Degenerative Disc Disease by Emily Catford July 2021
Degenerative disc disease (DDD) is where the intervertebral discs wear down and cause pain. Degeneration can be caused by…
Age where the discs that have high water content start to dry out and thin
Through tears in the disc from activity
Through an injury.
Intervertebral discs have a very small blood supply so regeneration of the disc material is minimal after injury so they tend to continue to deteriorate over time. DDD causes an increase in chondrocytes in the annulus fibrosus that surrounds the nucleus pulposus. Over time this can cause the nucleus pulposus to change into fibrocartilage. The nucleus material can also leak into damaged areas in the outer annulus and cause herniation. This can cause the disc to shrink and bone spurs to develop (22).
Symptoms
Typical Symptoms include
Mild to disabling pain
Normally affects the cervical and lumbar vertebrae
Pain can radiate down the arms or the buttocks/legs
The pain can worsen after sitting for a while or bending/lifting/twisting.
The pain can come and go
There may be nerve root damage which can cause leg weakness and/or foot drop.
Diagnosis is made via imaging (xray, MRI, CT).
Treatment is usually physical therapy, self care, NSAIDs, pain relief, corticosteroid injections and in some cases surgery (artificial disc replacement or spinal infusions).
Self care such as maintaining a good weight, not smoking, exercises, heat and cold therapy and also modifying any triggering exercises can help (1).
The Impact of Degenerative Disc Disease (DDD)
Musculoskeletal Effects of DDD
The Effects on Spinal Curvature & Pelvic Balance
Although the cause of the pain relates to the condition of the discs, compensatory issues are likely to occur and can contribute to a cycle of pain. Intervertebral discs are primarily shock absorbers, helping to transmit loads through the spine. They also help protect the nerves (2).
Degeneration of the disc can lead to changes in the natural curves of the spine. The natural ‘S’ shape of the spine is designed to allow some ‘spring’ and shock absorption. The curvature also offsets gravity by aiding weight distribution during dynamic movement. The natural curves also help take some pressure off of the intervertebral discs (3). Spinal curvature is formed through our developmental years. Any issues that occur during this time may result in a curvature which is outside of the norm leading to compensatory issues. Any increased pressure from this can lead to DDD (3). During assessment, we need to look for any postural changes or abnormalities such as pelvic tilt and any exaggerated or flattened spinal curves.
Myofascia
Skeletal muscle is supported by myofascial tissue. Injury or stress can cause the myofascia to dehydrate and harden, locking the soft tissues into strain and dysfunction. This can alter posture and compress nervous tissue and blood and lymphatic vessels. When myofascia health is disrupted, its electrical potential is reduced causing it to dehydrate. The ground substance that usually facilitates movement becomes heavier and makes movement between the tissues harder. Fascial restrictions tend to spread through the entire system. Without treatment this will lead to muscle and postural imbalances and also compensatory injuries elsewhere in the fascial system (4).
Trigger Points
Trigger points are hyperirritable spots located in a taut band of muscle. They can produce pain locally and also in a referred pattern. Trauma or chronic repetitive trauma can cause stress to the muscle fibers and trigger points can form. They are usually present in chronic musculoskeletal disorders. Pain can be persistent, regional and decrease range of motion (ROM) at the affected joint. To palpate, trigger points feel like a harder than usual point that will elicit pain directly over the affected area and/or can also cause pain to radiate into a reference zone. A local twitch response may also be seen (5).
Muscle Imbalances
A chronic issue such as DDD, is likely to cause muscle imbalance which will need to be corrected and maintained. Repetitive loading and movements will continually stress areas and cause micro tears in the muscles. Secondary to this, other muscles can become tense around the tears to protect the area from further harm. Collagen is laid down to repair the area but repetitive trauma will keep producing tension causing hypertrophy and an altered posture (6). Overactive or tight muscles not only hinder the agonistic muscle but can become active in movements that they are not normally associated with (7). Tight muscles will pull a joint into a dysfunctional position and a weak muscle will allow it (8). If muscle imbalances are not addressed then the more stress is placed upon the body from being forced into a compensatory position. Now a cycle of pain and deterioration takes place as the tight muscles become tighter and the weak muscles become weaker. Postural changes can then take place as the joints are forced into a dysfunctional position (8).
The Impact on the Core Muscles
Lower back injury or dysfunction can cause atrophy in the multifidus muscle due to prolonged neurological dysfunction (9). The multifidus is a key stabiliser of the spine along with the transversus abdominis (TVA) and the pelvic floor muscles. The multifidus links with the thoracolumbar fascia and the TVA to provide “a natural, deep muscle corset to protect the back from injury” (10). Trigger points can also occur in the muscle which can decrease the contraction efficiency of the TVA due to decreased reciprocal inhibition. The TVA has been shown in research that it is a key stabiliser when the appendicular skeleton moves as the muscle has been shown to fire before any shoulder or leg movements in people without back pain (10).
The Impact on the Postural and Phasic Muscles
Postural muscles are involved in maintaining posture, they tend to be slow twitch and when stressed become tight and short. Phasic muscles tend to be more involved with movement and predominantly fast twitch. Postural muscles are more dominant than phasic muscles so they tend to inhibit the phasic muscle causing it to weaken and lengthen (8).
Some common key muscle relationships that we need to check for dysfunction with lower back pain are;
Latissimus Dorsi and the Thoracolumbar Fascia; The latissimus dorsi inserts into the lower 6 thoracic vertebrae, the lumbar vertebrae, the sacrum and also the supraspinatus and interspinous ligaments via the thoracolumbar fascia. The thoracolumbar fascia is a connection point between the muscles of the lower back, pelvis and legs. Its function is to create stability when muscles contract (11).
Gluteus Maximus (Gmax); The Gmax works with the hamstrings during the gait cycle. Weakness affects the posterior oblique sling (latissimus dorsi and thoracolumbar fascia) and the sacroiliac joint. Weakness also increases the activation of the hamstrings making them more dominant. Inhibition of the Gmax can lead to compensation where the latissimus dorsi may become hypertonic altering posture. Also the Gmax has a relationship with the psoas, an inhibited Gmax may cause overactive or hypertonic psoas while a hypertonic Gmax may lead to an inhibited/inactive psoas (8).
Hamstrings; The bicep femoris can become overactive which can cause increased lumbar lordosis from altering the balance of the pelvis (11).
Gluteus Medius (Gmed); The Gmed works with the Gmax during the gait cycle helping to control the position of the hip by allowing external rotation so the hip, knee and lower leg can align during walking and running. The Gmed also stabilises the pelvis during gait. Weakness in the Gmed either causes a dipping of the pelvis to either the contralateral leg (Trendelenburg sign) or the whole trunk can be shifted to the weaker side (compensatory Trendelenburg sign). Weakness in the Gmed can cause overactivity in the adductors, the piriformis and also the iliotibial band via the tensor fascia latae. This weakness can also affect the contralateral quadratus lumborum which is involved in preventing the pelvis from dropping. A strong Gmax and Gmed aids a stable knee so weakness in these areas can contribute to knee issues (8).
Quadriceps; The rectus femoris can become hypertonic causing anterior tilt and therefore lower back pain from the forced lordotic position (11).
If muscle imbalances are not corrected then the body compensates by altering its posture increasing the stress upon the musculoskeletal system and the body enters a pain spasm cycle (8).
Pain Spasm Cycle
Poor posture and muscle tension will cause ischemia and pain. When muscles are in spasm, the increased level of contraction will slow blood flow forcing them into anaerobic respiration which produces lactic acid and other waste products causing pain. A pain spasm cycle (figure 1) will start if the muscle is not released (8).
Figure 1. The Pain Spasm Cycle
Nerve Root Compression
When the discs degenerate they can lose some height, compressing the nerves. This may cause radiculopathy. Any signs of nerve compression such as nerve pain, pins and needles or numbness would be a red flag and would require referral (2).
Biopsychosocial Model & Degenerative Disc Disease
The biopsychosocial model looks at the connection of the biological, psychological and social factors surrounding a disease. As therapists we are used to treating the physical symptoms but an underlying knowledge of how the complaint/disease can affect the individual in other ways is just as important (12).
As degenerative disc disease is degenerative and chronic in nature; pain, general health and muscle imbalances need to be considered and maintained.
When designing a treatment plan, the above needs to be taken into account as stressors from one factor can influence the other factors. Knowledge of the condition and support need to be part of the treatment plan and goal setting. An awareness of looking out for any stressors that may influence the outcome of treatment is also important e.g. completely withdraws from exercise as they believe it is detrimental to them.
Figure 2. - The Biopsychosocial Model of DDD
In conclusion, to create an effective treatment plan, we need to;
Evaluate any postural abnormalities or changes
Check for muscle imbalances.
Consider outside influences as shown in the biopsychosocial model that may influence any progress.
Watch out for any red flag signs such as nerve compression/damage.
Control the disease progression.
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