As osteoarthritis can cause pain, stiffness and limitations in the mobility of the joints, early diagnosis is very essential to decide the treatment plan. Physical examination, laboratory investigations and imaging tests are the options available for diagnosing osteoarthritis. Since this disease is hereditary, medical history and physical examination of the patient are important for diagnosis.
Medical history includes signs and symptoms, traumatic injuries, current or previous illness, allergies, family history and other medical conditions. In physical check-up of the patient, the doctor examines the affected joints for swelling, redness, warmth and also examines skin rashes, tender points and other body symptoms. Presence of Bouchard’s nodes, Heberden’s nodes and bunions of the feet resulting from enlargement of the joints due to spur formations play a significant role in diagnosing osteoarthritis.
Diagnosing osteoarthritis involves laboratory investigations and imaging tests. Some blood tests are performed to rule out other forms of arthritis and medical conditions. The tests like determination of Rheumatoid factor (RF) and human leukocyte antigen (HLA-DR1 and HLA-DR4) usually give negative results in osteoarthritis, while positive results in inflammatory arthritis like rheumatoid arthritis. Elevated levels of gout indicate possibility of gout. Besides this, raised levels of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) indicate the inflammatory arthritis and are generally normal in osteoarthritis.
In addition to these laboratory investigations, analysis of synovial fluid is also an important for diagnosing osteoarthritis. This fluid is aspirated from the joint through a needle and it is tested for viscosity, chemistry, overall appearance, blood cell counts and micro-organisms. In the synovial fluid aspirated from the affected joint, there is slightly increase in the number of WBCs. The synovial fluid of the patient with osteoarthritis contains various biochemical markers such as chondroitin sulfate, pyridinoline crosslinks and hyaluronic acid which represent breakdown and repair of cartilage as well as cytokines and other markers of inflammation. The fluid is tested for the presence of crystals to rule out gout.

Besides these laboratory investigations, the imaging tests like x-ray, CT (computerized tomography) and MRI (magnetic resonance imaging) scan contribute a lot in the diagnosis of osteoarthritis. Common x-rays findings in osteoarthritis are narrowing of joint space, formation of bony spurs and formation of cysts. Ultrasound is useful in imaging of soft-tissue structures and tendons related to joint. It also helps to demonstrate joint effusions behind the knee. Besides this, arthroscopy is a useful procedure to detect the damage and abnormalities in the cartilage and ligaments.
Bone scan or radionuclide scintigraphy is non-specific but sensitive method of detecting osteoarthritis. The changes which are not detectable on x-ray can be detected in scintigraphic imaging. Besides this, MRI scan is more sensitive and can be effectively used for imaging joint effusions, joint ligaments, bone defects and osteophytes. In addition to that, CT scan helps to detect fine details of cortical bone.