Overview – What is the Posterior Forearm?

The posterior forearm is home to the extensor compartment — the muscle group responsible for wrist extension, finger extension, grip stability, and coordinated thumb movement. Whether you’re lifting, typing, climbing, throwing, or just flexing in the mirror, the posterior forearm is working harder than you think.

This region includes 11 primary muscles (12 if including Anconeus) organized into two layers:

Superficial Layer:

Brachioradialis
Extensor Carpi Radialis Longus
Extensor Carpi Radialis Brevis
Extensor Digitorum
Extensor Digiti Minimi
Extensor Carpi Ulnaris

Deep Layer:

Supinator
Abductor Pollicis Longus
Extensor Pollicis Brevis
Extensor Pollicis Longus
Extensor Indicis

The Treadwell, DPT Mnemonic (Superficial → Deep // Lateral → Medial)

🥋 “Begin Really Rehabbing Daily, Demonstrating Urgency — Soon All Problems Pale Inevitably.”

This mnemonic is not just a memory tool — it’s a mindset:

Begin Really Rehabbing Daily, Demonstrating Urgency — Soon All Problems Pale Inevitably.

That’s anatomy, that’s consistency, that’s rehab.

Innervation – Radial Nerve & Radial Tunnel

Every posterior forearm extensor is powered by the Radial Nerve or one of its branches. This makes the region crucial for understanding:

Wrist Drop
Radial Tunnel Syndrome
Faulty grip mechanics
Proximal vs distal entrapment
Motor & sensation deficits

The radial nerve wraps from the posterior arm into the forearm — and any entrapment along that pathway can affect extension strength, grip control, and thumb stability.

Clinical Relevance – Tendinopathy & Tennis Elbow

The common extensor origin at the lateral epicondyle is a high-stress region, especially for:

Repetitive gripping
Wrist extension under load
High-demand tasks (lifting, tools, racquet sports, calisthenics)

This is where lateral epicondylitis (tennis elbow) develops — most commonly involving ECRB, but often affecting multiple extensors.

Key rehab concepts:

Progressive loading (eccentric + isometric)
Grip mechanics
Shoulder / scapular control
Tendon capacity > tendon rest
Counterforce straps for short-term relief

Tendons respond best to load, not rest —controlled progressive loading is the foundation of recovery.

Why This Matters for PTs, Students, and Lifters

✔️ Memorize all extensor muscles in order
✔️ Understand why grip strength & wrist control matter
✔️ Connect anatomy → pathology → rehab
✔️ Train and treat the forearm like a functional chain, not a single muscle

Whether you’re prepping for an exam, treating elbow pain, or just looking to build stronger, healthier forearms — master this region and everything downstream just works better.

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Posterior Forearm: Extensor Compartment Anatomy, Radial Nerve, & Mnemonic – Treadwell, DPT

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