Pain at Lateral Humerus Just Distal to the Deltoid
The most likely source of pain at the lateral humerus just distal to the deltoid insertion is radial nerve pathology, as this anatomical location corresponds precisely to where the radial nerve courses in direct contact with the posterior and lateral humerus. 1
Anatomical Basis
The radial nerve is the primary structure at risk in this specific location based on consistent anatomical relationships:
The radial nerve contacts the posterior humerus for approximately 6.3 cm, centered at the distal aspect of the deltoid tuberosity (which is 17.1 cm proximal to the lateral epicondyle). 1
The nerve lies directly against the periosteum without a protective bony groove, making it vulnerable to compression, traction, or direct injury. 1
After passing the deltoid insertion area, the nerve transitions anteriorly along the lateral humerus between the lateral intermuscular septum and bone, where it has minimal mobility and remains at risk until protected by the brachialis muscle more distally. 1
Clinical Differential Considerations
Primary Concern: Radial Nerve Injury
Radial nerve lesions are the most common nerve injury associated with humeral shaft pathology in this region, particularly with fractures or external trauma. 2
The inferior lateral cutaneous nerve of the arm (a superficial branch of the radial nerve) emerges at a mean of 14.2 cm proximal to the lateral epicondyle, which is in the region just distal to the deltoid. 3
Secondary Consideration: Lateral Epicondylitis (Less Likely)
While lateral epicondylitis is common, it typically presents with pain at the lateral epicondyle itself rather than the proximal lateral humerus:
Lateral epicondylitis occurs 7-10 times more frequently than medial epicondylitis and affects the dominant arm in 75% of cases, but the pain localizes to the lateral epicondyle, not proximal to it. 4
The posterior cutaneous nerve of the forearm branches consistently innervate the lateral epicondyle region, but this is more distal than the area described in your question. 5
Diagnostic Approach
Initial evaluation should focus on identifying radial nerve dysfunction through motor and sensory examination:
Test wrist extension, finger extension (especially at the metacarpophalangeal joints), and thumb extension/abduction. 2
Assess sensation over the dorsal first web space (superficial radial nerve distribution). 3
If clinical examination suggests tendon or ligament pathology with normal radiographs, MRI without IV contrast or ultrasound is usually appropriate as the next imaging study. 4, 6
Common Pitfalls
Do not assume lateral arm pain is always lateral epicondylitis—the anatomical location matters significantly, and pain proximal to the epicondyle suggests radial nerve involvement rather than tendinopathy. 5, 1
Radial nerve injury can occur without fracture through compression, traction, or iatrogenic causes during procedures in this region. 7
The deltoid tuberosity serves as a reliable landmark for the radial nerve location and should be identified when evaluating this region. 1