The Knee Flashcards
(38 cards)
What leg bone is not involved in the knee joint?
The fibular
What bony surfaces are involved in the knee joint?
- Condyles of femur
- Condyles of Tibia
- Patellar surfaces of Femur
- Articular surfaces of patella
What are the femoral condyles?
Medial is larger than lateral as it takes more weight
Between the condyles
- Anteriorly - shallow depression for patella articulation
- Posteriorly - Deep notch - intercondylar fossa (this contains the cruciate ligamnents which are attatched to the inner aspect of the condyles)
What is the tibial surface?
Tibial plateau
Medial surface is slightly concave
Lateral surface is slightly convex
There are separated by the intercondylar eminence (rough and attatch stuff)
What is the patella?
Largest sesamoid bone (develops within a tendon)
Provides mechanical advantage to quadriceps tendon.
What is the problem with the shape of the knee joint?
The Knee isn’t very stable
Mismatch of shapes.
“Like two balls on a table top”
How is the knee joint made more stable?
Deepen the articular surface of the tibial element - Menisci (crescent shapes bits of fibrous cartilage that are thicker on the edges than the middle.)
Support the joint by various structures:
- Ligaments
- Capsule
- Muscles
What are the menisci of the knee?
- Deepen the surface of articulation
- Crescent plates of fibrocartilage
- Shock absorbers
- Thicker at edges - wedge shapes
- Attached to intercondylar areas
- Are attatched to joint capsule via Coronary ligaments
- Anteriorly connected by transverse ligament of the knee
- Lateral meniscus is more mobile than the medial one
What ligaments are involved in the knee?
Cruciate ligaments (intra-capsular)
Oblique popliteal ligament (Ligaments that strengthen the capsule)
Collateral ligaments (extracapsular)
What are the cruciate ligaments?
Anterior - stops anterior displacement of the tibia on the femur. (The anterior passes posterior and inserts laterally)
Posterior - Stops posterior is placement of the tibia on the femur. (Posterior passes anterior inserts medially)
(If femur is reference point, swap it over)
What is the difference between the anterior cruciate ligament and the posterior cruciate ligament?
ACL is weaker of the two with a poor blood supply. It limits the anterior movement of Tibia on Femur.
Whereas, PCL is the stronger of the two. It limits the posterior movement of tibia on femur. In weight bearing, it flexes the knee. PCL is the main stabiliser.
What is the joint capsule?
Surrounds sides and posterior aspect of the joint.
- -It is deficient anteriorly
- Allows the synovial membrane to extend up beneath patella (supra-patellar bursa)
- Strengthened laterally
- Inferior fibres of Vastus lateralis / medialis
- Strengthened posteriorly
- Oblique popliteal ligament
- Expantion of semimembranosus
What are the extra-capsular ligaments?
Medial (Tibial) collateral ligament
- Medial Femoral epicondyle to Tibia
Lateral collateral ligament
- Lateral Femoral epicondyle to lateral surface of Fibular head
- Also reinforced by illiotibial tract
The medial tibial collateral ligament attaches to the medial meniscus at its medpint.
What are the movements of the knee?
Flexion - Hamstrings (Gastrocnemius)
Extension - Quadraceps (rectus femoris, vastus medialis, vastus intermedialis, vastus lateralis)
When knee is flexed you can get some rotation.
Medially - Semitendinosus
Laterally - Biceps Femoris
What muscles have a stabilising effect in the knee?
Most important is the quadriceps femoris.
Especially inferior fibres of
- Vastus medialis
- Vastus lateralis
Also the iliotibial tract laterally
What are the hamstrings?
These are at the back of the thigh. They are the semimembranosis, semitendinosis and the biceps femoris.
What is the femoral trangle?
The femoral triangle is an anatomical space in the upper inner thigh.
It is bound:
- superiorly by the inguinal ligament.
- medially by the lateral border of the adductor longus muscle.
- laterally by the medial border of the sartorius muscle.
It is important because many important structures pass through it:
- Femoral nerve and its (terminal) branches.
- Femoral sheath and its contents:
- Femoral artery and several of its branches.
- Femoral vein and its proximal tributaries (e.g., the great saphenous and deep femoral veins).
- Deep inguinal lymph nodes and associated lymphatic vessels.
What is locking of the knee?
- So it is less effort to stand
- Femur rotates internally over Tibia to lock
- In this position the knee joint can be help in position
- To ‘unlock’ -Popliteus helps to rotate the femur externally.
What are bursa?
Synovial sacs that cushion the interface between tendons and bones and other attachments.
There are three important ones:
- Supra-patellar bursa
- Pre-patellar bursa
- Superficial infra-patellar bursa
What people commonly get knee problems?
Young with sport injuries
Middle age with early onset arthritis
Old people with arthritis
And others..
Why are knee disorders important?
Major weight baring joint
Required for walking - Critial for health and fitness
Reduces mobility -predisposition to falls -Weight gain
Disability
Inability to work
Psychological issues -Depression -Social isolation
What are femoral shaft fractures?
- Usually High energy injuries
- Road Traffic Accident
- Falls from height
- Low velocity e.g fall if if:
- Osteoporitic
- Metastases
- Other bone lesions eg cyst
- Site
- Poximal
- Mid-shaft
- Suprcondylar
- Blood loss (if closed fracture)
- 1500ml (1.5L)
- Hypovolaemic shock (physiological response to trauma.)
- If fracture is open then blood loss may be double
- Traction splint
- Surgical fixation
What are tibial plateau fractures?
- High energy injury
- Axial loading and angulation
- Uni / Bi-condylar
- Lateral tibial condyle fractures most common
- Articular cartilage damage
- Instability
- Asociated with meniscal tears and ACL injury
- Accurate joint surface reduction
- Fix articular segment to shaft
- CT scan -Identify anatomy to piece back together
- Post traumatic osteoarthritis
What are Patella Fractures?
Direct or Indirect force
Is the extensor mechanism intact?
- (can you lift your leg off the floor / straight leg raise)
Displaced
- Reduce and Fix
Undisplaced
- Splint and protect
Lever arm for quadriceps
Pos traumatic OA
Blood supply via the inferior pole
Palpaple defect in patella and joint swollen due to blood (haemotharosis)
Beware of bipartite Patella (patella in two parts) which can be mistaken for a fracture.