Differential Diagnosis of Osteoarthritis

The differential diagnosis of osteoarthritis focuses on characteristics that set it apart from other types of arthritis. While most people know that osteoarthritis is the most common type of arthritis, what distinguishes it from other types?

Common Signs, Symptoms, and Characteristics of Osteoarthritis

The signs and symptoms of osteoarthritis are considered first. The primary signs and symptoms include joint pain, joint stiffness, and restricted range of motion of the affected joint or joints. With osteoarthritis, typically, one (monoarthritis) or just a few joints are affected. Most newly-diagnosed osteoarthritis patients are middle-aged or older. Other common characteristics associated with osteoarthritis include:

• Osteoarthritis pain typically worsens with activity or joint use and improves with rest.
• Accordingly, osteoarthritis pain is usually worse in the late afternoon or early evening. In some people, though, stiffness and pain may be worse in the morning.
• Severe osteoarthritis may be associated with night pain and sleep disruption.
• Usually, osteoarthritis pain is most intense over the joint. Certain joints, as well as periarticular soft tissue lesions, may cause pain away from the joint line. That said, tenderness along the joint line is characteristic of joint issues, whereas tenderness away from the joint line is more typical of periarticular soft tissue disease.
• Limited range of motion associated with arthritis is usually associated with osteophyte formation, thickening of the joint capsule, joint effusion, and synovial thickening. This pertains to both active and passive range of motion.
• Bony swelling may occur and is indicative of bone and cartilage remodeling on either side of the affected joint.
• Joint deformity is a sign of advanced osteoarthritis.
• Joint instability, such as locking, giving out or buckling, is a common sign of knee osteoarthritis.
• Specific joint involvement may point to osteoarthritis. The joints that are commonly affected by osteoarthritis include the knees, hips, interphalangeal joints of the hand, the first carpometacarpal joints, the first metatarsophalangeal joints, and the facet joints of the lower cervical and lower lumbar spine. Joints that are less commonly affected by osteoarthritis include the elbow, wrist, shoulder, and ankle.

Differentiating Osteoarthritis From Other Conditions

While we have highlighted the common characteristics of osteoarthritis, there is obvious overlap with other types of arthritis. A definitive diagnosis depends on distinguishing osteoarthritis from those other types of arthritis. The specific joints involved, as well as the presence or lack of certain systemic symptoms (fatigue, weight loss, lack of appetite, fever, malaise), are primarily what is considered to distinguish or differentiate osteoarthritis.

Osteoarthritis Versus Rheumatoid Arthritis

Osteoarthritis may initially be confused with rheumatoid arthritis if there is hand involvement. Very distinct patterns of finger joint involvement can differentiate between the two types of arthritis relatively easily. Osteoarthritis of the hand typically affects the distal interphalangeal joints.

The presence of Heberden's nodes is also characteristic of osteoarthritis, but not of rheumatoid arthritis. Rather than distal interphalangeal involvement, there is proximal interphalangeal joint involvement with rheumatoid arthritis. Swelling is characteristically different: bony and firm with osteoarthritis versus softer and tender with rheumatoid arthritis. Stiffness is also characteristically different: morning stiffness is the main feature of rheumatoid arthritis versus evening stiffness following a day of activity, which is more characteristic of osteoarthritis.

X-ray findings for osteoarthritis are distinctive as there is joint space narrowing from the cartilage loss and osteophyte formation that is common. With regard to blood tests, a positive rheumatoid factor test, elevated sed rate, and the presence of anti-CCP would all point to rheumatoid arthritis versus osteoarthritis.

Osteoarthritis Versus Psoriatic Arthritis

Both osteoarthritis and psoriatic arthritis often involve the distal interphalangeal joints of the hand. The distinguishing feature is that, with psoriatic arthritis affecting these joints, there is usually fingernail abnormalities (e.g., pits, ridges). Also, with psoriatic arthritis, there is dactylitis (sausage-like appearance of the affected fingers).

Osteoarthritis Versus Gout or Pseudogout

Like osteoarthritis, gout or pseudogout may begin as monoarthritis and develop into polyarticular arthritis. The distinguishing feature of gout or pseudogout is episodes of intense inflammation and pain of a single or few joints. The presence of crystals in the joint also distinguishes gout or pseudogout. There are no crystals associated with osteoarthritis. Gout is specifically associated with uric acid crystals, while pseudogout is associated with calcium pyrophosphate crystals.

Osteoarthritis Versus Hemochromatosis

Initially, joint pain caused by iron overload can be mistaken for osteoarthritis. Hemochromatosis mostly affects the metacarpophalangeal joints and wrists, however. Very specific X-ray findings also are characteristic of hemochromatosis, helping to differentiate the two conditions.

Osteoarthritis Versus Infectious Arthritis

If the initial onset of osteoarthritis is as an acute painful episode of synovitis in one joint, rather than its usual non-inflammatory onset, it may be mistakenly attributed to an infection. Various laboratory tests would be used to identify or rule out the infection.

Osteoarthritis Versus Various Soft Tissue Diseases

There are various soft tissue abnormalities that can develop around a single joint, and because it initially seems related to a single joint, osteoarthritis may be suspect. This may involve tendonitis, bursitis, enthesitis, muscle strain, or various related syndromes. MRI imaging may be utilized to identify the actual source of the problem.

A Word From Verywell

According to the Centers for Disease Control and Prevention (CDC), more than 30 million US adults have osteoarthritis. While it is the most common type of arthritis, osteoarthritis is sometimes confused with other types of arthritis—especially early on and especially the types that affect one joint (monoarthritis) or a few joints. It is very important for doctors to do a differential diagnosis and accurately diagnose the disease. Proper treatment depends on an accurate diagnosis. That's precisely why differential diagnosis is important and why you need to know what type of arthritis you have.