Compartment syndrome

Pressure building inside a limb after injury or a cast, strangling the muscle from within. Pain that keeps increasing despite painkillers is the alarm.

What it is

A dangerous rise in pressure within a closed muscle compartment of a limb, cutting off its own blood supply.

It follows fractures, crush injuries, tight casts or bandages, burns, surgery, and sometimes a prolonged period lying on a limb, including after collapse or overdose.

Muscle begins to die within hours. The treatment is emergency surgery, a fasciotomy, cutting the tissue open to release the pressure. Delay causes permanent muscle death, contracture, nerve damage and sometimes amputation.

The classic teaching is the six Ps, but most of them are late and unreliable. **The useful signs are early: pain that is severe, increasing, and not relieved by strong painkillers, and pain on passively stretching the muscle.** A person in a plaster who is in escalating agony needs the plaster split and the limb assessed, not more analgesia.

Loss of pulse is a very late sign. Waiting for it is waiting too long.

A particular trap is somebody who cannot report pain: after regional anaesthesia, in a child, in someone with a learning disability or dementia, or in someone unconscious. There, rising analgesia requirements, agitation and a tense swollen limb are the signals.

Chronic exertional compartment syndrome is a different, non-urgent condition causing predictable calf pain during exercise in runners.

Signs you might notice

Pain that is severe and getting worse, out of proportion to the injury, and not controlled by strong painkillers.

Pain on passively stretching the muscles, for example pulling the toes up in a calf compartment.

A tense, swollen, hard limb.

Pins and needles or numbness.

Late and unreliable: pallor, paralysis, absent pulse, coldness. Do not wait for these.

**999 or immediate hospital assessment** for escalating pain after a fracture, cast or crush injury.

If a cast or bandage is tight and pain is rising, it must be split or removed immediately. Nobody should be told to wait until morning.

In anybody who cannot report pain, treat a tense swollen limb with rising distress as this until proven otherwise.

How it can affect day-to-day life

Most cases follow a fracture, and most delays follow reassurance that pain after a fracture is normal. It is, up to a point, and pain that keeps climbing despite treatment is not.

The instruction to elevate a limb is generally right, and in suspected compartment syndrome the limb should be kept at heart level rather than raised, because raising it further reduces blood flow. That detail is easily got wrong.

After fasciotomy the wounds are left open and closed later or grafted, which is alarming to see and needs explaining.

Long-term consequences include weakness, contracture, altered sensation and chronic pain, needing prolonged physiotherapy and occupational therapy.

For the chronic exertional form in runners, the pattern is reproducible pain at a predictable distance that resolves with rest, and it is investigated non-urgently.

Supporting someone well

Take escalating pain seriously, particularly in a plaster.

Ask for the cast to be split or removed if pain is rising. This is a reasonable request and it is reversible.

Do not raise a suspected compartment syndrome limb above the heart; keep it level.

Go to A and E rather than waiting for a fracture clinic appointment.

Say compartment syndrome; it prompts pressure measurement and a surgical review.

For anybody who cannot report pain, watch for a tense limb, rising analgesia requirements and distress.

Afterwards, ask for physiotherapy early to prevent contracture.

For predictable exercise-related calf pain, ask for assessment for chronic exertional compartment syndrome rather than repeatedly treating shin splints.

Where to get help

999 or A and E immediately for escalating pain after injury, surgery or a cast.

The orthopaedic team; the fracture clinic for urgent review of a tight cast.

Chartered Society of Physiotherapy for rehabilitation guidance afterwards.