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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 posterior view of right femur
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 Articular Cartilage
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 Ligaments in the Knee ACL – Anterior Cruciate Ligament
Femur ACL ACL – Anterior Cruciate Ligament PCL- Posterior Cruciate Ligament LCL – Lateral Collateral Ligament MCL-Medial Collateral Ligament PCL LCL MCL LCL 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


28 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

29 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

30 Major Muscle Groups

31 Extensors (Quadriceps)

32 Quadriceps (cont.) Rectus Femoris

33 Force Modeling For modeling these 4 muscles (RF, VL, VI, VM) can be represented by a single upward force All 4 are controlled by the femoral nerve

34 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

35 Flexors (Hamstrings)

36 Hamstrings (cont.)

37 Additional Flexors Gracilis Popliteus 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

38 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

39 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

40 What are Tendons? Tendons are bundles or bands of strong fibers that attach muscles to bones


42 Tendons associated with the knee joint include:
Knee Tendoncies Tendons associated with the knee joint include: Lateral Retinaculum Patellar Tendon Pes Anserine Tendons Biceps Tendon Popliteal Tendon Popliteal tendon Biceps tendon at the head of the fibula Pes anserine tendons Patellar tendon Quadriceps tendon Hamstring tendon Illiotibial tendon Medial retinaculum Lateral retinaculum semimembranosus Hamstring Tendon Quadriceps Tendon Semimembranosus Illiotibial Tendon Medial Retinaculum

43 Anterior View Quadriceps Tendon Illiotibial Tendon Medial Retinaculum
Lateral Retinaculum Patellar Tendon

44 Posterior View Popliteal Tendon Biceps Tendon

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

46 Lateral View of Right Knee
Illiotibial Tendon Quadriceps Tendon Hamstring Tendon Lateral Retinaculum Patellar Tendon

47 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.

48 Tendinitis and Jumper’s Knee

49 Osgood-Schlatter Disease


51 Inflammatory Conditions of the Knee Joint
1. Bursitis 2. Tendonitis 3. Synovitis

52 Treating Inflammatory Conditions
R.I.C.E. Steroid Injections Analgesics Surgery in Severe Cases

53 Forms of Arthritis Affecting the Knee Joint
Osteoarthritis Rheumatoid Arthritis Post-traumatic Arthritis

54 Osteoarthritis in the Knee Joint

55 Rheumatoid Arthritis Osteoarthritis

56 Treating Arthritic Conditions
Osteoarthritis Rest Analgesics Steroid Injections Decreased Use Knee Replacement surgery as a last resort Rheumatoid Arthritis Analgesics Physical Exercise Surgery to remove damaged synovial fluid when caught early Knee Replacement surgery as a last resort

57 Knee Replacement- Knee Arthroscopy
“96% of Knee Replacements are due to osteoarthritis” “Osteoarthritis was the 4th most frequent principal diagnosis for hospital stays in 2009.” “Approximately 12% of adults over 60 have symptoms of knee osteoarthritis.” Natalie Fawzi, July 2012

58 Components of the Knee Replacement
Metal Femoral Component Metal Tibial Component Plastic Patellar Component Plastic Articulating Spacer

59 Components of the Knee Replacement

60 Different Types of Materials Used
Stainless Steel Cobalt-chromium Alloys Titanium and Titanium Alloys Uncemented implants Tantalum Polyethylene Zirconium

61 Pros and Cons Minimally invasive
80% of current knee replacements last for up to 20 years Greatly improve knee functioning and restore a good quality of life 90% of patients experience a radical decrease in pain 6.1% of patients experience a complication during the hospital stay 7.5% experience a complication within 90 days of the procedure Revision rates 0.2% within 90 days 3.7% within 18 months 6% after 5 years 12% after 10 years

62 Problem! Givens: Quadriceps tendon is inserted on the tibia 5 cm from the knee joint, and is at a 30deg angle. Weight of the lower leg Is 48 N. Center of gravity of the lower leg is 0.20 m from the knee joint. Determine Fquad required to hold the lower leg in static equilibrium Determine the joint reaction force of the femur

63 Fquad T 30° Rx Ry 48 N

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