Transcript Bones of the knee

Biomechanics of the Knee
Meagan Carnes, Kevin Chico, John Paul
Dumas, Tanner Jones and Amy Loya
Learning Objectives
1. Identify the bones of the knee and describe their
characteristics which facilitate joint function
2. Name the ligaments in the knee joint and describe
their function in the knee
3. Identify the major flexor and extensor muscles in
the knee
4. Describe molecular structure of tendons and apply
these properties to the various functions of a
tendon
5. Differentiate between osteoarthritis and
rheumatoid arthritis as they relate to the knee joint
Bones of the knee
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2.
3.
4.
tibia
femur
fibula
patella
knee joints
•tibiofemoral joint – femur and tibia
•patellofemoral joint – patella and femur
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
Femoral Condyles
• medial and lateral condyles
• the condyles’ round nature allow them to
articulate smoothly with the tibial plateau
posterior view of right femur
Intercondylar fossa
• posterior, deep notch between the two condyles
inferior view of right femur
Patellar Surface
• the central, anterior portion between
condyles is grooved
inferior view of right femur
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
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
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
Tibial Plateau
• medial and lateral plateaus
• oval and concave in shape
Intercondyloid eminence
• located between the plateaus, near the posterior end
• tubercles on either side of
the eminence
• above and below are the
intercondyloid fossa
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
mechanical
axis
anatomical
axis
Cartilage of the Knee
• Menisci
– lateral meniscus and medial meniscus
• Articular Cartilage
– located on femur, tibia,
and patella
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
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
Meniscus distributes stress
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
Ligaments in the Knee
ACL
ACL – Anterior Cruciate
Ligament
PCL- Posterior Cruciate
Ligament
LCL – Lateral Collateral
Ligament
MCL-Medial Collateral
Ligament
LCL
Femur
PCL
MCL
LCL
Tibia
Fibula
ACL Tear In MRI test
Actual ACL Tear
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.
Symptoms of Injured Ligaments
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Swelling
Severe Pain
Instability in Joint
Inability to load the joint
Hearing a pop sound when injured
Decreased Range of motion
Diminished Strength
Testing Knee Ligaments
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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
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
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=q96M0jRqn7
k
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
Major Muscle Groups
http://www.medicalook.com/human_anatomy/organs/Muscles_involved_in_knee_motion.html
Extensors (Quadriceps)
http://www.floota.com/quadricepsstretch.html
Quadriceps (cont.)
Rectus
Femoris
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
http://www.slideshare.net/SubhanjanDas/knee-biomechanics
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
Flexors (Hamstrings)
•
http://wavesport.ning.com/profiles/blogs/a-paddler-spelvis
Hamstrings (cont.)
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
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
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
What are Tendons?
Tendons are bundles or bands of strong fibers that
attach muscles to bones
Knee Tendoncies
Tendons associated with the knee joint include:
Anterior View
Posterior View
Medial View of Right Knee
Lateral View of Right Knee
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.
Tendinitis and Jumper’s Knee
Osgood-Schlatter Disease
Inflammatory Conditions of the Knee Joint
1. Bursitis
2. Tendonitis
3. Synovitis
http://www.aidmybursa.com/bursitis/bursitis-information.php
http://www.eorthopod.com/sites/default/files/images/knee_prepatellar_intro01.jpg
Treating Inflammatory Conditions
R.I.C.E.
Steroid Injections
Analgesics
Surgery in Severe Cases
http://www.kelseypro.com/Vaso/Synovectomy_knee_dyn.jpg
http://www.eorthopod.com/sites/default/files/images/knee_prepatellar_intro01.jp
Forms of Arthritis Affecting the Knee Joint
1. Osteoarthritis
2. Rheumatoid Arthritis
3. Post-traumatic Arthritis
http://www.barc.org.uk/arthritis/rheumatoid/index.html
Osteoarthritis in the Knee Joint
http://orthoinfo.aaos.org/topic.cfm?topic=a00389
Rheumatoid Arthritis
http://www.lurj.org/article.php/vol2n1/arthritis.xml
Osteoarthritis
http://orthoinfo.aaos.org/topic.cfm?topic=a00389
Treating Arthritic Conditions
• Osteoarthritis
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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
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
http://orthoinfo.aaos.org/topic.cfmtopic=a00389
http://www.healthline.com/health/total-knee-replacement-surgery/statistics-infographic
Components of the Knee Replacement
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2.
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4.
Metal Femoral Component
Metal Tibial Component
Plastic Patellar Component
Plastic Articulating Spacer
http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/health_tools/knee_replacement_slideshow/agefoto_rf_photo_of_knee_replacemen
t_compnents.jpg
http://www.hss.edu/conditions_arthritis-of-the-knee-total-knee-replacement.asp
Components of the Knee Replacement
http://orthoinfo.aaos.org/topic.cfmtopic=a00389
Different Types of Materials Used
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Stainless Steel
Cobalt-chromium Alloys
Titanium and Titanium Alloys
Uncemented implants
Tantalum
Polyethylene
Zirconium
http://bonesmart.org/knee/knee-replacement-implant-materials/
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
http://www.healthline.com/health/total-knee-replacement-surgery/statistics-infographic
http://arthritiskerala.com/disease-treatment.php?id=7
http://sentarainfo.com/today/2012/02/the-sounds-of-caring/
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.
1. Determine Fquad required
to hold the lower leg in
static equilibrium
2. Determine the joint
reaction force of the femur
Fquad
T
30°
Rx
48 N
Ry