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What is a Disc Protrusion?

Disc protrusions are highly frequent, especially with the advancement of age. One of the most frequent back pain reasons is a disc protrusion. The vertebral column is constituted by 33 vertebrae.

“The vertebral column, synonymous with spinal column or spine, and known colloquially as the backbone, forms the central axis of the body’s skeleton. Superiorly, it articulates with the skull, and inferiorly, it articulates with the two hip bones which in turn give attachment to the lower limbs. The vertebral column comprises the following five regions in cephalocaudal sequence: cervical, thoracic, lumbar, sacral and coccygeal. The vertebral column contains the spinal cord within the vertebral canal and thereby protects the spinal cord from external trauma. Degenerative diseases of the vertebral column account for the vast majority of spinal disorders in clinical practice. Trauma, neoplastic disease and developmental anomalies account for most of the remainder of spinal problems. Optimal medical and surgical management of spinal disease are crucially dependent on accurate clinical and radiological diagnosis and these, in turn, are reliant on a sound understanding of the structural and functional anatomy of the vertebral column.”1

For simplicity’s sake, we could say that each of the vertebrae is constituted by:

  • A round-like vertebral body, which is the anterior portion of the vertebrae.
  • Spinous processes, which are bony structures that project outwards from the posterior part of each vertebra.

Between these two structures is the spinal cord, which runs from top to bottom. The spinal cord gives rise to the spinal nerves, which go through the limbs and trunk. However, the movement of the spine is conditioned by structures that allow the sliding of one vertebra over another. These structures are:

Facet joints

They are the contact points of the upper vertebrae and the vertebra immediately below it. “Lumbar facet joints (FJs) constitute a common source of pain and remain a misunderstood, misdiagnosed and improperly treated pathology. Facet osteoarthritis is the most frequent form of facet pathology. Although imaging for back pain syndrome is very common (radiographs, MRI, CT, SPECT), there is no effective correlation between clinical symptoms and degenerative spinal changes, with some imaging findings that may, in specific cases, appear irrelevant to the clinical setting. Clinical facet joint syndrome is defined as a unilateral or bilateral back pain radiating to one or both buttocks, sides of the groin, and thighs, and stopping above the knee. However, in some cases, patients’ symptoms in the setting of low back pain may lack specificity, as facet joints may mimic the pain caused by herniated discs or compressed roots.”2

Longitudinal ligaments

These ligaments add stability to the spine and keep its shape as a whole.

Intervertebral discs

They are cartilaginous structures located between one vertebra and another. Their function is to avoid friction and help buffer movements and added pressure, acting as a cushion and a stabilizing factor. “The intervertebral discs lie between the vertebral bodies, linking them together. The components of the disc are nucleus pulposus, annulus fibrosus and cartilaginous end-plates. The blood supply to the disc is only to the cartilaginous end-plates. The nerve supply is basically through the sinovertebral nerve. Biochemically, the important constituents of the disc are collagen fibers, elastin fibers and aggrecan. As the disc ages, degeneration occurs, osmotic pressure is lost in the nucleus, dehydration occurs, and the disc loses its height. During these changes, nociceptive nuclear material tracks and leaks through the outer rim of the annulus. This is the main source of discogenic pain. While this is occurring, the degenerative disc, having lost its height, effects the structures close by, such as ligamentum flavum, facet joints, and the shape of the neural foramina. This is the main cause of spinal stenosis and radicular pain due to the disc degeneration in the aged populations.”3

They are made of two parts:

  • Nucleus pulposus: it has a gelatinous consistency and is designed to absorb compression forces. “Intervertebral discs have a soft deformable central region, the nucleus pulposus, which is composed mostly of a proteoglycan gel held together loosely by a sparse network of type-II collagen fibrils. These fibrils have diameters in the region of 30–500 nm, and do not clump together to form gross fibers. However, they interact physically at certain nodal points to hold the tissue together, and anchor it to adjacent tissues. Proteoglycans are very large molecules with sugar subunits, which have a strong electrostatic attraction to water. Consequently, nucleus tissue swells greatly in water unless constrained by surrounding tissue and by applied mechanical loading. Loading causes the water content of the nucleus, which is approximately 80 % in a young adult, to vary diurnally by 20 %, being highest during night-time rest, and lowest following daytime activity”4
  • Fibrous rings: are made of collagen. It surrounds the nucleus pulposus and limits rotation. “The annulus fibrosus of the intervertebral disc is a complex, radial-ply connective tissue consisting of concentric lamellae of oriented collagen. Whilst much is known of the structure of the mature annulus, less is known of how its complex collagenous architecture becomes established; an understanding of which could inform future repair/ regenerative strategies.”5

“Low back pain is a common problem affecting the general population. In 5% of patients these symptoms are due to lumbar disc protrusions. Low back pain with sciatica is much more frequently associated with a disc prolapse than low back pain alone. Motor and sensory deficits are present in 50–90% of patients with a herniated lumbar disc. When bladder symptoms or progressive motor weakness are present, surgery is carried out as an emergency. In the absence of these symptoms 75–90% of patients with acute sciatica due to a protruded lumbar disc experience resolution of symptoms without surgery.”6

A vertebral protrusion occurs when the fibrous annulus bulges out of its natural space between two vertebrae, causing pressure on nerve roots that are projecting out.

“Extensive pressure within the nucleus pulposus is higher in individuals between 30 and 50 years of age than in the elderly. The conclusion is that posterior displacement of the disc will be more likely to appear when increased intradiscal pressure coincides with some damage to the posterior annular fibers. In other words, the combination of intradiscal pressure and lowered resistance of the annulus fibrosus is the main biomechanical factor contributing to protrusion–prolapse. When the expansive forces of the nucleus pulposus decrease and, because of the loss of water, the disc gradually deflates, the tendency to displacement diminishes. Other factors protecting the ageing disc against displacements are increasing stiffness of the posterior ligaments, which limit spinal mobility, and the formation of osteophytes, which distribute the load over a larger area.”7

There is a natural protective mechanism that prevents this type of injury which are the back’s muscles. When the back makes an effort, the muscles contract in coordination, allowing them to distribute and stabilize the load.

There are several circumstances that can directly generate a protrusion. The most frequent is erosion of the vertebrae. Thus, over the years, the vertebral disc loses strength and elasticity and ends up yielding to physical forces. It can also happen due to acute overload, for example, when bending over, carrying too much weight and getting up abruptly. Finally, vertebral protrusion can occur by a single powerful hit to the back, however, this is really rare.

In addition, there are some circumstances that predispose the individual to suffer a protrusion. They are, old age, obesity, lack of physical activity and weak back muscles. It also predisposes the person when spending a lot of time sitting, especially leaning forward, as the vertebral disk goes backwards in this position. Vibrations such as driving a tractor and certain genetic predispositions are also considered risk factors.

Many times, the severity of the protrusion is mild enough to not compress the nerves. In these cases, it may not cause pain or discomfort, but when it generates symptoms, there is usually pain in the back, the neck and in the lumbar area, depending on where the protrusion is located.

“Low back pain (LBP) is a major health problem that has an enormous effect on many people especially on those who are sitting for prolonged periods. The patients with LBP usually alter their motion patterns to compensate for limited functional motion through different strategies. This alternation may cause local or global musculoskeletal overload which is believed to play a causative role in exacerbating the back disorders or pain.”8

“LBP symptoms can derive from many potential anatomic sources, such as nerve roots, muscle, fascial structures, bones, joints, intervertebral discs (IVDs), and organs within the abdominal cavity. Moreover, symptoms can also spawn from aberrant neurological pain processing causing neuropathic LBP. The diagnostic evaluation of patients with LBP can be very challenging and requires complex clinical decision-making. Nevertheless, the identification of the source of the pain is of fundamental importance in determining the therapeutic approach. Furthermore, during the clinical evaluation, a clinician has to consider that LBP can also be influenced by psychological factors, such as stress, depression, and/or anxiety. History should also include substance use exposure, detailed health history, work, habits, and psychosocial factors. Clinical information is the leading element that drives the initial impression, while magnetic resonance imaging (MRI) should be considered only in the presence of clinical elements that are not definitely clear or in the presence of neurological deficits or other medical conditions.”9

This pain can radiate to the arms if the origin is cervical or to the leg if the origin is lumbar. This is because the nerves that innervate the extremities originate from the spinal cord.

“Lumbar disc protrusion is common. Its pathogenesis is unclear but is known to include endogenous factors (hereditary, developmental and degenerative) and exogenous factors (stress, nutrition, strain, trauma and so on). The term ‘lumbar disc protrusion’ describes the morphology and its classification is usually based on the position and morphology of protrusion on radiographic images. However, the morphology of the protrusion often does not correlate with clinical symptoms, which are more closely related to the various pathological changes. Therefore, the types of pathological change should be considered in the classification of lumbar disc protrusion.”10

“Lumbar disc herniation is a common condition that frequently affects the spine in young and middle-aged patients. The lumbar intervertebral disc is a complex structure composed of collagen, proteoglycans, and sparse fibrochondrocytic cells that serve to dissipate forces exerted on the spine. As part of the normal aging process, the disc fibrochondrocytes can undergo senescence, and proteoglycan production diminishes. This leads to a loss of hydration and disc collapse, which increases strain on the fibers of the annulus fibrosus surrounding the disc. Tears and fissures in the annulus can result, facilitating a herniation of disc material, should sufficient forces be placed on the disc. Alternatively, a large biomechanical force placed on a healthy, normal disc may lead to extrusion of disc material in the setting of catastrophic failure of the annular fibers.

Regardless of etiology, herniations represent protrusions of disc material beyond the confines of the annular lining and into the spinal canal. Back pain may occur due to disc protrusions that do not enter the canal or compromise nerve roots. The more treatable condition of lumbar radiculopathy, however, arises when extruded disc material contacts, or exerts pressure, on the thecal sac or lumbar nerve roots. The pain associated with lumbar radiculopathy occurs due to a combination of nerve root ischemia and inflammation resulting from local pressure and neurochemical inflammatory factors present within the disc material.

Incidence: Lumbar disc herniations exist on a continuum of degenerative spinal processes that include intervertebral disc degeneration and lumbar spondylosis. Many studies have demonstrated that lumbar herniations, protrusions, and annular tears are present in asymptomatic individuals and, in certain instances, can represent normal aging of the intervertebral disc.”11

Classically, it was considered that the vertebral protrusion should always be treated with surgical intervention. However, it is now known that a more conservative approach should be tried. This consists of postural hygiene, meaning, adopting correct or proper postures. It is also recommended to perform some types of exercise that promote supporting the back and abdominal musculature. You can also visit a specialist so they can provide you with the most efficient and recommended exercises.



(1) Mahadevan, V. (2018). Anatomy of the vertebral column. Surgery (Oxford). Available online at

(2) Perolat, R., Kastler, A., Nicot, B., Pellat, J. M., Tahon, F., Attye, A., … & Krainik, A. (2018). Facet joint syndrome: from diagnosis to interventional management. Insights into imaging, 9(5), 773. Available online at

(3) Raj, P. P. (2008). Intervertebral disc: anatomy-physiology-pathophysiology-treatment. Pain Practice, 8(1), 18-44. Available online at

(4) Adams, M. A. (2015). Intervertebral disc tissues. In Mechanical properties of aging soft tissues (pp. 7-35). Springer, Cham. Availablee online at

(5) Hayes, A. J., Isaacs, M. D., Hughes, C., Caterson, B., & Ralphs, J. R. (2011). Collagen fibrillogenesis in the development of the annulus fibrosus of the intervertebral disc. Eur cell mater, 22, 226-241. Available online at

(6) Ushewokunze, S., Abbas, N., Dardis, R., & Killeen, I. (2008). Spontaneously disappearing lumbar disc protrusion. Br J Gen Pract, 58(554), 646-647. Available online at

(7) Ombregt, L. (2013). Ageing of the lumbar spine. A System of Orthopaedic Medicine (Third Edition).  

(8) Kuai, S., Liu, W., Ji, R., & Zhou, W. (2017). The Effect of Lumbar Disc Herniation on Spine Loading Characteristics during Trunk Flexion and Two Types of Picking Up Activities. Journal of healthcare engineering, 2017. Available online at

(9) Allegri, M., Montella, S., Salici, F., Valente, A., Marchesini, M., Compagnone, C., … & Fanelli, G. (2016). Mechanisms of low back pain: A guide for diagnosis and therapy. F1000Research, 5. Available online at

(10) Ma, X. L. (2015). A new pathological classification of lumbar disc protrusion and its clinical significance. Orthopaedic surgery, 7(1), 1-12. Available online at

(11) Schoenfeld, A. J., & Weiner, B. K. (2010). Treatment of lumbar disc herniation: evidence-based practice. International journal of general medicine, 3, 209. Available online at


Robert Velasquez
13 October, 2018

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Hello everyone, my name is Robert Velazquez. I am a content marketer currently focused on the medical supply industry. I studied Medicine for 5 years. I have interacted with many patients and learned a more:

599 thoughts on “What is a Disc Protrusion?

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