Disc Injury

Disc injury is as misunderstood as it is common.    

The key to understanding why your disc injury is not healing may lie in this insight: 

There are no less than eight major mechanisms of injury that may arise from a single disc bulge.  

A disc injury can cause back pain or it can cause leg pain. A disc injury can cause brief pain or it can cause constant pain. A disc injury can improve with [fill-in-the-black] treatment or it may worsen with [fill-in-the-black] treatment.  

The injury mechanism, rather than the anatomical diagnosis, determines the range of symptoms as well as the appropriate treatment.  

WHAT ARE EIGHT MECHANISMS OF DISC INJURY?  

1. A centralized disc bulge pressing on a spinal nerve.  
2. A off-center disc bulge pressing on the nerve root within the neural foramen.  
3. An injury to the cartilage endplate, the most vulnerable part of your disc.  
4. An unstable joint that may cause a variable symptom profile and sharp catches with bending or rolling over in bed.  
5. A compression-intolerant disc that cannot tolerate gravity and forces you to lie down throughout the day.  
6. An problem with the nerves ability to flow—impaired neurodynamics—which make it hard to sit in your recliner, walk briskly, or look down at your iPhone. 
7. Spinal canal stenosis from the disc (and perhaps other factors) blocking out the nerves in your spinal canal and causing sciatica in both legs. As if sciatica in one leg was not bad enough!  
8. The most dangerous mechanical disc injury is cauda equina syndrome. In this condition, the lumbar and sacral spinal nerves are compressed. This might lead to incontinence, urine retention, and sexual dysfunction.  

WHY SHOULD I CARE ABOUT MY DISC’S INJURY MECHANISM ANYWAY? 

The main reason you should care is because the best treatment for your disc injury depends upon this detailed understanding. The injury mechanisms will determine your: 

• Range of symptoms — back pain or leg pain 
• Frequency of symptoms — a brief “zinger” or a painful crisis 
• Response to treatment — improvement or worsening with McKenzie-based therapy/traction/epidural steroid injection/discectomy/fusion 

 The reason most disc care fails is the diagnosis was never subcategorized into a functional category that would account for: 

• Safe postures, motions, and loads 
• Pain-triggers: aggravating postures, motions, and loads 
• Deficiencies in overall physical conditioning 
• The prognosis and natural history of the condition  
• The optimal range, type, and progression of rehabilitation exercises.  

ISN’T MY DOCTOR AND THERAPIST DIAGNOSING MY MECHANISM ALREADY?    

In my experiences in standard pain medicine—in the first two years of my career—the focus and treatment algorithm is based on the spinal imaging and on the symptoms—not on the root-cause of your injury mechanisms.    

Here’s how the process typically works in practice.    

1. Pain Presentation — “Hey doc I pulled my back lifting the couch.” The family doctor prescribes a “safe” pain medication.
   •  Tylenol
   • NSAID’s
   • Muscle Relaxers
2. Spinal Imaging — “Hey doc my back still hurts, can I get an MRI or something?” With persistent pain, spinal imaging will be ordered…at some point.  

Many doctors will order an x-ray immediately but many won’t order an MRI at first—due, perhaps, to decrees from the bean-counting higher-ups. Citing the fact that most back pain resolves on its on anyway in three months, I know of health systems that won’t let you get an MRI until you’ve been in agony for three months.  

So finally, you have an MRI. It shows that you have a central disc bulge at L5-S1 with surrounding Modic changes on the surrounding vertebral bodies.    

Mystery solved, right?  

1. Symptom-focused treatment — After the MRI, you still have pain. You might then receive: 
   • Physical therapy  
   • More pain medication  
   • Stronger pain medication, perhaps even opioids  
   • Spinal injections 
   • And surgery.  
2. Patient-blaming (optional) —If it’s been too long, your doctor might start blaming you for your pain. He might say things such as:  

• “It’s all in your head.”  
• “mind over matter”  
• “it’s stress/depression/anxiety”  
• “Have you ever heard of John Sarno?”  
• If you’re a woman: “it may be hormones”  
• And my favorite: “You should have healed by now.”  

As you can see from the example above, patients feel stuck and misunderstood because the key features of the disc-injury have not been described to them and they have not received an appropriate functional diagnosis  that has defined their pain triggers, disc-injury subtype, and individualized treatment program.  

CAN AN MRI TELL ME WHICH MECHANISMS I HAVE?   

In part. 

An MRI will show a centralized disc bulge, neural foraminal stenosis, (some) endplate injuries, and spinal canal stenosis.  

The MRI will not, however, indicate whether the visual abnormality is the cause of your pain.  

 Nor will the MRI describe the biomechanical features of your disc injury.    

It will also not usually detect key mechanisms such as instability, compression-intolerance, or nerve impaired dynamics.    

The most important information can be reliably and consistently determined only through  a skilled clinical assessment.    

BUT WAIT, AREN’T DISC BULGES PAIN-FREE?  

Some disc bulges can be pain-free.    

No question.    

This fact is proven by multiple studies featuring pain-free back subjects who, on imaging, are found to have disc bulges.    

The most cited of these studies, from 1994, was published in the New England Journal of Medicine. In this study, the authors wrote that “the discovery by MRI of bulges or protrusions in people with low back pain may frequently be coincidental.”    

This statement has been widely and wildly misinterpreted in the following ways: 

• All disc bulges are pain-free. No: some disc bulges are pain-free. Some ≠ all.  
• Disc pain is imagined. There’s clinicians who actually make careers out of telling patients that disc and other spine injury is psychological in origin. Employers, insurance carriers, and defense attorneys love those gaslighting clinicians. Hey if the pain is all your in head, don’t blame us for making you lift that 200-pound box.  
• Unless there is sciatica, the disc is not the source of pain. Depending on the mechanism, disc pain can cause back or sciatic leg pain.    

HOW COME SOME DISC BULGES ARE PAIN-FREE AND MINE HURTS?    

The disc is comprised of three parts:  

• The annulus fibers  
• The nucleus gel 
• And a thin cartilage cap on the top and bottom of each disc.    

Here is the key fact to understand why much disc damage can take place, including those that produce disc bulges, without symptoms arising:    

The annulus fibers and nucleus gel, which comprise over 95% of the disc by volume, do not have sensory fibers.    

A disc bulge involving annulus and nucleus damage won’t produce pain at first. Even as the annulus fibers delaminate and fray, there is no sensory nerves within this part of the disc to signal pain.    

However, with the progression of a disc bulge, tissues that do have sensory nerve endings will become damaged. Think of the spinal nerves and their roots that, upon mechanical compression by a disc bulge, causes sciatica leg pain.    

With damage to the disc, the dictum that annulus fibers lack sensory nerve endings no longer holds true. Disc damage reduces the pressure within the disc. This loss of pressure allows the ingrowth of nearby nerve endings—a process known as peripheral sprouting.    

With this new hardware to detect pain, the annulus may become a source of discogenic pain.    

In general, disc damage will not become painful until one of the eight mechanisms of disc pain emerges.    

Prior to the mechanism arising, you may have been sustaining silent damage for years.    

ISN’T IT TRUE THAT A DISC INJURY IS A CAREER-ENDER ONCE YOU HAVE IT? 

Most mechanisms of disc injury can respond to treatment, once the injury is thoroughly defined. The problem with most care is patients receive a treatment program that is inappropriate for their particular problem. Flawed programming may be:  

• Replicating pain-triggers and therefore making the problem worse 
• Overly demanding and beyond the capacity of the spine, therefore aggravating the present injury—or creating new injury.  
• Not correctly addressing deficiencies in posture, movement, and exercises.   

With the correct care, the standard disc patient who has already failed other treatment has a probable chance of recovery without surgery. Of patients told they need surgery, many—but not all!—can successfully manage their condition through spine hygiene and rehab exercise.    

Select References   

McGill, Stuart. Low back disorders: evidence-based prevention and rehabilitation. Human Kinetics, 2015. 

McGill, Stuart M., and Jacek Cholewicki. “Biomechanical basis for stability: an explanation to enhance clinical utility.” Journal of Orthopaedic & Sports Physical Therapy 31.2 (2001): 96-100.   

Adams, Michael A., Manos Stefanakis, and Patricia Dolan. “Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain.” Clinical biomechanics 25.10 (2010): 961-971.   

Divi, Srikanth N., et al. “Does the size or location of lumbar disc herniation predict the need for operative treatment?.” Global Spine Journal 12.2 (2022): 237-243.   

Genevay, Stephane, and Steven J. Atlas. “Lumbar spinal stenosis.” Best practice & research Clinical rheumatology 24.2 (2010): 253-265.   

Gitelman, Alex, et al. “Cauda equina syndrome: a comprehensive review.” Am J Orthop (Belle Mead NJ) 37.11 (2008): 556-62.