Articular Surfaces
- Ulnar notch of the radius (concave): A shallow concavity on the medial surface of the distal radius. The radius pivots around the ulnar head at this surface.
- Ulnar head (convex): The rounded head of the distal ulna articulates with the ulnar notch. The ulnar head also has an inferior articular surface that contacts the triangular fibrocartilage complex (TFCC).
- Triangular fibrocartilage complex (TFCC): A fibrocartilaginous disc that separates the distal ulna from the carpal bones (primarily the lunate and triquetrum). The TFCC attaches from the ulnar border of the distal radius to the ulnar styloid and fovea. It is the primary stabilizer of the DRUJ, cushions ulnocarpal loading, and allows smooth rotation. TFCC tears are a common cause of ulnar-sided wrist pain.
Movements and ROM
At the DRUJ, the radius rotates around the ulna. The ulna remains essentially stationary while the distal radius sweeps from lateral (in supination) to medial (in pronation), carrying the hand with it.
Capsular Pattern
Equal limitation of pronation and supination
Same as the proximal radioulnar joint. Both forearm rotation movements are equally restricted in capsular pathology.
Resting Position
- 10° supination
- Maximum capsular laxity
Close-Packed Position
- 5° supination (full forearm supination)
- TFCC and capsule maximally taut
End-Feels
| Movement |
Normal End-Feel |
Type |
| Pronation |
Capsular (firm) |
TFCC, dorsal capsule, interosseous membrane, supinator stretch |
| Supination |
Capsular (firm) |
TFCC, palmar capsule, interosseous membrane, pronator stretch |
Ligaments
Triangular Fibrocartilage Complex (TFCC)
- Attachments: Ulnar border of the distal radial articular surface → ulnar styloid process and fovea at the base of the ulnar styloid. Includes the articular disc, meniscus homologue, dorsal and palmar radioulnar ligaments, ulnocarpal ligaments, and extensor carpi ulnaris subsheath.
- Function: The primary stabilizer of the DRUJ. Transmits approximately 20% of axial load from the wrist to the forearm (the radiocarpal joint transmits ~80%). Acts as a cushion between the ulnar head and the proximal carpal row. The dorsal and palmar radioulnar ligaments within the TFCC provide the primary restraints against dorsal and palmar translation of the ulna.
- Injury mechanism: Fall on an outstretched hand with forearm rotation (pronation or supination at impact). Repetitive loading in ulnar deviation and rotation (gymnasts, racquet sports). Degenerative tears increase with age — the TFCC thins with positive ulnar variance (ulna longer than radius).
- Assessment test: TFCC compression test (ulnar deviation + axial compression + forearm rotation — pain at ulnar wrist). Fovea sign (deep palpation at the fovea between the ulnar styloid, FCU tendon, and pisiform — point tenderness indicates deep TFCC tear). Piano key test (press the distal ulna palmarly — excessive motion or pain indicates DRUJ instability).
- Condition link: TFCC tear, DRUJ instability, ulnar impaction syndrome
Dorsal and Palmar Radioulnar Ligaments
- Attachments: Dorsal and palmar margins of the ulnar notch of the radius → ulnar head and ulnar styloid
- Function: The dorsal radioulnar ligament resists palmar translation of the ulna in pronation. The palmar radioulnar ligament resists dorsal translation of the ulna in supination. Together they are the primary checkreins against translation at the DRUJ.
Mobilization Techniques
Hands-on instruction is required. The descriptions below provide clinical reference detail for understanding and supervised practice. They are not a substitute for instructor-led technique training. Correct hand placement, force dosage, and tissue response interpretation require hands-on coaching and feedback.
Convex-Concave Rule at the DRUJ
The convex ulnar head sits in the concave ulnar notch of the radius. During mobilization, we typically glide the
radius on the fixed ulna (concave on convex), so the glide is in the
same direction as the restricted movement. Alternatively, if gliding the ulna on the fixed radius (convex on concave), the glide is
opposite to the restriction.
General Contraindications
- Absolute: DRUJ instability, acute TFCC tear with instability, distal radius or ulna fracture, active infection
- Relative: TFCC tear (stable — Grade I–II only), post-surgical (follow surgeon timeline), osteoporosis
Dorsal-Palmar Ulnar Glide
Purpose: Restores pronation (dorsal ulnar glide) or supination (palmar ulnar glide). This technique mobilizes the ulna on the fixed radius.
Patient position:
- Seated with the forearm pronated and resting on the table (for dorsal glide) or supinated (for palmar glide)
- Elbow flexed to 90°
Hand placement:
- Stabilizing hand: Grips the distal radius firmly, stabilizing it against the table
- Mobilizing hand: Thumb and index finger grip the distal ulna (ulnar head). For dorsal glide: force directed dorsally (posteriorly). For palmar glide: force directed palmarly (anteriorly).
Technique execution:
- Dorsal ulnar glide (restores pronation): Apply an oscillatory force pushing the ulnar head dorsally. The convex ulna moves on the concave radial notch — convex on concave — glide is opposite to the restricted pronation direction, which means dorsal glide facilitates pronation.
- Palmar ulnar glide (restores supination): Apply an oscillatory force pushing the ulnar head palmarly.
- Grade I–II: Gentle oscillations for assessment and pain modulation
- Grade III: Oscillations into end-range resistance — stretching the dorsal or palmar radioulnar ligaments
- Duration: 20–30 seconds per set, 2–3 sets
Indications:
- Decreased dorsal or palmar DRUJ glide on accessory motion testing (compare bilaterally)
- Pronation or supination limitation with capsular end-feel
- Post-Colles' fracture or post-immobilization stiffness
Technique notes:
- Common error: Gripping too proximally on the ulnar shaft — this does not isolate DRUJ motion.
- Critical: If the piano key test is positive (excessive dorsopalmar ulnar translation), the DRUJ is unstable — do not mobilize. Refer for TFCC assessment.
- Reassessment: Re-test pronation and supination PROM.
Distal Radioulnar Distraction
Purpose: General capsular stretch and pain modulation at the DRUJ. Separates the articular surfaces, decompresses the TFCC.
Patient position:
- Seated, forearm in neutral on the table
Hand placement:
- One hand grips the distal radius, the other grips the distal ulna. Apply opposing forces — pull the radius laterally and the ulna medially, separating the two bones at the DRUJ.
Technique execution:
- Gentle oscillatory or sustained distraction separating the distal radius and ulna
- Grade I–II: Pain modulation and assessment
- Grade III: Sustained distraction for capsular stretch
- Duration: 20–30 seconds per set, 2–3 sets
Indications:
- General DRUJ stiffness with capsular end-feel on pronation/supination
- Post-fracture compression of the DRUJ (Colles' fracture commonly disrupts DRUJ alignment)
Muscles Crossing This Joint
- anatomy/muscles/pronator-quadratus — the primary pronator at the DRUJ; a deep, flat muscle spanning the distal quarter of the forearm between the radius and ulna
- anatomy/muscles/extensor-carpi-ulnaris — runs through a groove on the dorsal ulnar head; its subsheath is part of the TFCC complex and helps stabilize the DRUJ
Conditions Affecting This Joint
- TFCC tear — traumatic or degenerative; the most common cause of ulnar-sided wrist pain; presents with pain on forearm rotation, ulnar deviation, and grip
- DRUJ instability — TFCC and radioulnar ligament disruption; positive piano key test; often follows distal radius fracture
- Ulnar impaction syndrome — positive ulnar variance (ulna longer than radius) causes repetitive impaction of the ulnar head against the TFCC and proximal carpal row; chronic ulnar wrist pain worsened by ulnar deviation and grip
- Distal radius fracture (Colles' fracture) — commonly disrupts DRUJ alignment and TFCC; post-fracture DRUJ stiffness is extremely common
Clinical Notes
- Post-Colles' fracture DRUJ stiffness is the rule, not the exception. Distal radius fractures frequently disrupt the DRUJ and TFCC. After cast removal, forearm rotation is almost always limited. Early DRUJ mobilization (when medically cleared) is essential to prevent permanent pronation/supination loss.
- Ulnar-sided wrist pain differential. The DRUJ and TFCC are the most common sources. Differentiate from ECU tendinopathy (pain with resisted ulnar deviation + extension), pisotriquetral arthritis (pisiform grind test), and ulnar nerve compression at Guyon's canal (sensory changes in ring/little finger). The fovea sign and TFCC compression test help localize DRUJ/TFCC pathology.
- DRUJ instability must be ruled out before mobilizing. The piano key test (pressing the ulnar head palmarly and assessing for excessive dorsopalmar translation and pain) is the primary screening test. If instability is present, mobilization is contraindicated.
Key Takeaways
- The TFCC is the primary DRUJ stabilizer and transmits ~20% of axial wrist load — its integrity must be assessed (piano key test, fovea sign) before mobilizing.
- The proximal and distal radioulnar joints are mechanically obligated — restriction at either joint limits forearm rotation.
- Post-Colles' fracture DRUJ stiffness is extremely common — early mobilization when cleared prevents permanent pronation/supination loss.
