Could ankle pain in a patient over 65 with a normal ankle X‑ray and only a mild anterior effusion on ultrasound be referred from another site?

Referred Pain in Elderly Ankle Pain with Normal Imaging

Yes, ankle pain in a patient over 65 with normal radiographs and only mild effusion on ultrasound should prompt evaluation for referred pain from the hip or lumbar spine, as these are well-recognized sources of lower extremity pain that can masquerade as ankle pathology. 1

Primary Sources of Referred Pain to Consider

Hip Pathology as a Referred Pain Source

• Hip disorders frequently refer pain to the knee and lower leg, and in patients with unremarkable ankle imaging, hip radiographs should be obtained when clinical suspicion exists. 1
• The pattern of referred pain from hip pathology typically follows dermatomal and sclerotomal distributions, potentially manifesting as ankle discomfort in elderly patients with degenerative hip disease. 1
• In your patient over 65 with normal ankle X-rays, obtain AP pelvis and lateral hip radiographs to exclude occult hip osteoarthritis, avascular necrosis, or insufficiency fractures that commonly present with atypical lower extremity pain. 1

Lumbar Spine Pathology as a Referred Pain Source

• Radiculopathy from lumbar spine disease must be considered when ankle radiographs are unremarkable, particularly if the patient reports any back symptoms, radicular features, or neurologic complaints. 1
• L5 and S1 nerve root compression can produce ankle and foot pain that mimics primary ankle pathology, especially in elderly patients with multilevel degenerative disease. 1
• Obtain lumbar spine radiographs (AP and lateral views) if there is clinical evidence or concern for spinal pathology—look specifically for neurologic deficits, dermatomal sensory changes, or pain that worsens with spinal loading. 1

Clinical Red Flags That Suggest Referred Pain

Features Favoring Hip Origin

• Pain that is worse with hip internal rotation, flexion, or weight-bearing through the hip joint rather than isolated ankle motion. 1
• Groin discomfort or anterior thigh pain accompanying the ankle symptoms. 1
• Limited hip range of motion on examination, particularly internal rotation in flexion. 1

Features Favoring Lumbar Spine Origin

• Radicular pain distribution following L5 (dorsum of foot, great toe) or S1 (lateral foot, heel) dermatomes. 1
• Positive straight leg raise test or reproduction of ankle pain with lumbar spine maneuvers. 1
• Sensory deficits, reflex asymmetry (ankle jerk for S1), or motor weakness (foot dorsiflexion for L5, plantarflexion for S1). 1
• Pain that improves with sitting or spinal flexion (suggesting spinal stenosis) or worsens with extension. 1

Why Mild Ankle Effusion Does Not Exclude Referred Pain

• The presence of a mild anterior ankle effusion on ultrasound does not establish a primary ankle disorder as the pain source, because effusions can be incidental, age-related, or secondary to altered gait mechanics from proximal pathology. 2, 3
• Research demonstrates that ankle effusions do not correlate with injury severity—in one study of 100 acute ankle injuries, 42% had effusions but the presence of effusion did not relate to the severity of underlying pathology. 3
• In elderly patients, chronic low-grade synovitis and small effusions are common incidental findings that may not explain acute or persistent pain. 4

Algorithmic Approach to This Clinical Scenario

1. Perform a focused hip examination: assess hip range of motion (especially internal rotation), palpate for groin tenderness, and perform log-roll and FABER tests. 1

2. Perform a focused lumbar spine and neurologic examination: check straight leg raise, assess L5/S1 dermatomes and myotomes, test ankle and patellar reflexes, and observe gait for antalgic or Trendelenburg patterns. 1

3. If hip examination is abnormal or clinical suspicion exists, obtain AP pelvis and lateral hip radiographs to evaluate for osteoarthritis, avascular necrosis, or insufficiency fractures. 1

4. If lumbar spine examination is abnormal or radicular features are present, obtain lumbar spine radiographs (AP and lateral) and consider MRI of the lumbar spine if neurologic deficits are documented. 1

5. If both hip and spine examinations are unremarkable and ankle pain persists beyond 1–3 weeks despite appropriate functional treatment (bracing, supervised exercise therapy), obtain MRI of the ankle without contrast to evaluate for occult fractures, osteochondral lesions, or ligamentous injuries that may have been missed on initial imaging. 5, 6

Common Pitfalls to Avoid

• Assuming that mild ultrasound findings (such as a small effusion) fully explain the patient's symptoms—in elderly patients, incidental degenerative changes and effusions are prevalent and may be unrelated to the presenting complaint. 4, 3
• Failing to examine the hip and lumbar spine in an elderly patient with "ankle pain"—referred pain is a frequent cause of diagnostic error in lower extremity complaints, and guidelines explicitly recommend hip and spine imaging when ankle radiographs are normal. 1
• Ordering advanced ankle imaging (MRI) prematurely without first excluding referred pain sources—this wastes resources and delays diagnosis of the true pathology. 1, 5
• Overlooking vascular claudication or peripheral neuropathy—elderly patients may describe claudication or neuropathic pain as "ankle pain," and these conditions require entirely different management. 7