon Hamstring Tendon Quadriceps Tendon Semimembranosus Illiotibial Tendon Medial Retinaculum

  41. Anterior View Quadriceps Tendon Illiotibial Tendon Medial Retinaculum Lateral Retinaculum Patellar Tendon

  42. Posterior View Popliteal Tendon Biceps Tendon

  43. Medial View of Right Knee Quadriceps Tendon Semimembranosus Patellar Tendon Pes Anserine Tendons

  44. Lateral View of Right Knee Illiotibial Tendon Quadriceps Tendon Hamstring Tendon Lateral Retinaculum Patellar Tendon

  45. Tendon Injuries and Disorders • The three main types of tendon injuries and disorders are: • Tendinitis and ruptured tendons • Osgood-Schlatter disease • Iliotibial band syndrome • Treatment for tendon injuries and disorders include: • Rest • Ice • Elevation • Medicines such as aspirin or ibuprofen to relieve pain and reduce swelling • Limiting sports activity • Exercise for stretching and strengthening • A cast, if there is a partial tear • Surgery for complete tears or very severe injuries.

  46. Tendinitis and Jumper’s Knee

  47. Osgood-Schlatter Disease