Osteoarthritis Diagnostics

Laboratory Tests and Ancillaries

Laboratory tests are usually normal; however, laboratory results are not reliable nor required in establishing the diagnosis of osteoarthritis.  

They may help exclude other diagnoses and monitor the side effects of medications. One should consider obtaining a complete blood count (CBC), liver function test (LFT), and creatinine (Cr) level before starting therapy with nonsteroidal anti-inflammatory drugs (NSAIDs), especially in the elderly and in patients with other chronic illnesses.  

Aspiration of synovial fluid may be done to exclude other diagnoses such as septic arthritis, gout, and pseudogout. This would usually reveal clear, viscous fluid with a leukocyte count of <2,000/mm³.

Imaging

Imaging assists in diagnosing osteoarthritis. It is suggested for patients ≥45 years old, with joint pain especially at movement, and with morning stiffness lasting for >30 minutes. 

Plain X-rays  

Plain X-rays are the primary imaging method used to confirm the diagnosis of osteoarthritis, stage its severity, and follow its progression. The severity of radiographic findings does not correlate well with the severity of the symptoms or the presence of the functional disability, and the absence of radiologic features does not exclude osteoarthritis. It may also be used to exclude other diagnoses (eg trauma).  

Plain X-rays are almost always sufficient in diagnosing osteoarthritis. The radiologic features indicative of osteoarthritis but may not be observed in early disease include joint space narrowing which is often irregular or asymmetric, subchondral sclerosis which appears as an increased density in subchondral bone, bony proliferation with the presence of osteophytes or spurs, cysts in subchondral marrow adjacent to or sometimes remote from the joint which is usually seen in late cases, and soft tissue changes (eg small effusions, calcification, and soft tissue swelling).  

It is taken in standing anteroposterior (AP) and lateral positions and should be interpreted together with the patient’s clinical presentation.

Magnetic Resonance Imaging (MRI)  

MRI is used to study joints, cartilage, subchondral bone, and synovial tissue simultaneously. It may be useful in studying the secondary causes of osteoarthritis (ie meniscal tear, previous ligament injury) or identifying any intraarticular loose body.  

Ultrasound  

Ultrasound may be useful in investigating joint structure alterations and guiding intra-articular steroid injections; however, it should not be used routinely.