M: The knee joint Flashcards
What 2 conditions are the common causes of chronic knee pain/swelling?
1) Osteoarthritis
2) Burisitis
What 3 atraumatic conditions can result in acute knee swelling/pain?
1) Acute gout
2) Flare of OA or RA
3) Septic joint
What kind of joint is the knee joint?
Synovial hinge joint
Which 3 bones are involved in the knee joint?
1) Distal femur
2) Proximal tibia
3) Patella
What 3 articulations make up the knee joint?
1) Medial femorotibial
2) Lateral femorotibial
3) Femoropatellar
The medial and lateral femorotibial articulations are between which joint surfaces?
Medial and lateral tibial plateaus (flattened top surfaces of tibial condyles) and the medial and lateral femoral condyles
What are the 4 possible movements of the knee joint?
1) Extension
2) Flexion
3) Medial rotation of leg when knee joint flexed at 90 degrees
4) Lateral rotation of leg when knee joint flexed at 90 degrees
Why is some knee flexion lost when the hip is extended?
Due to loss of tension on hamstrings
When can rotation of the knee occur?
Only when the knee is flexed and the collateral ligaments are relaxed
What is locking of the knee, when does it occur?
Occurs as the joint approaches full extension, femur undergoes a few degrees of medial rotation on the tibia
Why is locking of the knee important?
It provides a very stable position when the leg is in full extension so that the thigh muscles can relax
Which muscle is involved in unlocking the knee, why is this necessary?
Popliteus muscle - laterally rotates the femur
Knee need to be unlocked in order to flex the knee from extension
Why is the knee joint said to be incongruent, what structures improves the congruency of the knee joint?
Tibial plateau is a poor fit for the rounded femoral condyles
Tibial plateau is deepened - thus congruency is improved - by 2 plates of fibrocartilage called the menisci
Is the knee joint more or less stable in extension or flexion, why?
Most stable in extension
because the joint is most congruent in this position
What are the menisci?
2 c-shaped wedges of fibrocartilage which are thicker at the external margins
What are the 4 functions of the menisci?
1) Increase joint congruency
2) Distribute weight evenly across the knee joint
3) Shock absorption
4) Assist in locking mechanism
What do the menisci attach to?
The external edges of both menisci attach to the fibrous capsule of the joint
The medial meniscus is also firmly attached to the tibial collateral ligament
What is the clinical significance of the relationship between the medial meniscus and the tibial collateral ligament?
Rupture to the tibial collateral ligament will also result in injury to the medial meniscus
Unlike the lateral meniscus which is not attached to the fibular collateral ligament and you can therefore get isolated injuries
What is the likely cause of a meniscal tear?
Sports injury or degenerative changes
Why does the knee become painful or lock in a meniscal tear?
Get displaced cartilage which can become trapped during knee movement
What is the treatment for a meniscal tear?
Repair or resection
Damage to the menisci is associated with development of what condition?
Osteoarthritis
Which 3 things increase the stability of the joint, which has the most effect?
1) Ligaments inside the joint - intra-articular
2) Ligaments outside the joint - extra-articular
3) Surrounding muscles - have the biggest influence on stability