Using joint-space narrowing as a measure of structural change is dependent on the accuracy of X-ray measurement, not an easily achievable goal. In the past, standing X-rays have been routinely used in study performance. It has been subsequently shown that more accurate definition of joint-space responses can be made using special positioning techniques which involve semiflexed knee positions.18 In an upright position, the joint space appears wider than when studied in a semiflexed position.
As noted, osteoarthritis is a disease not only of cartilage but also of other joint tissues. Accordingly, MRI measures which investigate the whole joint (so called WORMS) are important in designing structure-modification studies.17
Biomarkers
There is a great deal of interest in using biomarkers found in the serum and urine to provide earlier clues to structural disease changes, particularly as they relate to therapeutic responses to disease-modifying agents.18 At this time, biomarkers have limited effectiveness for assessing disease modification. Biomarker assessment is complicated by the fact that osteoarthritis is frequently multi-articular. A given patient may have early as well as late osteoarthritis in various joints, so a biomarker to identify OA responses in one specific joint will be confounded by biomarker responses related to other joints with OA not being assessed. C-telopeptide-II, a biomarker measuring type-II collagen breakdown, seems be the most promising of these biomarkers.
Markers of inflammation including hyaluronans and C-reactive protein may help identify patients more likely to have increased rates of disease progression, based on studies demonstrating a positive correlation. This may be because these are measures of inflammation, which is associated with more severe and rapid disease advancement.
Surgical Approaches
Partial or total joint replacement, particularly in the knee or hip, is recognized as a major advance in decreasing pain and increasing quality of life in patients with late-stage osteoarthritis. New procedures, including minimally invasive techniques and uni-compartmental replacement rather than total knee replacement, represent additional improvements offering faster rehabilitation and fewer complications. Surface replacement in the hip in carefully selected patients allows maintenance of bone stock and increases opportunities for additional therapeutic alternatives if future surgery is required.
Conclusion
We know a great deal more about OA etiopathogenesis and treatment than we did even a short time ago. The therapeutic advances have not, unfortunately, been as striking as those that have occurred over the past decade in the management of RA. Advances in our knowledge of disease pathophysiology, however, auger well that agents capable of better and safer symptomatic control and disease modification will be forthcoming.
