Distinguishing Arthritis and Low Back Pain Conditions

A vital diagnostic clue is the duration of morning stiffness; in OA, this stiffness typically lasts less than 30 minutes. On physical examination, clinicians may observe crepitus (a grinding sensation) and palpable osteophytes (bone spurs).

Rheumatoid Arthritis (RA)

Rheumatoid Arthritis is an autoimmune disease where the immune system targets the synovium (the lining of the joint). It is distinguished from OA by being polyarticular and symmetrical, meaning it often affects the same joints on both sides of the body. It primarily targets the small joints of the hands and feet and typically peaks in patients between ages 35 and 50.

A key differentiator is that morning stiffness in RA lasts more than 30 minutes. Because it is systemic, patients may also experience fatigue or other non-joint symptoms.

Mechanical and Neurological Low Back Pain

Low back pain presentations can be categorized by whether the pain is localized to musculoskeletal structures or if it involves the nervous system.

Mechanical Low Back Pain

Mechanical low back pain arises from the musculoskeletal structures of the back, such as muscles, ligaments, or discs. The pain is typically described as back-dominant, deep, achy, and poorly localized. While patients may experience referred pain in the gluteal region, it does not follow a specific nerve path. Crucially, mechanical pain is characterized by the absence of neurological signs: there is no sensory loss, no motor loss, and the Straight Leg Raise (SLR) test is negative.

Radicular Pain vs. Radiculopathy

When pain involves the spinal nerve roots, clinicians must distinguish between "sensitization" and "impairment of function."

1. Lumbar Radicular Pain: This is neurogenic pain caused by the sensitization or inflammation of a nerve root. It is leg-dominant and presents as sharp, "electric," or shooting pain that follows a specific dermatomal pattern (the area of skin supplied by a single spinal nerve). While the patient may feel numbness or paresthesia, there are no objective neurological deficits.
2. Lumbar Radiculopathy: This refers to actual impaired function of the nerve root. It is distinguished from radicular pain by the presence of objective clinical findings: sensory loss, motor weakness (loss of strength in a myotome), and impaired or diminished reflexes.

Exam Tip: When assessing for radiculopathy, always check for "objective" signs. If the patient says their leg is weak, but you find no motor loss or diminished reflexes on exam, you are likely looking at radicular pain rather than radiculopathy.

Neurogenic Claudication and Spinal Stenosis

In older adults (typically over 60), intermittent leg pain and weakness may be caused by spinal stenosis—a narrowing of the space within the spinal canal. This results in neurogenic claudication, where the patient experiences buttock and leg pain that compromises their walking ability.

A classic clinical indicator is the "shopping cart sign": symptoms are often relieved or improved by forward flexion (leaning forward), as this position increases the space available for the nerves. Unlike vascular claudication, which is relieved by simply standing still, neurogenic claudication often requires a change in posture to find relief.

Summary Table of Key Distinctions