1. and
present
The pathophysiology of osteoarthritisThe pathophysiology of osteoarthritis

2. A few useful definitions and reminders
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.
 Osteoarthritis is characterised by cartilage loss combined with synovial tissue
thickening and subchondral bone osteosclerosis
 Other than the spine, osteoarthritis most commonly affects the knees, hands and hips
 Osteoarthritis is a common complex disorder with multiple hereditary, constitutional
and environmental risk factors
 Cartilage degeneration is not simply an age-related process, osteoarthritis is an
individual disease entity and has both inflammatory and mechanical features.
 Obesity increases the risk of osteoarthritis in the legs and fingers
2
Spine Knee Hands Hip

3. 3
Hip-femoral osteoarthritis. Right
hip arthrography, frontal image.
Cervical spine. T2 MRI.
Internal and external femorotibial
osteoarthritis. Knee CT-arthrography.
MRI of the left hand, T2 weighted sequences,
coronal image after saturation of the fat signal.

4. Cartilage and chondrocyte
Cartilage is a very specific type of dense connective tissue
 Non vascularised: it draws its nutrients by a process of diffusion
from the synovial fluid secreted by the synovial membrane and
the subchondral bone.
 Not innervated: it cannot therefore be held directly responsible
for the pain experienced by osteoarthritis sufferers
 Cartilage consists of a single type of cell, chondrocytes,
embedded in the matrix they create
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp
Under normal conditions, chondrocytes have low metabolic activity which
is mainly confined to breaking down various elements in the matrix
(proteoglycans and collagen) and to renewing these same matrix components
4
Healthy knee cartilage

5. Osteoarthritis: a separate disease entity
 Osteoarthritis is not simply the result of normal ageing and excessive
pressure on a joint
 It is caused by a variety of factors:
 Local, mechanical factors
 General (heriditary) and systemic factors (e.g. adipokines)
 And in some cases, trauma
 It involves changes in all joint tissues: cartilage, the subchondral bone
(which could play an even more important role in this
pathophysiology), the articular capsule and the synovial membrane
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.5

6. Osteoarthritis: the disease process (1)
 Excessive pressure on the cartilage:
 Chondrocytes are activated via pressure-sensitive
membrane receptors (mechanoreceptors)
 Inflammation mediators are released
 The cartilage matrix deteriorates
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.
6

7.  The 3 features in osteoarthritis are:
 Degradation of the cartilage matrix
 Inflammatory reaction in the synovial
membrane, often accompanied by joint
effusion
 Reaction in the subchondral bone with
proliferation of neosynthesised bone:
osteophytes (hypertrophic formation)
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.
7
Osteoarthritis: the disease process (2)
Shoulder osteoarthritis with
moderate gleno-humeral joint space
narrowing and osteophyte on the
lower surface of the humeral head.
Knee osteoarthritis, tibial edema
and synovial inflammation. FSE T2
sagittal slices.

8. Mechanical osteoarthritis
 Excessive weight: obesity or frequent heavy
load-bearing (workplace or sport [e.g.
football, weight-lifting])
 Joint overload and repeated microtrauma
 Unevenly distributed pressure: dysplasia,
meniscectomy, malalignement (genu varum
or genu valgum)
 Knee instability: ligament hypermobility,
cruciate ligament rupture, particularly of the
anterior ligament, or a poorly managed
sprain, etc.
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp8
Subchondral cyst under the insertion of
the posterior cruciate ligament. FSE T2
sequence in sagittal plane.
Some cases of osteoarthritis are mainly
mechanical in origin (caused by excessive
pressure on part or all of the joint):

9. Secondary osteoarthritis
 Diseases directly affecting the cartilage: for example:
crystalline particles in the cartilage - urate crystals (gout)
or calcium deposits (chondrocalcinosis); genetic
hemochromatosis; ochronosis (very rare); and genetic
disorders which weaken the structures in the cartilage
(proteoglycans or collagen)
 Disease affecting other joint tissues with an indirect
impact on the cartilage, especially:
 disorders of the subchondral bone, such as aseptic
osteonecrosis,
 synovial membrane disorders, joint infections even once cured,
or synovial inflammation, for instance rheumatoid arthritis
Société Française de rhumatologie website:
http://www.rhumatologie.asso.fr/04-Rhumatismes/grandes-maladies/0B-dossier-arthrose/A0_definition.asp9
Osteonecrosis of the femoral
head in a patient with hip
osteoarthritis.

10. Osteoarthritis and Obesity
 Obesity is a predisposing factor for osteoarthritis:
 via mechanical constraints linked to excess weight which
trigger chondrocyte activation (see following slides, 10 and 11)
 and no doubt also through the production of cytokines in the
fatty tissue which enter the bloodstream and have an effect
on the joint tissues. This could explain the higher incidence of
finger osteoarthritis in obese patients
 This is best illustrated by osteoarthritis of the fingers,
which is more common in overweight or obese patients
 The risk of knee osteoarthritis increases by 15% for every
point increase in the BMI
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.10
Frontal image of advanced
patellofemoral knee
osteoarthritis.

11. Osteoarthritis and fatty tissue
 Fatty tissue, particularly abdominal fat, plays a role
in systemic inflammation by secreting specific cytokines
called adipokines (adiponectin, leptin and resistin)
 Adipokines have potent immunomodulating effects and
are found in the synovial fluid of patients with
osteoarthritis
 The Hoffa fat pad, located immediately behind the patellar
tendon, may also produce adipokines. These adipokines
can migrate directly into the synovial fluid
11
Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.

12. A new concept: "metabolic osteoarthritis"
The concept of metabolic osteoarthritis emerged after
the following were observed:
 There is an epidemiological link between
osteoarthritis and type 2 diabetes and
between osteoarthritis and metabolic
syndrome or each of its individual
components (abdominal obesity,
hyperglycemia and dyslipidemia)
 The incidence of knee osteoarthritis is higher
in obese patients concomitantly presenting
with one or more features of metabolic
syndrome
Therefore, younger patients with osteoarthritis should be screened for a
cardiometabolic disease (metabolic syndrome or type 2 diabetes)
12 Sellam J, Berenbaum F. Arthrose et Obésité. Rev Prat 2012;62:621-629.
The concept of metabolic osteoarthritis
(according to Sellam 2012)

13. Knee osteoarthritis and trauma
 In addition to age and excess weight, the risk
factors for knee osteoarthritis which must also be
taken into consideration include trauma,
particularly:
 Meniscus injury
 Anterior cruciate ligament rupture, causing anterior
knee placing undue mechanical stress
on the medial tibio-femoral compartment and causing
premature wear
 Joint fracture
 Prevention:
 The most conservative possible treatment of
meniscus injury, given the increased risk of knee
osteoarthritis after meniscectomy, therefore in this
case, no meniscectomy after the age of 40
 Surgical repair of the ACL will not prevent the
subsequent development of osteoarthritis
13 La Revue du Praticien 2012; 62: 621-629, Situations à risque d’arthrose du genou. Charles-Henri Flouzat-Lachaniette.
Bilateral femorotibial knee
osteoarthritis. Arthrography.

14. Osteoarthritis and physical exercise
 When repeatedly exposed to extreme stress, the knee may
develop osteoarthritis
 Professions at higher risk of knee osteoarthritis: mainly
construction workers who often work in a crouched position
or kneeling (knee hyperflexion, leading to meniscal injury and
osteoarthritis)
 Sport and osteoarthritis: moderate physical exercise does not
increase the risk of osteoarthritis. Intense sporting activity can
increase this risk through injury (joint fractures and meniscal
or ligament injury) and repeated microtrauma
14 La Revue du Praticien 2012; 62: 621-629, Situations à risque d’arthrose du genou. Charles-Henri Flouzat-Lachaniette.

15. CONCLUSION
 Osteoarthritis is not a simple age-related disease
caused by wear and tear on weight-bearing joints.
It is characterised by low-grade tissue inflammation
 It is a disorder with a demonstrated systemic
component in some forms, potentially involving the
fatty tissue and the adipokines it secretes
 The main risk factors are age, obesity
and repeated microtrauma
15
Femorotibial and patellar
knee osteoarthritis.
Arthrography.