osteoarthritis

Question 1

knee joint - articulations

Answer 1

• The knee joint consists of two articulations – tibiofemoral and patellofemoral. The joint surfaces are lined with hyaline cartilage and are enclosed within a single joint cavity.
  • Tibiofemoral – medial and lateral condyles of the femur articulate with the tibial condyles. It is the weight-bearing component of the knee joint
  • Patellofemoral – anterior aspect of the distal femur articulates with the patella. It allows the tendon of the quadriceps femoris (knee extensor) to be inserted directly over the knee – increasing the efficiency of the muscle

Question 2

knee joint - ligaments

Answer 2

• The ligaments of the knee joint:
  1. Patellar ligament – a continuation of the quadriceps femoris tendon which attaches the patella to the tibial tuberosity.

2 + 3. Collateral ligaments – two strap-like ligaments. They act to stabilise the hinge motion of the knee, preventing excessive medial or lateral movement
 Tibial collateral ligament – wide and flat ligament, found on the medial side of the joint.
 Fibular collateral ligament – thinner and rounder than the tibial collateral

4. Cruciate Ligaments – these two ligaments connect the femur and the tibia. In doing so, they cross each other, hence the term ‘cruciate’ (Latin for like a cross)
    Anterior cruciate ligament
    Posterior cruciate ligament

• The medial and lateral menisci are fibrocartilage structures in the knee that serve two functions:
  • To deepen the articular surface of the tibia, thus increasing stability of the joint.
  • To act as shock absorbers by increasing surface area to further dissipate forces

Question 3

cartilage - types

Answer 3

• There are three types of cartilage tissue in the body:
  1. Hyaline –> most abundant, spherical chondrocytes, only have fine collagen fibers (type2) and examples are articular cartilages (cover bone ends in joints), costal cartilages (connects ribs to sternum), respiratory cartilages and nasal cartilages
  2. Elastic –> contain stretchy fibers and are found in the external ear and epiglottis
  3. Fibrocartilage –> highly compressible with great tensile strength, thick collagen fibers (type 1), found in the menisci of the knees and discs between vertebrae

Question 4

articulate cartilage - structure

Answer 4

• All three types have the same basic components—cells called chondrocytes, encased in small cavities (lacunae) within an extracellular matrix containing a jellylike ground substance and fibers.
• Cartilage is covered in perichondrium (connective tissue) and has no nerves or blood vessels  depend on diffusion
• Between collagen (type 2) fibril we find proteoglycans which have a negative charge which attracts salts (calcium) which then attract water
  • High pressure water –> absorb forces/loads

Question 5

osteoarthitis pathology

Answer 5

• Mechanical wear of joints, an active disease process in the articular cartilage that ultimately affects the entire joint
• Holes in the articulate cartilage (bone exposure)
• Damage to ligaments and osteophytes (bone outgrowth, repair mechanism attempts to repair cartilage loss but results in bony outgrowths)
• Subchondral microdamage
• Bone tissue where there should be cartilage (sub-chondral)
• Besides just bone and cartilage dysfunction all other tissue types in the joint are affected:
  • Inflamed synovium
  • Synovial fluid dysfunction (reduced viscosity)
  • Cracked meniscus (ligament damage)
  • Weak tendons
• Cartilage cells become activated and start to secrete matrix-degrading enzymes, increased mineralisation (collagen type x) and release inflammatory cytokines
• Treatment starts with pain relieve and later joint replacement surgery (every 15 years)

Question 6

progression of OA

Answer 6

• Cartilage homeostasis is normally kept until trauma occurs
• Certain factors influence whether the trauma develops into OA (age, weight, genetics, etc.)
• The trauma causes repetitive loading onto underdeveloped cartilage which can turn into a vicious cycle of damage and misloading of cartilage
  1. The first thing that happens is breakdown of proteoglycans due to high load
  2. Less water is in the cartilage  less pressure
  3. Collagen (type 2) fibrils are no longer arranged nicely
  4. Chondrocytes become overactive and start secreting matrix-degrading enzymes etc.
  5. Cycle…
• Often ACL injury causes unstable knee joints which leads to a shift in the loading within the knee to weaker parts of cartilage which can set the cycle in first gear

Question 7

external knee adduction moment and OA

Answer 7

• The GRF goes up from the foot to the COM which causes a moment arm to form at the knee joint –> EKAM
• This moment arm causes more force to be on the medial side of the joint  more prone to OA
• In OA the medial side of the knee often caves in forming an even larger moment arm and more pressure on the medial side of the joint

Question 8

treatment plan for OA

Answer 8

1. weightloss, physical therapy, bracing and spliting
2. pain relief: acetomiophin
3. NSAIDs
4. glucosamine and chondroitin to slow progression
5. pain relief: opioids
6. corticosteroid injections (exacerbations)
7. hyaluronic acid injection
8. joint replacement

Question 9

cartilage repair surgery

Answer 9

• Microfracture involve disrupting the subchondral bone integrity to create channels between the defect in the cartilage and underlying bone marrow
  • The recruitment of multi-potent marrow stromal cells to the defect through these channels leads to subsequent formation of tissue resembling articular cartilage.
  • However, this approach is only effective for small defects
• Another surgical procedure (mosaicplasty) involves the replacement of the lost cartilage with tissue grafts, i.e., an osteochondral allograft or autologous transplant harvested from the patient’s own cartilage
  • Small cylindrical plugs taken from non-weight-bearing areas are fitted into the defect
• Adoptive cell transfer

Question 10

gait modifying therapy

Answer 10

• OA patients often have large EKAM due to caving in of medial knee joint
  • five basic gait modifications have been shown to reduce the adduction torque in patients with knee OA:
  1. toeing out
  2. walking more slowly
  3. walking with decreased stride length
  4. walking with increased medial-lateral trunk sway

Question 11

stages of cartilage diagnosis

Answer 11

1. defect
   - type of lesion
   - location of lesion
   - size
   - age
2. joint
   - previous injuries
   - instability
   - inflammation
3. lower leg
   - leg alignmnet (varus/valgus)
4. patient
   - BMI
   - age
   - activity