Bilateral Calf Pain in a Marathon Runner
A 34-year-old female marathon runner presents with a 3-month history of bilateral anterolateral lower-leg pain that begins 15-20 minutes into runs and forces her to stop. The pain resolves within 5-10 minutes of rest. She denies night pain, rest pain, or foot numbness. She increased weekly volume from 55 to 70 km over 4 weeks while training for a spring marathon. Examination shows normal dorsalis pedis and posterior tibial pulses, no swelling, no erythema, and mild tenderness over the anterior compartments. Pain is reproduced by active dorsiflexion against resistance after a 10-minute treadmill run but not at rest. Plain radiographs are normal. She has tried neutral shoes, calf stretching, and 6 weeks of reduced running, but symptoms returned when she resumed her previous volume. She wants to know whether she can run a half-marathon in 8 weeks.
1. What is the most likely diagnosis, and how would you frame the differential?
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The most likely diagnosis is chronic exertional compartment syndrome of the anterior compartments, bilateral. The hallmark is reproducible pain at a specific exercise intensity, relief with rest, and a normal examination at rest. The differential includes medial tibial stress syndrome, which usually has medial tibial border tenderness and may hurt at rest; tibial stress fracture, which often has focal bony tenderness, night pain, and impact pain; popliteal artery entrapment syndrome, which is more often unilateral and may cause paresthesia or diminished pulses with provocative maneuvers; lumbar radiculopathy, which usually has shooting pain and neurologic findings; and tendinopathy, which produces localized tendon pain. Bilateral symptoms and normal pulses do not exclude compartment syndrome. The recent 27% volume increase is a plausible trigger. Normal radiographs reduce but do not exclude stress fracture. Ask specifically about paresthesia, foot drop, tightness, and whether pain is cramping. Document reproducibility with exercise.
2. What diagnostic test would you use, and how should the results be interpreted?
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Diagnosis is confirmed with intramuscular compartment pressure testing, ideally before and after exercise in the symptomatic compartment. Common Pedowitz criteria are a pre-exercise pressure of at least 15 mmHg, a 1-minute post-exercise pressure of at least 30 mmHg, or a 5-minute post-exercise pressure of at least 20 mmHg; some centers use dynamic pressure monitoring. The test should reproduce the patient's symptoms with exercise and be performed by an experienced clinician. Resting MRI is often normal and should not be used alone to exclude chronic exertional compartment syndrome; exercise MRI or near-infrared spectroscopy may be adjuncts but are not universally available. If pressure testing is unavailable, a careful clinical diagnosis can be made, but the rationale should be documented. Exclude stress fracture with MRI if focal bony tenderness or high-risk features are present. The key is not to label this as shin splints and simply prescribe rest.
3. Outline the nonoperative plan, indications for surgical referral, and return-to-running criteria.
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First-line care is relative load reduction, not absolute rest. For 6-8 weeks, reduce running volume by 50-70%, avoid hills and speed work, and substitute low-impact cross-training. Address training errors, cadence, overstriding, and footwear; gait retraining may reduce anterior compartment demand. Calf and foot intrinsic strengthening, hip stabilization, and a gradual plyometric progression are useful. If symptoms persist after 3-6 months of structured nonoperative care, referral for fasciotomy is reasonable; results are good in properly selected patients. She should not run a half-marathon in 8 weeks while symptomatic. Return-to-run criteria include pain-free easy running for 30 minutes, no tightness, and a weekly volume increase of no more than about 10%. After surgery, return is typically 6-12 weeks with graded rehabilitation. Document the shared decision and the risk of continuing to train through symptoms.