Musculoskeletal Imaging

What’s the Best Next Study for Chronic Ankle Pain When Tendons Are Suspect?

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What's the Best Next Study for Chronic Ankle Pain When Tendons Are Suspect?

A 48-year-old recreational runner presents to your clinic with four months of persistent pain along the inside of her right ankle, worsening after runs. The pain is localized, and you note mild swelling and tenderness to palpation just posterior to the medial malleolus. You ordered ankle radiographs a month ago, which were reported as normal. Your clinical suspicion is high for posterior tibial tendon dysfunction, but you need to confirm the diagnosis and assess its severity before referring to physical therapy or orthopedics. This article details the American College of Radiology (ACR) guided workflow for this exact scenario: chronic ankle pain with normal or nonspecific radiographs where a tendon abnormality is the primary concern. For this presentation, the ACR rates ankle ultrasound as Usually Appropriate.

Who Fits This Clinical Scenario for Chronic Ankle Pain?

This guidance applies to a specific patient population: adults or children with chronic ankle pain (typically lasting three months or longer) where initial imaging with radiographs has not revealed a clear cause. The key feature of this scenario is a focused clinical suspicion for a tendon-related problem, based on the location of pain, tenderness on examination, or specific functional deficits. This includes pain localized to the medial, lateral, or posterior ankle that corresponds to the course of a major tendon.

This workflow is not intended for:

  • Acute Ankle Injuries: Patients with recent trauma where fracture or acute ligamentous rupture is the primary concern.
  • Suspected Osteochondral Lesions: Patients with mechanical symptoms like locking or catching, where the primary suspicion is a cartilage or subchondral bone injury. This presentation follows a different ACR imaging pathway.
  • Primary Ankle Instability: Patients whose main complaint is a feeling of the ankle “giving way,” suggesting ligamentous laxity rather than tendinopathy.
  • Pain of Uncertain Etiology: Patients with diffuse, non-specific chronic ankle pain where a clear anatomical source cannot be identified on physical exam.

Correctly identifying your patient’s presentation is crucial, as these similar but distinct scenarios have different recommended imaging studies. This article focuses strictly on the workup of suspected tendinopathy after normal radiographs.

What Diagnoses Are You Working Up with Suspected Tendon Abnormality?

When initial radiographs are unrevealing, the differential diagnosis for chronic, localized ankle pain shifts to the soft tissues, particularly the tendons that stabilize and move the joint. The next imaging study is chosen to visualize these structures and differentiate among several potential pathologies.

Posterior Tibial Tendon Dysfunction (PTTD): This is a primary consideration for medial ankle pain and a common cause of adult-acquired flatfoot deformity. The posterior tibial tendon is critical for supporting the medial longitudinal arch. Imaging aims to identify tendinosis (degeneration), tenosynovitis (inflammation of the tendon sheath), or partial versus full-thickness tears.

Peroneal Tendinopathy: A frequent cause of chronic lateral ankle pain, especially in active individuals. The peroneal longus and brevis tendons can be affected by tendinosis, tenosynovitis, or longitudinal split tears. Imaging is also crucial for assessing tendon position to rule out subluxation or dislocation from the retromalleolar groove, a dynamic process that can be missed on static imaging.

Achilles Tendinopathy: This is a very common overuse injury causing posterior ankle pain. The clinical question is often to differentiate between mid-substance tendinosis (degeneration within the tendon body) and insertional tendinopathy (at its attachment to the calcaneus), which may be associated with a retrocalcaneal bursitis or Haglund deformity. Imaging helps confirm the diagnosis and assess for any partial tears.

Flexor Hallucis Longus (FHL) Tendinopathy: Often called “dancer’s tendinitis,” this is a less common but important cause of posteromedial ankle pain, particularly in athletes whose activities involve repetitive plantar flexion. Imaging can reveal tenosynovitis or tendinosis as the FHL tendon passes through its fibro-osseous tunnel.

Why Is Ultrasound the Recommended First Study for Suspected Ankle Tendinopathy?

For a patient with chronic ankle pain, normal radiographs, and suspected tendinopathy, both US ankle and MRI ankle without IV contrast are rated as Usually Appropriate by the ACR. Both are excellent, radiation-free (0 mSv) modalities for evaluating soft tissues. However, ultrasound often serves as the more practical and diagnostically powerful first choice in this specific context.

Ultrasound offers superb spatial resolution, allowing for detailed visualization of tendon fiber architecture to identify subtle tendinosis, fluid in the tendon sheath (tenosynovitis), and tears. Its primary advantage is the ability to perform a dynamic assessment. A sonographer can have the patient actively move their ankle, which is invaluable for diagnosing conditions like peroneal tendon subluxation, where the tendons displace from their groove only with certain movements. This dynamic capability is unique to ultrasound. Furthermore, ultrasound can be used to precisely guide therapeutic injections, such as a corticosteroid or anesthetic, in the same session.

Magnetic Resonance Imaging (MRI) without contrast is equally appropriate and provides a more global, panoramic view of the ankle. It is excellent for detecting bone marrow edema, assessing surrounding ligaments, and identifying occult osteochondral lesions that might mimic tendinopathy. MRI is less operator-dependent than ultrasound and can be superior for evaluating deeper structures or when the diagnosis is less certain.

So why are other advanced imaging studies rated lower?

  • MRI ankle without and with IV contrast is rated Usually not appropriate. For primary tendinopathy, gadolinium-based contrast adds little diagnostic information, as inflammation and degeneration are typically well-visualized on non-contrast sequences. Adding contrast increases cost, scan time, and introduces the risks associated with contrast agents.
  • CT ankle without IV contrast is also rated Usually not appropriate. While excellent for bone detail, CT has poor intrinsic soft-tissue contrast, making it suboptimal for evaluating tendon morphology. Given the radiographs are already normal, CT offers limited additional value for this clinical question and exposes the patient to ionizing radiation (☢ <0.1 mSv).

What’s Next After an Ankle Ultrasound? Downstream Workflow

The results of the ankle ultrasound will guide your next steps, creating a clear decision-making pathway for patient management.

If the ultrasound is positive for tendinopathy (e.g., PTTD, peroneal tendinosis): The findings confirm your clinical suspicion. The report will typically grade the severity (e.g., mild tendinosis, high-grade partial tear), which dictates the management plan. This usually involves a referral to physical therapy for conservative management, consideration of bracing, or a consultation with podiatry or orthopedic surgery for more severe cases like full-thickness tears or advanced PTTD with foot deformity.

If the ultrasound is negative or inconclusive: A negative, high-quality ultrasound makes significant tendinopathy unlikely. If the patient’s symptoms are severe and your clinical suspicion remains high, this is the point to consider the other Usually Appropriate study: MRI ankle without IV contrast. MRI can provide a more comprehensive assessment and may reveal an alternative diagnosis missed on both radiographs and ultrasound, such as an occult osteochondral lesion, stress fracture with bone marrow edema, or sinus tarsi syndrome.

If the ultrasound suggests a different pathology: The study may uncover an unexpected finding, such as a ganglion cyst, a ligamentous injury, or signs of impingement. This new diagnosis would then direct the subsequent workup and management, potentially leading to a different ACR variant workflow.

In some cases, a US-guided anesthetic injection, rated as May be appropriate, can serve as a diagnostic and therapeutic tool. If injecting a local anesthetic into the tendon sheath provides significant temporary pain relief, it strongly supports that tendon as the pain generator.

Pitfalls to Avoid (and When to Get Help)

Navigating the workup for chronic ankle pain requires attention to a few common pitfalls. First, avoid anchoring on a single diagnosis; while tendinopathy is likely, keep a broad differential. Second, ensure the imaging order is specific. When ordering an ultrasound, specify the area of maximal tenderness (e.g., “Rule out posterior tibial tendinopathy”) to guide the sonographer. Third, do not mistake a normal radiograph for a clean bill of health in a symptomatic patient; significant soft-tissue pathology is common with normal bones. Finally, recognize the limitations of a static exam; if peroneal subluxation is suspected, specifically request a dynamic ultrasound assessment.

If a patient presents with red flag symptoms such as night pain, fever, or unexplained weight loss, escalate the workup to include inflammatory markers and consider MRI to evaluate for infection or neoplasm.

Related ACR Topics and Tools

For a comprehensive overview of imaging for all chronic ankle pain presentations, from initial workup to post-operative evaluation, please see our parent guide. For other specific questions or to explore the tools used to build these workflows, the following resources are available.

Frequently Asked Questions

Why is MRI also ‘Usually Appropriate’ if ultrasound is often the first choice?

Both MRI and ultrasound are excellent for evaluating tendons. While ultrasound’s dynamic capability is a key advantage for this scenario, MRI provides a more comprehensive, global view of all ankle structures, including bone marrow, cartilage, and ligaments. It is less operator-dependent and can be the better choice if the diagnosis is uncertain or if you suspect multiple co-existing pathologies beyond just a single tendon.

Should I order an MRI with contrast if I suspect inflammation?

Generally, no. For this specific scenario, the ACR rates MRI with contrast as ‘Usually not appropriate.’ Most tendinopathies, including tendinosis and tenosynovitis, are well-visualized on non-contrast MRI sequences (like fluid-sensitive T2-weighted images). Intravenous contrast rarely adds diagnostic value for the primary question of tendon pathology and is reserved for specific indications like suspected infection (abscess) or tumor.

What if my patient’s pain is more about instability or ‘giving way’ than localized tendon pain?

If the primary symptom is instability, the patient fits a different clinical scenario: ‘Chronic ankle pain. Ankle radiographs normal or nonspecific, suspected ankle instability.’ In that case, the imaging workup is different, with MRI without contrast and MR arthrography being rated higher to specifically evaluate the ligaments (e.g., ATFL, CFL). This highlights the importance of matching the clinical presentation to the correct ACR variant.

Can ultrasound reliably distinguish between a partial and full-thickness tendon tear?

Yes, in the hands of an experienced sonographer, high-resolution ultrasound is highly accurate for differentiating between partial-thickness and full-thickness tendon tears. It can visualize fiber discontinuity and measure the size of the defect and any tendon retraction, which are critical details for guiding surgical versus non-surgical management.

Is there any role for stress radiographs in this scenario?

For this specific scenario—suspected tendinopathy—the ACR rates stress radiographs as ‘Usually not appropriate.’ Stress views are designed to assess ligamentous integrity and instability, not tendon morphology. Since the clinical question here is about the tendon itself (e.g., degeneration, inflammation, or tear), a soft-tissue imaging modality like ultrasound or MRI is the correct next step.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 26, 2026