Diagnosis and clinical features of osteoarthritis
The diagnosis of osteoarthritis is largely based on clinical assessment—laboratory investigations or imaging are rarely indicated. Clinical assessment should include a thorough history, physical examination, and functional and psychosocial assessment.
The major symptoms and signs of osteoarthritis are pain, stiffness and swelling, which can lead to impaired mobility and physical function (eg a patient may not be able to bend down and put their shoes on).
In early osteoarthritis, pain typically has an insidious onset. It tends to be localised to the affected joint, dull and aching in nature, made worse with activity and relieved with rest. As the disease advances, pain can become more widespread and can also occur at rest.
Stiffness may occur after inactivity or in the morning, but is usually of short duration (less than 30 minutes).
The joint swelling in osteoarthritis is typically bony (hard) due to osteophyte formation. At times there may also be spongy (soft) swelling present due to a coexisting joint effusion or synovial thickening. If present, soft-tissue swelling in osteoarthritis is usually not as significant as that observed in inflammatory arthritis.
Physical examination should identify:
- the specific joints affected
- the presence of inflammation (swelling)
- the degree of joint disruption (crepitus, restricted or painful movement, instability)
- any associated muscle weakness.
Radiological findings alone (eg asymmetric loss of joint space, subchondral sclerosis, osteophytes, bone cysts) should not be used to diagnose osteoarthritis because they correlate poorly with symptoms and do not change the management approach. Imaging is not required in patients with a typical clinical presentation who do not have alerting features. A plain X-ray should; however, be performed in patients with atypical presentations to exclude other diagnoses. Further advice on the role of imaging is included in the Australian Clinical Care Standards for Knee Osteoarthritis.
Laboratory investigations are usually not required for the diagnosis of osteoarthritis, and inflammatory markers are usually normal. For patients presenting with joint swelling, a joint aspiration may be useful to excluding other pathologies (eg gout). In osteoarthritis the synovial fluid white cell count is typically less than 1000 x 106/L.