Radial Head Pronation
Pronation carries radial head POSTERIOR (FOOSH with pronation = posterior radial head)
Radial Head Supination
Supination carries radial head ANTERIOR (fall backward onto supinated hand)
Inversion Ankle Sprain
Talus inverts → distal fibula glides anterior → fibular head glides POSTERIOR
Carrying Angle Rule
Increased carrying angle = Cubitus Valgus → ulnar abduction → wrist adduction
Radial Head Somatic Dysfunctions
The radial head articulates with the capitulum of the humerus and radial notch of the ulna. It moves synchronously with forearm pronation and supination:
| Dysfunction | Freedom of Motion | Restriction | Mechanism of Injury (FOOSH) |
|---|---|---|---|
| Posterior Radial Head | Pronation (moves freely posterior) | Supination (resists moving anterior) | Fall on outstretched hand (FOOSH) with forearm PRONATED |
| Anterior Radial Head | Supination (moves freely anterior) | Pronation (resists moving posterior) | Fall backward onto hand with forearm SUPINATED |
Fibular Head & Ankle Sprain Biomechanics
The fibula functions as a reciprocal strut between the knee and ankle mortise:
Inversion Ankle Sprain (Most Common)
Inversion, plantarflexion, and internal rotation damage the anterior talofibular ligament (ATFL). The talus tilts medially, forcing the lateral malleolus anteriorly and the proximal fibular head POSTERIORLY.
Peroneal (Fibular) Nerve Entrapment
The common fibular nerve courses directly around the neck of the fibula just distal to the fibular head. A posterior fibular head somatic dysfunction can stretch or compress the nerve, causing foot drop (weak dorsiflexion) and numbness on the dorsum of the foot.
Eversion Ankle Sprain
Eversion damages the deltoid ligament. Forces distal fibula posterior and proximal fibular head ANTERIORLY.
Carrying Angle & Forearm Reciprocal Mechanics
The carrying angle is formed by the intersection of the longitudinal axes of the humerus and ulna (normal: 10–15° in females, 5° in males):
| Angle Abnormality | Elbow Kinematics | Ulnar Motion | Wrist Motion |
|---|---|---|---|
| Cubitus Valgus (> 15°) | Forearm deviates laterally | Ulnar Abduction | Wrist Adduction (compensatory) |
| Cubitus Varus (< 5°) | Forearm deviates medially (gunstock) | Ulnar Adduction | Wrist Abduction (compensatory) |
COMLEX / OMM Integration
NBOME High-Yield Correlate
Lower Extremity Ligament Injury Sequence in Inversion Sprains
- 1st Ligament Injured: Anterior Talofibular Ligament (ATFL) — 'Always Tears First'.
- 2nd Ligament Injured: Calcaneofibular Ligament (CFL).
- 3rd Ligament Injured: Posterior Talofibular Ligament (PTFL) — occurs only in severe trimalleolar injuries.
- 2nd Ligament Injured: Calcaneofibular Ligament (CFL).
- 3rd Ligament Injured: Posterior Talofibular Ligament (PTFL) — occurs only in severe trimalleolar injuries.
Board Traps & Common Distractors
- Trap: Confusing the distal lateral malleolus motion with proximal fibular head motion. They ALWAYS move in opposite directions! When distal fibula moves anterior, proximal fibular head moves POSTERIOR.
- Common Peroneal Nerve: If a board question describes an ankle sprain followed by inability to walk on heels or trip-and-fall gait, immediately suspect common fibular nerve injury at the fibular head.