Imaging in Osteoarthritis Dr Matt Chamberlain Sports & Exercise Medicine Registrar MP Sports Physicians

Imaging in Osteoarthritis Major focus on knee Imaging types: X-ray MRI Newer MRI modalities

Why image in Osteoarthritis? Diagnosis Staging Prognosis Efficacy of Treatment Follow-up

X-ray Simplest imaging technique First Line Can detect OA-associated bony features: Marginal osteophytes Subchondral sclerosis Subchondral cysts. Joint space width (JSW) - an indirect surrogate of cartilage thickness and meniscal integrity. Joint space narrowing (JSN) is the key end point currently for interventional studies

X-ray Correlations Correlation between x-ray and symptoms is variable: Knee x-ray correlates with symptoms - 85% Hand and wrist x-ray correlates with symptoms - 80% Hip x-ray correlates with symptoms - 75%

X-ray Findings Non-uniform narrowing of joint space Subchondral bony sclerosis Marginal osteophyte formation Subchondral Cyst formation Gross deformity in advanced cases

Joint Space Narrowing

Marginal Osteophytes

Subchondral Sclerosis

Subchondral Cysts

Gross deformity/Malalignment

Kellgren-Lawrence (KL)grading system

Progression in Osteoarthritis

Progression in Osteoarthritis

To weight bear or not to weight bear? Rosenberg View:  A weightbearing PA with the knees flexed 45 degrees. Most sensitive view for tibiofemoral OA Can be positive if weightbearing AP is normal.

Weight bearing knee x-rays

Weight bearing ankle x-rays

Limitation of x-rays Images bone only (‘whole joint process’) Gives only indirect measure of chondral thickness/mensical integrity Insensitive to early change Insensitive to progression

MRI – why image? Not routine clinical initial assessment Not routine for follow up in OA Useful in abnormal clinical presentation (i.e. tumour/AVN) Very sensitive with early presentation of rheumatalogical diseases Particularly useful in early stage OA Mechanical intra-articular issues Visualisation of pathologies not detected on x-ray

MRI – why image? Different definitions of OA in X-ray criteria MRI studies have strongly associated pain with the presence of synovitis and BML (bone marrow lesions)

Focal chondral pathology

Focal Chondral Pathology

Meniscal Pathology

Synovitis

Bone Marrow Lesions (BMLs)

Mechanical Pathology

Extra-articular pathology

Special mention: Hip OA Hip – spherical structure Thin covering of articular cartilage More difficult assessment than the knee Other features seen: Labral changes/hypertrophy Paralabral cysts Loose bodies Dysplasia

Special mention: Hip OA

Special mention: Hip OA

Advances in MRI imaging Can we see changes in chondral pathology earlier? Predominantly research tools Two major areas of advance: Quantitative articular cartilage analysis Compositional MRI: dGEMRIC T1 rho T2 mapping

Quantitative Articular Cartilage Analysis High- resolution 3D imaging sequences Requires segmentation of the hyaline cartilage Allows measure of tissue dimensions: Cartilage Volume (VC) Cartilage Area (AC) Area of Subchondral Bone (tAB) Area of denuded Subchondral Bone (dAB)

Quantitative Articular Cartilage Analysis

Quantitative Articular Cartilage Analysis

Quantitative Articular Cartilage Analysis Interesting research tool Quantitative nature makes it powerful Found associations between: Weight gain and increased cartilage loss Weight loss and decreased cartilage loss High BMI/Leptin levels associated with cartilage loss Systemic bone/subchondral bone density and risk of progression

Compositional Imaging Cartilage consists of: 1-2% Chondrocytes 5-10% Proteoglycans (GAGs) 15-20% Type 2 Collagen 70-80% water

dGEMRIC MRI Assesses early chondral changes through GAG loss prior to macroscopic cartilage loss Uses intravenous/intra-articular gadolinium that repels GAGs With Less GAG in cartilage there is more contrast penetration

dGEMRIC MRI

T2-weighted mapping Describes the composition of hylaine cartilage on basis of collagen structure and hydration In healthy cartilage, T2 values increase from deep to superficial Based on anisotropy of collagen fibers running parallel to subchondral bone T2 values vary with age and with distance to subchondral bone

T2-weighted mapping

T2-weighted mapping