Joints - Knee Flashcards
What type of joint is this?
Hinge type joint
Articulating surfaces?
There are two articulations. Surfaces are lined with hyaline cartilage.
1) Tibiofemoral - femoral condyles and tibial condyles. It is a weight-bearing component.
2) Patellofemoral - anterior aspect of distal femur and patella. Allows the tendon of the quadriceps femoris to be inserted directly over the knee, increasing the efficiency of the muscle.
Neurovascular supply?
Arterial supply
1) Genicular anastamoses around the knee. These are genicular branches of the popliteal and femoral arteries.
Innervation
1) Femoral nerve
2) Tibial nerve
3) Common fibular nerve
Menisci?
The medial and lateral menisci are fibrocartilage structures in the knee and serve two functions:
1) Deepen the articular surface of the tibia, increasing the stability of the joint.
2) Act as shock absorbers, increasing surface area to dissipate forces.
They are C-shaped and attached at both ends of the intercondylar area of the tibia.
The medial meniscus is also attached to the tibial collateral ligament and joint capsule. If the collateral ligament is damaged it will result in a meniscal tear.
Whereas the lateral meniscus doesn’t have any more attachments.
Bursae?
These aim to reduce wear and tear of the structures in the joint.
There are four bursae:
1) Suprapatellar - located between the quadriceps femoris and the femur.
2) Prepatellar - between apex of the patella and the skin.
3) Infrapatellar - split into deep and superficial. Deep lies between the tibia and patellar ligament. Superficial lies between patella ligament and skin.
4) Semimembranous - located posteriorly in the knee. Located between the semimembranosus and the medial head of gastronemius.
Ligaments?
1) Patellar ligament - continuation of the quadriceps femoris tendon distal to the patella - attaches to the tibial tuberosity.
2) Collateral ligaments - two strap-like ligaments - acts to stabilise the hinge motion of the knee, preventing excessive medial and lateral movement.
i) Tibial (medial) collateral ligament - medial epicondyle to the condyle of the tibia.
ii) Fibular (lateral) collateral ligament - lateral epicondyle to the lateral surface of fibular head.
3) Cruciate ligaments - these ligaments cross each other, connecting the femur and tibia.
i) Anterior cruciate ligament (ACL) - anterior intercondylar region of tibia where it then blends with the medial meniscus. Ascends posteriorly to insert on the intercondylar fossa of the femur. Prevents anterior dislocation of tibia onto the femur.
ii) Posterior cruciate ligament (PCL) - posterior intercondylar region of tibia and ascends anteriorly to the anteromedial femoral condyle. Prevents posterior dislocation of of tibia onto the femur.
Movements?
Extension - quadriceps femoris (that inserts into the tibial tuberosity).
Flexion - biceps femoris, gracilis, sartorius and popliteus.
Lateral rotation - biceps femoris
Medial rotation - semimembranous, semitendinosus, gracilis, sartorius and popliteus.
Clinical relevance - collateral ligament damage
Caused by force applied to the side of the knee when the foot is placed on the ground.
Damage can be assessed by asking the patient to medially rotate and laterally rotate the leg. If there is pain on medial rotation, there is damage to the medial collateral ligament, and vice versa.
If the medial collateral ligament is damaged it is likely that the medial meniscus is also damaged due to is attachment.
Clinical relevance - cruciate ligaments?
1) ACL - can be torn due to hyperextension of the knee joint or by applying a large force to the back of the knee when the joint is partially flexed.
To test for this, you can do an anterior draw test, where you attempt you pull the tibia forward, if it moves the ligament has been torn.
2) PCL - most common mechanism is of PCL is the ‘dashboard injury’. Occurs when the knee is flexed, and a large force is applied to the shins, pulling the tibia posteriorly. This is often seen in car accidents, where the knee hits the dashboard.
PCL can also be torn via hyperextension of the knee joint, or by damage to the upper part of the tibial tuberosity.
To test for PCL damage, perform the ‘posterior draw test’. This is where the clinician holds the knee in a flexed position and then pushes the tibia posteriorly. If there is movement, the ligament has been torn.
Clinical relevance - bursitis?
1) Housemaid’s knee (prepatellar bursitis) - friction between the skin and the patella.
2) Clergyman’s knee (infrapatellar bursitis) - friction between the skin and the tibia.
Clinical relevance - unhappy triad (blown knee)
Unhappy triad - damage to the medial collateral ligament, medial meniscus and ACL.
For example, this can happen during a rugby tackle of a leg while it is extended.
