Forearm Pain That Doesn’t Quite Match the Injury? Hmm
Acute forearm compartment syndrome is a surgical emergency in which pressure inside a closed muscle compartment rises high enough to cut off its own blood supply.
The muscle begins to die within hours.
The single most reliable sign is pain that is far worse than the injury should produce, and that escalates rather than settles despite elevation and strong painkillers.
If that is happening right now, stop reading and go to an emergency department.
Why the forearm
The forearm muscles sit in compartments wrapped in fascia — tough, fibrous, and essentially inelastic.
Bleeding or swelling inside that wrapping has nowhere to go, so pressure climbs. Once it exceeds the pressure in the small vessels, blood stops reaching the muscle.
Muscle tolerates this for roughly 4 to 6 hours.
Nerve tolerates it for less.
Common causes:
- forearm and elbow fractures, especially supracondylar fractures in children;
- crush injuries;
- a cast or bandage applied too tight;
- restored blood flow after a period of arterial blockage;
- high-pressure injection injuries; and
- anticoagulated patients with relatively minor trauma.
The signs, in the order they appear
- Pain out of proportion. Earliest and most important. Deep, relentless, escalating
- Pain on passive stretch. Straightening the fingers when the flexor compartment is involved produces severe pain. This is the most sensitive clinical test
- A tense, wooden-feeling forearm — not soft, not squashy
- Paresthesia. Numbness and tingling as nerves lose their supply
- Paralysis. Lack of ability to move the muscles, wrists and fingers.
- Pulselessness. Very late, and often never — a present pulse does NOT rule this out
Waiting for a lost pulse before acting is waiting for the limb to be already lost. Pressure that kills muscle is lower than the pressure needed to stop an artery.
In children, and in anyone who can’t report reliably, the signs are the three A’s: increasing Analgesia requirement, Anxiety, and Agitation. These often precede everything else.
What to do while getting there
- Split or remove every cast, bandage and dressing down to the skin
- Keep the limb at HEART LEVEL — not elevated. Raising it above the heart lowers the pressure driving blood in and makes the perfusion worse
- Nothing to eat or drink; surgery may be immediate
- Do not ice it. Cold reduces perfusion further
Diagnosis is clinical. Compartment pressure measurement is used where the picture is unclear or the patient is unconscious, but a convincing clinical picture is enough to operate on.
Treatment
Emergency fasciotomy — the fascia is opened along the length of the compartment to release the pressure.
- Wounds are left open initially and closed days later, sometimes with a skin graft
- Done within about 6 hours, muscle and nerve usually recover fully
- Beyond 12 hours, permanent damage is the expectation rather than the risk
Volkmann’s ischaemic contracture is what untreated compartment syndrome leaves behind: dead muscle replaced by scar, which shortens and pulls the wrist and fingers into a fixed claw. Reconstruction is possible — tendon lengthening, muscle transfers — but it is salvage, and hands do not come back to normal.
Chronic exertional compartment syndrome is different
The chronic version — forearm pump in climbers, motocross riders and rowers — is a separate condition with a separate article: forearm pain and arm pump.
It is exercise-induced, resolves with rest, and is elective. The acute version described here does not resolve and is not elective.
The window
- 0 to 6 hours: fasciotomy, full recovery expected
- 6 to 12 hours: partial damage likely
- Beyond 12 hours: permanent muscle loss and contracture
Nearly every window on this site is measured in weeks. This is the one measured in hours, and it is the shortest one you will read here.
Related reading
- Forearm Pain and Arm Pump: When the Timing Is the Diagnosis
- Forearm Fracture Recovery: Why Rotation Is the Number That Matters
- CRPS in the Hand: Warning Signs and Why Speed Matters
- Nerve Repair Recovery: Why It Takes a Year, and How to Track It
Every article on this site is written using the Closing Window Method: name the window your condition runs on, find where you are in it, and act while it’s still open.