Chronic Exertional Compartment Syndrome

Chronic exertional compartment syndrome (CECS) is exercise-induced pain and tightness in a leg compartment, caused by a reversible rise in pressure within it, that settles within minutes of stopping.

It mainly affects young, active adults, especially runners and military personnel, and the anterior compartment is the one most often involved. The pattern is reproducible: symptoms start at a predictable time or distance, build with continued activity and ease with rest.

CECS is one cause of exercise-induced leg pain, alongside medial tibial stress syndrome (MTSS), stress fracture, popliteal artery entrapment syndrome (PAES) and nerve entrapment. It is a different condition from acute compartment syndrome, which is a surgical emergency.

The lower leg has 4 osseofascial compartments, each bounded by fascia, bone and the interosseous membrane. The non-compliant fascia is central to the condition.

The compartments, and the symptoms when each is affected:

• •Anterior: tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius; deep peroneal nerve. Most often affected: first web space numbness and dorsiflexion weakness during symptoms
• •Lateral: peroneus longus and brevis; superficial peroneal nerve. Dorsal foot numbness and eversion weakness
• •Deep posterior: tibialis posterior, flexor hallucis longus, flexor digitorum longus; tibial nerve. Medial plantar numbness and plantarflexion weakness. Tibialis posterior often sits in its own fascial sub-compartment
• •Superficial posterior: gastrocnemius, soleus, plantaris. Least often affected in isolation

The traditional explanation is that muscle swells with exercise and the fascia cannot expand, so pressure rises, compromising perfusion and compressing nerves until exercise stops. That mechanism remains unproven.

Risk factors include endurance running, military training, muscle hypertrophy, anabolic steroid use and previous compartment surgery.