What are the possible causes and treatments for inability to fully extend the elbow?

Inability to Fully Extend the Elbow: Differential Diagnosis and Management

The inability to fully extend the elbow requires systematic evaluation starting with radiographs to exclude fracture or dislocation, followed by stress fluoroscopy or advanced imaging based on clinical findings, with treatment ranging from conservative management for mild instability to surgical intervention for severe cases.

Primary Diagnostic Considerations

Traumatic/Acute Causes

• Occult fractures are present in 12.8% of patients with positive elbow extension test (inability to fully extend while sitting with shoulders at 90° flexion), including radial head, olecranon, and coronoid process fractures 1
• Ligamentous injuries causing instability can be graded by stress fluoroscopy: <10° joint widening indicates slight instability, >10° indicates moderate instability, and frank redislocation indicates gross instability 1, 2
• Elbow dislocation with associated ligamentous disruption commonly presents with extension deficit 1
• Osteochondral lesions of the radial head can cause extension deficits and should be considered even in young patients without prior trauma 3

Mechanical/Structural Causes

• Loose bodies or osteochondral fragments within the joint space mechanically block extension 1
• Heterotopic ossification restricts motion and is best detected on radiographs or CT rather than MRI 1
• Osteophytes in the olecranon fossa prevent full extension 3
• Hypertrophic synovial plica can cause locking and pain with extension attempts 1

Soft Tissue Causes

• Capsular fibrosis of the anterior joint compartment restricts extension 3, 4
• Posttraumatic scar tissue limits range of motion 3
• Synovitis causes pain and mechanical restriction 3

Chronic/Inflammatory Causes

• Rheumatoid arthritis is the most common rheumatic cause of elbow instability and extension loss 5
• Other erosive arthritides can produce similar presentations 5

Congenital Causes

• Synostosis, arthrogryposis, and pterygium present with fixed extension deficits from birth or early childhood 6

Diagnostic Algorithm

Initial Evaluation

• Obtain standard radiographs as the first-line imaging to exclude fracture or dislocation 1, 2
• Perform elbow extension test: patient sits with shoulders at 90° flexion and attempts full elbow extension; inability indicates high likelihood of pathology requiring further workup 1

When Radiographs Are Normal or Indeterminate

For suspected fracture:

• CT without contrast identifies occult fractures with superior sensitivity compared to radiographs, clarifying fracture morphology, fragment size, and displacement 1

For suspected ligamentous injury:

• Stress fluoroscopy evaluates joint stability under varus/valgus stress at full extension and 30° flexion, with reliable agreement to MRI findings 1
• MRI without contrast assesses ligamentous and tendon injuries when radiographs are negative but symptoms persist 2

For mechanical symptoms (locking, catching):

• MRI without contrast detects loose bodies (enhanced by joint fluid on T2-weighted sequences), osteochondral lesions, and synovial plica 1
• CT arthrography has 93% sensitivity for loose bodies and 79% accuracy overall, though small bodies may be obscured by contrast 1

For dynamic pathology (snapping, intermittent symptoms):

• Dynamic ultrasound has 96% sensitivity and 81% specificity for detecting ulnar nerve dislocation and snapping triceps syndrome, superior to static MRI 7
• CT in flexion and extension reveals dynamic pathology not visible on static imaging 7

Treatment Algorithm

Mild Instability (<10° Joint Widening)

• Conservative management with rest, activity modification, NSAIDs, and physical therapy achieves significantly better outcomes (77.6% Mayo Elbow Performance Score) 2
• Progressive rehabilitation starting at 2-6 weeks with eccentric strengthening exercises 2

Moderate Instability (>10° Joint Widening)

• Prolonged conservative management with extended protection period and careful progression of rehabilitation 2
• Consider corticosteroid injection for persistent symptoms, though this may inhibit long-term healing 7, 2
• Arthroscopic intervention if conservative therapy fails after 5-9 months 7

Severe Instability (Frank Redislocation)

• Immediate surgical consultation for fixation is required 2

Mechanical Obstruction (Loose Bodies, Osteochondral Lesions)

• Arthroscopic treatment with removal of loose bodies or microfracture of osteochondral lesions restores full range of motion 3
• Anterior capsular release for pathologically thickened capsule increases total arc of motion by average of 38° (from 59° to 97°) 4

Capsular Contracture

• Surgical anterior release when nonoperative techniques fail, with postoperative continuous passive motion superior to extension splinting alone (45° vs 26° improvement in total arc) 4

Critical Pitfalls to Avoid

• Static MRI misses dynamic pathology: Consider dynamic ultrasound or stress imaging if symptoms persist despite negative MRI 7
• Overlooking occult fractures: Use the elbow extension test to identify patients requiring CT even when radiographs appear normal 1
• Excessive corticosteroid use: While providing short-term relief, injections can reduce tendon strength and inhibit healing long-term 2
• Inadequate stress testing: Fluoroscopic stress evaluation at multiple positions (full extension, 30° flexion, pronation/supination, varus/valgus) is necessary to grade instability accurately 1
• Delayed surgical referral: Obtain consultation for refractory pain, imaging evidence of instability, erosions, or impending pathologic fracture 5