Acute limb ischaemia can occur in patients through all age groups. Patients that smoke and have diabetes mellitus are at a higher risk of developing acute limb ischaemia. Most cases involve people with atherosclerosis problems.

Symptoms of acute limb ischaemia include:

- Pain

- Pallor

- Paresthesias

- Perishingly cold

- Pulselessness

- Paralysis

These symptoms are called "the six P's'"; they are commonly mis-attributed to compartment syndrome. One more symptom would be the development of gangrene. Immediate medical attention should be sought with any of the symptoms.

In late stages, paresthesia is replaced by anesthesia due to death of nerve cells.

In some cases, gangrene can occur within six hours of ischaemia.

Reduced blood flow to the skin layers may result in mottling or uneven, patchy discoloration of the skin

Cardiac ischemia may be asymptomatic or may cause chest pain, known as angina pectoris. It occurs when the heart muscle, or myocardium, receives insufficient blood flow. This most frequently results from atherosclerosis, which is the long-term accumulation of cholesterol-rich plaques in the coronary arteries. Ischemic heart disease is the most common cause of death in most Western countries and a major cause of hospital admissions.

When a limb is ischemic in the non-acute (chronic) setting, the condition is alternatively called peripheral artery disease or critical limb ischemia, rather than ALI. In addition to limb ischemia, other organs can become ischemic, causing:

- Renal ischemia (nephric ischemia)

- Mesenteric ischemia

- Cerebral ischemia

- Cardiac ischemia

Early symptoms of an arterial embolism in the arms or legs appear as soon as there is ischemia of the tissue, even before any frank infarction has begun. Such symptoms may include:

A major presentation of diabetic "skeletal muscle infarction" is painful thigh or leg swelling.

One of the hallmarks of arterial claudication is that it occurs intermittently. It disappears after a very brief rest and the patient can start walking again until the pain recurs.

The following signs are general signs of atherosclerosis of the lower extremity arteries:

- cyanosis

- atrophic changes like loss of hair, shiny skin

- decreased temperature

- decreased pulse

- redness when limb is returned to a "dependent" position (part of Buerger's test)

All the "P"s

- Pallor increase

- Pulses decreased

- Perishing cold

- Pain

- Paraesthesia

- Paralysis

CT angiography would be helpful in differentiating occlusive from non-occlusive causes of mesenteric ischaemia.

Non-occlusive mesenteric ischemia occurs due to severe vasoconstriction of mesenteric vessels supplying the intestine. Acute abdominal pain is the only early acute symptom in those patients, which makes early diagnosis difficult.

The causes of internal carotid artery dissection can be broadly categorised into two classes: spontaneous or traumatic.

The signs and symptoms of carotid artery dissection may be divided into ischemic and non-ischemic categories:

"Non-ischemic signs and symptoms"

- Localised headache, particularly around one of the eyes.

- Neck pain

- Decreased pupil size with drooping of the upper eyelid (Horner syndrome)

- Pulsatile tinnitus

"Ischemic signs and symptoms"

- Temporary vision loss

- Ischemic stroke

A limb infarction is an area of tissue death of an arm or leg. It may cause "skeletal muscle infarction", avascular necrosis of bones, or necrosis of a part of or an entire limb.

Intermittent claudication (Latin: "claudicatio intermittens") is a symptom that describes muscle pain on mild exertion (ache, cramp, numbness or sense of fatigue), classically in the calf muscle, which occurs during exercise, such as walking, and is relieved by a short period of rest. It is classically associated with early-stage peripheral artery disease, and can progress to critical limb ischemia unless treated or risk factors are modified.

Claudication derives from the Latin verb "claudicare", "to limp".

Symptoms of cerebral infarction are determined by the parts of the brain affected. If the infarct is located in primary motor cortex, contralateral hemiparesis is said to occur. With brainstem localization, brainstem syndromes are typical: Wallenberg's syndrome, Weber's syndrome, Millard-Gubler syndrome, Benedikt syndrome or others.

Infarctions will result in weakness and loss of sensation on the opposite side of the body. Physical examination of the head area will reveal abnormal pupil dilation, light reaction and lack of eye movement on opposite side. If the infarction occurs on the left side brain, speech will be slurred. Reflexes may be aggravated as well.

There are various classification systems for a cerebral infarction.

- The Oxford Community Stroke Project classification (OCSP, also known as the Bamford or Oxford classification) relies primarily on the initial symptoms. Based on the extent of the symptoms, the stroke episode is classified as total anterior circulation infarct (TACI), partial anterior circulation infarct (PACI), lacunar infarct (LACI) or posterior circulation infarct (POCI). These four entities predict the extent of the stroke, the area of the brain affected, the underlying cause, and the prognosis.

- The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification is based on clinical symptoms as well as results of further investigations; on this basis, a stroke is classified as being due to (1) thrombosis or embolism due to atherosclerosis of a large artery, (2) embolism of cardiac origin, (3) occlusion of a small blood vessel, (4) other determined cause, (5) undetermined cause (two possible causes, no cause identified, or incomplete investigation).

Ischemia-reperfusion (IR) tissue injury is the resultant pathology from a combination of factors, including tissue hypoxia, followed by tissue damage associated with re-oxygenation. IR injury contributes to disease and mortality in a variety of pathologies, including myocardial infarction, ischemic stroke, acute kidney injury, trauma, circulatory arrest, sickle cell disease and sleep apnea. Whether resulting from traumatic vessel disruption, tourniquet application, or shock, the extremity is exposed to an enormous flux in vascular perfusion during a critical period of tissue repair and regeneration. The contribution of this ischemia and subsequent reperfusion on post-traumatic musculoskeletal tissues is unknown; however, it is likely that similar to cardiac and kidney tissue, IR significantly contributes to tissue fibrosis.

Blue toe syndrome is a situation that may reflect atherothrombotic microembolism, causing transient focal ischaemia, occasionally with minor apparent tissue loss, but without diffuse forefoot ischemia. The development of blue or violaceous toes can also occur with trauma, cold-induced injury, disorders producing generalized cyanosis, decreased arterial flow, impaired venous outflow, and abnormal circulating blood.

The terms "blue toe syndrome", "grey toe syndrome" and "purple toe syndrome" are sometimes used interchangeably.

Studies may include echocardiography, thoracic and abdominal CT or MRI, peripheral arterial run off imaging studies, hypercoagulopathy labs, and interrogation of syndromes that lead to peripheral vascular pathology.

Up to 50% of people with PAD may have no symptoms. Symptoms of PAD in the legs and feet are generally divided into 2 categories:

1. Intermittent claudication—pain in muscles when walking or using the affected muscles that is relieved by resting those muscles. This is due to the unmet oxygen demand in muscles with use in the setting of inadequate blood flow.

2. Critical limb ischemia, consisting of:

Medical signs of PAD in the legs, due to inadequate perfusion, include:

- Noticeable change in color – blueness, or in temperature (coolness) when compared to the other limb.

- Buerger's test can check for pallor on elevation of limb and redness (rubor) on a change to a sitting position, in an assessment of arterial sufficiency.

- Diminished hair and nail growth on affected limb and digits

PAD in other parts of the body depends on the organ affected. Renal artery stenosis can cause renovascular hypertension.

Carotid artery disease can cause strokes and transient ischemic attacks.

Hyperaemia, hyperæmia, or hyperemia (Greek ὑπέρ (hupér, "over") + αἷμα (haîma, “blood”)) is the increase of blood flow to different tissues in the body. It can have medical implications but is also a regulatory response, allowing change in blood supply to different tissues through vasodilation. Clinically, hyperaemia in tissues manifest as erythema (redness of the skin) because of the engorgement of vessels with oxygenated blood. Hyperaemia can also occur due to a fall in atmospheric pressure outside the body.

Serum lactate level is a proxy measure of tissue oxygenation. When tissues do not have adequate oxygen delivery (i.e., are ischemic), they revert to less efficient metabolic processes, producing lactic acid.

Myoglobin is released from damaged muscle, as in the case of ischemia.

Serum creatinine and BUN may be elevated in the setting of Acute Kidney Injury.

Classically, it is described in male patients as a triad of the following signs and symptoms:

1. claudication of the buttocks and thighs

2. absent or decreased femoral pulses

3. erectile dysfunction

This combination is known as Leriche syndrome. However, any number of symptoms may present, depending on the distribution and severity of the disease, such as muscle atrophy, slow wound healing in the legs, and critical limb ischemia.

Peripheral artery occlusive disease is commonly divided in the Fontaine stages, introduced by René Fontaine in 1954 for chronic limb ischemia:

- Stage I: Asymptomatic, incomplete blood vessel obstruction

- Stage II: Mild claudication pain in limb

- Stage III: Rest pain, mostly in the feet

- Stage IV: Necrosis and/or gangrene of the limb

A classification by the Society for Vascular Surgery and International Society of Cardiovascular Surgery (SVS/ISCVS), introduced in 1986 and revised in 1997 (and known as the Rutherford classification after the lead author, Robert B. Rutherford), consists of four grades and seven categories:

- Grade 0, Category 0: Asymptomatic

- Grade I, Category 1: Mild claudication

- Grade I, Category 2: Moderate claudication

- Grade I, Category 3: Severe claudication

- Grade II, Category 4: Rest pain

- Grade III, Category 5: Minor tissue loss; Ischemic ulceration not exceeding ulcer of the digits of the foot

- Grade IV, Category 6: Major tissue loss; Severe ischemic ulcers or frank gangrene

The TASC (and TASC II) classification suggested PAD treatment by severity of disease seen on angiogram. More recently classifications, such as the Society for Vascular Surgery "Wound, Ischemia and Foot Infection" (WIFI) classification, take into account that ischemia and angiographic disease patterns are not the only determinants of amputation risk.

Moderate to severe PAD in the area of Fontaine's stage III to IV, or Rutherford's category 4 to 5, presents limb threat (risk of limb loss) in the form of critical limb ischemia.

In medicine, aortoiliac occlusive disease, also known as Leriche's syndrome and Leriche syndrome, is a form of central artery disease involving the blockage of the abdominal aorta as it transitions into the common iliac arteries.

Typical signs and symptoms of a strain include pain, functional loss of the involved structure, muscle weakness, contusion, and localized inflammation. A strain can range from mild annoyance to very painful, depending on the extent of injury.

The clinical presentation of CST can be varied. Both acute, fulminant disease and indolent, subacute presentations have been reported in the literature.

The most common signs of CST are related to anatomical structures affected within the cavernous sinus, notably cranial nerves III-VI, as well as symptoms resulting from impaired venous drainage from the orbit and eye.

Classic presentations are abrupt onset of unilateral periorbital edema, headache, photophobia, and bulging of the eye (proptosis).

Other common signs and symptoms include:

Ptosis, chemosis, cranial nerve palsies (III, IV, V, VI). Sixth nerve palsy is the most common. Sensory deficits of the ophthalmic and maxillary branch of the fifth nerve are common. Periorbital sensory loss and impaired corneal reflex may be noted. Papilledema, retinal hemorrhages, and decreased visual acuity and blindness may occur from venous congestion within the retina. Fever, tachycardia and sepsis may be present. Headache with nuchal rigidity may occur. Pupil may be dilated and sluggishly reactive. Infection can spread to contralateral cavernous sinus within 24–48 hours of initial presentation.

A strain (also known colloquially as a pulled muscle or torn muscle) is an acute or chronic soft tissue injury that occurs to a muscle, tendon, or both (contractile components). The equivalent injury to a ligament is a sprain.