Sudden, severe pain that develops within a few minutes

Blockage of an artery in a limb, usually a leg, by a blood clot

Sudden, severe pain

Coolness and paleness of the limb

After several hours, signs of nerve malfunction, such as weakness, numbness, tingling, or cramping

Weak or no pulse felt in the limb

Arteriography done immediately

Sudden herniation of a disk in the spine

Pain and sometimes numbness that occurs in a line down the limb

Pain that is often worsened by movement

Often neck or back pain

Sometimes weakness in part of the affected limb

Usually MRI

Heart attack (myocardial infarction)

Pain in an arm, not a leg

Sometimes pain or pressure in the chest or jaw

Sometimes nausea, sweating, and shortness of breath

Sometimes in people known to have heart disease

ECG

Blood tests for substances that indicate heart damage (cardiac markers)

Sometimes angiography of the arteries of the heart

Fatty deposits in artery walls (atherosclerosis), which reduce blood flow, almost always in a leg

Intermittent episodes of leg pain that occur only when walking and are relieved by a few minutes of rest (intermittent claudication)

Ultrasonography

Sometimes arteriography

Pain that develops gradually (over hours to days)

Bacterial infection of the skin (cellulitis)

An irregular area of redness, warmth, and tenderness

Sometimes fever

A doctor's examination

Sometimes blood cultures

Deep vein thrombosis (a blood clot in a deep-lying vein in a leg [typically] or an arm)

Swelling of an entire part of a limb (for example, whole calf or calf and upper leg)

Usually pain, redness, warmth, and/or tenderness in the affected area

Sometimes in people with risk factors for blood clots, such as recent surgery, an injury, bed rest, a cast on a leg, use of hormone therapy, or cancer

Ultrasonography

Sometimes a blood test to detect blood clots (D-dimer)

Bacterial infection deep under the skin and/or in the muscle (myonecrosis)

Deep, constant pain

Redness, warmth, tenderness, and swelling that feels tight

Signs of severe illness (such as fever, confusion, and a rapid heart rate)

Sometimes a foul discharge, blisters, or areas of blackened, dead skin

Blood and tissue cultures

X-rays

Sometimes MRI

Bone infection (osteomyelitis)

Deep, constant pain that often occurs at night

Bone tenderness and fever

Often in people with risk factors (such as a weakened immune system, use of injection drugs, or a known source for the infection)

X-rays and MRI and/or CT

Sometimes bone culture

Chronic pain (present for a week or more)

A bone tumor (originating in the bone or spread to the bone from cancer elsewhere in the body)

Deep, constant pain that is often worse at night

Bone tenderness

Often in people known to have cancer

X-rays and MRI and/or CT

Pressure on certain nerves, as occurs in

• A disorder of the brachial plexus (a network of nerves in the shoulder and back)

• Thoracic outlet syndrome (which involves compression of nerves or blood vessels that pass between the neck and chest)

Usually weakness and sometimes numbness or tingling along part of the limb

Sometimes only a doctor's examination

Sometimes electromyography and nerve conduction studies

Sometimes MRI

Pressure on a spinal nerve root (the part of a spinal nerve next to the spinal cord), which may be caused by a herniated disk or bone spurs

Pain and sometimes numbness that occurs in a line down the limb

Pain that is often worsened by movement

Often neck or back pain

Often weakness in part of the affected limb

Usually MRI

Degeneration or inflammation of many nerves throughout the body (polyneuropathy)

Chronic numbness and burning pain, typically in both hands and/or both feet

Often in people with a disorder that causes nerve damage, such as diabetes, alcohol use disorder, or vasculitis

Sometimes only a doctor's examination

Sometimes blood tests or electromyography and nerve conduction tests

Complex regional pain syndrome

Severe burning or aching pain

Sometimes increased sensation and pain caused by something that would not ordinarily be considered painful

Often skin that appears red, mottled, or ashen and increased or decreased sweating in the affected limb

Typically in people who have had an injury (sometimes many years before)

Only a doctor's examination

Chronic venous insufficiency (causing blood to pool in the legs)

Swelling of the ankles or legs

Chronic mild discomfort, aching, or cramps in the legs but no pain

Sometimes reddish brown, leathery areas on the skin and shallow sores on the lower legs

Often varicose veins

Only a doctor's examination