**2. Standard methods of detection**

Osteoarthritis is a condition affecting a multitude of tissues within a joint, and as such, approaches which give information to the clinician on bone, muscle, cartilaginous tissue and the microenvironment within a joint are required to give a full picture of the condition of a joint. Imaging is currently the main diagnostic tool used to assess osteoarthritis. Dependent upon the form of imaging used, a variety of tissues can be examined as markers of disease state and progression.

In clinical practice, a combination of clinical presentation and X-radiography (X-ray) is used to diagnose osteoarthritis. When a patient presents as over 45 years of age, with typical symptoms of osteoarthritis including pain within the joint during activity and minimal stiffness within the joint in the morning lasting no more than 30 min, then X-ray is not indicated for diagnosis [9, 17].

However, X-ray is useful when differential diagnosis is possible, and in certain scenarios, magnetic resonance imaging is used to give additional information on damage to tissues within the joint and inform treatment options.

**33**

**Table 1.**

*Acoustic Monitoring of Joint Health*

**2.1 X-radiography**

easily examined.

*DOI: http://dx.doi.org/10.5772/intechopen.92868*

at different KL grades can be seen in **Table 1**.

the scale in the assessment of the knee joint.

symptomatic progression may have occurred [20].

**Grade Description of radiographic findings** 0 No evidence of radiographic osteoarthritis

*Kellgren-Lawrence scale description of radiographic findings.*

bone contour

1 Doubtful narrowing of the joint space and possible osteophytic lipping 2 Definite osteophytes and possible narrowing of the joint space

with sclerotic walls and possible deformity of bone contour

underlying the disease.

X-ray works upon the principle of differential absorbance of radiation by different tissues, with dense tissues such as the bone absorbing a large proportion of the radiation compared to soft tissues such as the muscle and connective tissue. As a result, the bone appears bright white on images and can be studied for changes in morphology, whereas soft tissues show less differentiation and are not

The current gold standard in the diagnosis of osteoarthritis from radiographic images involves the scoring of X-ray images using the Kellgren-Lawrence (KL) scale. The Kellgren-Lawrence is a five-point scale which categorises disease severity based upon the assessment of bony changes, appearances of osteophytes and joint space narrowing within the joint [18]. The description of the radiographic findings

The KL scale was first described in 1957 in response to an identified need to standardise the definition of changes within an osteoarthritic joint in order to improve inter-rater reliability when reporting the disease [18]. Thorough analysis of the performance of the scale at joints throughout the body revealed that whilst correlation between the defined changes and osteoarthritis were observed at all joints bars the wrist, the greatest inter-rater agreement was found within the knee joint. Intra-rater repeatability followed a similar trend with slightly better agreement between readings. This has subsequently been reflected in the most common use of

More recent comparison of radiographic scoring systems has established that for the knee joint, the KL scale has stood the test of time, with no subsequently developed grading systems outperforming the inter-rater repeatability of this scale [19]. However, whilst the limit of inter and intra-observer reliability in assessing radiographic osteoarthritis may have been reached (correlation coefficients around 0.8), it is acknowledged that a more diverse manner of assessment of osteoarthritis may be warranted to improve sensitivity when assessing disease progression and specificity for aspects of the homogeneous pathophysiology

In terms of sensitivity, KL scoring of radiographs does not perform well in the detection of early disease or in the monitoring of disease progression, where large time periods are required to observe a change in category during which time

Alone, radiographic assessment using the Kellgren-Lawrence scale allows direct assessment of bony changes such as osteophyte formation, however, relies on indirect measures of joint space narrowing to assess cartilaginous change. The surrogate marker of joint space narrowing in place of direct measurement of cartilage, whilst

3 Moderate multiple osteophytes, definite narrowing of the joint space, small pseudocystic areas

4 Large osteophytes, marked narrowing of joint space, sever sclerosis and definite deformity of
