What is the lateral recess in the lumbar spine, and what is the most common cause of its encroachment?

The lateral recess is a part of the lumbar spine where nerve roots travel after exiting the thecal sac and before entering the neuroforamen. The most common cause of lateral recess encroachment is hypertrophy of the superior articular facet. Key diagnostic features include narrowing of the lateral recess on MRI or CT, often accompanied by symptoms of radiculopathy. Clinical pearls include recognizing that lateral recess stenosis can mimic other conditions like peripheral neuropathy. A common pitfall is overlooking subtle hypertrophy on imaging, which can lead to misdiagnosis.