Lecture 19: Knee joint

Question 1

what are the 2 articulations in the knee joint?

Answer 1

• between the femur and the tibia
• between the femur and the
  patella (Patellofemoral joint).
• The articular cavity of the knee
  joint includes both the
  patellofemoral joint and
  the tibiofemoral joint. (share the cavity and synovial fluid)

Question 2

what is the role of the meniscus?

Answer 2

The menisci increase stability for femorotibial articulation, distribute axial load, absorb shock, and provide lubrication and nutrition to the knee joint.

+increase SA for articulation between femur and tibia

Question 3

Answer 3

Question 4

what is the role of the patella( sesamoid bone )?

Answer 4

protects quad tendon

Question 5

what is a sesamoid bone?

Answer 5

A sesamoid bone is a small bone that is commonly found embedded within a muscle or tendon near joint surfaces, existing as focal areas of ossification and functioning as a pulley to alleviate stress on that particular muscle or tendon

Question 6

Answer 6

Question 7

Answer 7

Question 8

patella anatomy

Answer 8

• Patella has an upper and lower
  pole
• Patella is a sesamoid bone
  It sits in the tendon of the
  quadriceps muscles
• Attaches to tibial tuberosity of
  tibia
• Protects the quadreceps
  tendon

Question 9

normal alignment

Answer 9

*Weight of body is transmitted to centre of
hip joints
*Then down leg
*If leg is aligned well weight is transmitted
through the knee joint and ankle joint
= “Normal alignment” of lower limb
Minimises wear on joints and energy
required to stand or walk

Question 10

varus alignment

Answer 10

-normal in babies and older ppl (legs further apart to increase stability)
-knee joint is directed laterally
-apex of joint point out

Question 11

valgus alignment

Answer 11

-common in young girls-> grow out of it
-if not fixed-> puts pressure on the lateral aspects+ and tension on the medial ligaments-> stretched and weakened
-apex point in

Question 12

5 ligaments of the knee

Answer 12

-patellar lig/tendon
-the medial and lateral collateral ligs
-anterior and posterior cruciate lig

Question 13

patellar lig/tendon

Answer 13

• The Patellar ligament is the continuation of
  the quadriceps mechanism (making the patella a
  sesamoid bone).
• It is attached to the inferior margins of the
  patella (superiorly) and the tibial tuberosity
  (inferiorly).
• Clinically call it patella tendon as patella
  ligament is really continuation of quadriceps
  tendon

Question 14

The Medial and Lateral Collateral ligaments

Answer 14

• The Medial and Lateral Collateral
  ligaments (MCL and LCL) attach at the sides
  of the knee.
• The MCL runs from the medial femoral
  epicondyle to the medial tibia (posterior to the
  attachment of the Pes Anserinus).
• It is a broad ligament that blends with the
  underlying joint capsule.
• The LCL runs from the lateral femoral
  epicondyle to the fibula head.
• It is a cord-like ligament that is discrete from
  the joint capsule.
• Function – prevent knee going valgus or
  varus

Question 15

Answer 15

lateral collateral lig

Question 16

Answer 16

medial collateral lig

Question 17

Anterior and Posterior Cruciate ligaments

Answer 17

• Intracapsular
  -inside the capsule BUT not inside the synovial cavity
• The Anterior and Posterior Cruciate ligaments
  (ACL and PCL) run from the intercondylar
  region of the tibia ( ‘tibial spine’) to the distal
  femur
• Important in stabilizing the knee in the AP plane.
• The ACL runs from the anterior tibial spine to
  the lateral condyle of the femur. It prevents
  excessive anterior translation of the tibia on the
  femur (prevents the tibia sliding forward on
  femur)
• The PCL runs from the posterior tibial spine to
  the medial femoral condyle. It prevents
  posterior translation of the tibia on the femur.
  (prevents the tibia from sliding backwards on femur)

Question 18

knee joint capsule structure

Answer 18

The joint capsule isolates and covers the entire joint. It consists of two layers, an outer fibrous layer and an inner layer known as the synovial membrane.

• The joint capsule is the fibrous membrane that
  encloses the articular cavity.
• Attached is where the cartilage finishes
• Anteriorly the membrane is reinforced by the quads tendon and patella ligament.
• The synovial membrane is deep to the fibrous membrane and excludes the anterior and posterior cruciate ligaments

Question 19

bursae of the knee

Answer 19

The Prepatellar bursa is anterior to the patella.
* This can become inflamed with repeated
trauma e.g. kneeling for long periods of time.

• The Infrapatellar bursae are superficial and deep
  to the patellar ligament (inferior to the patella itself)
  and can also become inflamed and cause knee pain
• The prepatellar and infrapatellar bursae do
  not communicate with the knee joint
• The Suprapatellar bursa is in continuity with the knee joint and sits between the quads tendon and the distal femur.

Question 20

clinical relevance of suprapatellar bursa

Answer 20

• This is often where fluid will accumulate during a knee joint effusion.
• Good place to access the knee joint to aspirate fluid or inject into the knee

Question 21

menisci

Answer 21

There are two fibrocartilaginous menisci
within the knee joint- medial and lateral.

They improve the articulation between
the femur and the tibia as shape of the
surfaces changes throughout the full range
of motion.
Also act as “shock absorbers”

The medial meniscus is attached to the joint
capsule and MCL, making it less mobile.

The lateral meniscus is not attached to the
joint capsule and hence is more mobile.

Question 22

what is the problem with menisci?

Answer 22

fibrocartilage-> poor blood supply-> central meniscal tears won’t heal-> need to take out

Question 23

which meniscus is more commonly injured?

Answer 23

medial
attached to the joint capsule and MCL making it less mobile

Question 24

what is a good radiology scan to see tears in minisci?

Answer 24

MRI. White line= tear

Question 25

what is a good radiology scan to see tears in menisci?

Answer 25

MRI. White line= tear

Question 26

what is the most common knee dislocation?

Answer 26

hyperextension- anterior dislocation

Question 27

risks associated with knee dislocation

Answer 27

Neurovascular structures at risk: Popliteal artery and vein, Tibial and common fibular nerves + damage to the ligaments

Question 28

what is happening here? risks/ consequences/ concerns

Answer 28

comminuted Tibial fracture involving the joint -blood+ fat has come out of the bone into the joint capsule-> fat can get into the bloodstream -> fat emboli-> if in lungs- can die of hypoxia + trauma involving the joint predisposes to arthritis

Question 29

vascular supply to the knee

Answer 29

The vascular supply to the knee comes from: Branches of the femoral, lateral femoral circumflex and popliteal vessels (superiorly) anastomosing with branches of the: Anterior tibial and circumflex peroneal arteries (inferiorly). Main concept: Anastomoses Allow some blood to get to the leg if the the popliteal artery is blocked.

Question 30

nerve supply to the knee

Answer 30

* Knee joint is supplied by branches from the femoral, sciatic, and obturator nerves, which move the joint. * Some of these nerves go to the fibrous capsule and ligaments; others innervate this capsule and reach the synovial membrane.

Question 31

dermatome

Answer 31

A dermatome is an area of skin that is mainly supplied by cutaneous branches of a single spinal nerve

Question 32

myotome

Answer 32

A myotome is a group of muscles derived from one somite and supplied by a single spinal nerve (it is the motor equivalent of a dermatome) A myotome is defined as ‘a group of muscles innervated by a single spinal nerve root‘. They are clinically useful as they can determine if damage has occurred to the spinal cord, and at which level the damage has occurred. Most muscles in the upper and lower limbs receive innervation from more than one spinal nerve root. They are therefore comprised of multiple myotomes. Each muscle in the body is supplied by a particular level or segment of the spinal cord and by its corresponding spinal nerve. The muscle and its nerve make up a myotome.

Question 33

patterns/rules of myotomal supply:

Answer 33

* Muscles with common action have a common segmental supply i.e. all muscles which act to flex the hip have the same myotome(or two); they are innervated by L2 and L3. * Opposing muscles supplied by subsequent segmental levels i.e. muscles acting to extend the knee are supplied by L3 and L4; Those acting to flex the knee are supplied by L5 and S1. * Each joint distally supplied by 1 segment lower in the cord i.e. knee movements produced by muscles supplied by L3-S1; ankle movements produced by muscles supplied by L4-S2.

Question 34

match spinal lvl to action

Answer 34

Question 35

clinical importance of Pes Anserinus( goose foot)

Answer 35

The Pes Anserinus (meaning “goose’s foot”) is the insertion of the tendons of Sartorius, Gracilis and Semitendinosus onto the medial surface of the proximal tibia. These tendons can be used to reconstruct a torn ACL.

Question 36

terrible/unhappy triad

Answer 36

This a common injury pattern resulting from a lateral (valgus) force to the knee. The three structures involved are typically the medial collateral ligament, anterior cruciate ligament and medial (or lateral) meniscus.