Osteochondrosis: Diagnosis of the Muscular System

Back muscles are not "passengers" but active stabilizers of spinal segments. In chronic pain, a decrease in cross-sectional area, fatty infiltration, and decreased "quality" of the multifidus and erector spinae muscles are often detected; these changes correlate with the duration of symptoms and functional limitations. Modern reviews emphasize the consistent association of chronic low back pain with atrophy/fatty infiltration of the paravertebral muscles. [1]

The "two-way" effect is also important: disc degeneration alters the biomechanics and load on muscles, while weakness/fatigue increases micromovements and worsens degeneration. Therefore, a proper diagnosis of osteochondrosis includes not only the discs and facets, but also the condition of the muscles—using clinical tests, imaging, and (selectively) instrumental methods. [2]

Another reason to examine muscles is prognosis and treatment decisions. Fatty infiltration and severe atrophy respond less well to standard rehabilitation and are associated with slower recovery after spinal surgery; muscle "sarcopenia" is also found in healthy individuals with age, which is important to consider when interpreting images. [3]

Finally, muscles are a measurable "target." Unlike many passive structures, strength endurance and coordination can be objectively measured and trained. This makes muscle assessment useful even during the first consultation: it helps prioritize treatment plans and set realistic goals. [4]

Table 1. What exactly do we evaluate in the muscular system when we experience back pain?

Component	Why is it important?	What do we measure?
Strength and endurance of the extensors/flexors/lateral stabilizers	Associated with the ability to "hold" segments	Sorensen test, McGill test set, dynamic tests. [5]
Coordination of deep stabilizers	Important for "anti-slip" movements	Craniocervical flexion test (CCFT), cervical/lumbar neurodynamic tests. [6]
Muscle structure and composition	Prognosis, goal of rehabilitation	MRI/CT (area, fat), ultrasound elastography. [7]
Neuromuscular activation	Pain subtypes, risk of chronicity	(Caution) surface EMG (sEMG) according to strict protocol. [8]

Clinical "strength" and "endurance" tests: what do they really show?

The most commonly used tests in clinical practice are the Sorensen test (isometric back extensor endurance) and the McGill test (extensors, flexors, and lateral stabilizers). A 2024 review confirms the high reproducibility of these tests, and studies on modifications demonstrate good comparability and the usefulness of the extensor/flexor/lateral ratios. These tests are appropriate for use in most patients without significant neurological deficits. [9]

The Sorensen test is standardized, simple, and sensitive to extensor endurance deficits; it is actively studied even in multiple repetitions to assess fatigue. In chronic pain, the average hold duration is typically lower than in healthy individuals, but interpretation should take into account age, body weight, and training status. [10]

For the cervical spine, the cervical flexor endurance test and the craniocervical flexion test (CCFT) are used. Systematic reviews indicate that the CCFT distinguishes well between healthy individuals and patients with nonspecific neck pain and is valid specifically as an assessment of deep flexor activation (using electromyography), but is less well-related to pain severity and is not very sensitive to short-term changes. In other words, it measures "the quality of activation" rather than "pain scores." [11]

Overall, the reliability of key cervical tests (flexor/extensor endurance, CCFT, hand dynamometry) is acceptable when properly standardized. This allows them to be safely included in the initial assessment and dynamic monitoring, but conclusions should be based on a combination of indicators, not a single test. [12]

Table 2. Quick reference for "basic" tests

Zone	Test	What does it show?	What to rely on in interpretation
Small of the back	Sorensen	Extensor endurance	Compare ratios with flexor/lateral tests.[13]
Small of the back	McGill's set	Balance of endurance on three planes	Norms depend on gender/age. [14]
Neck	CCFT	Deep flexor coordination	Good for "differential diagnosis", not for "pain assessment". [15]
Neck	Flexor/extensor endurance test	Strength endurance	Acceptable reliability in standardization. [16]

Muscle imaging: MRI/CT as a "microscope" of muscle quality

MRI allows for the assessment of the cross-sectional area and fatty infiltration of the multifidus and spinal erector muscles; quantitative approaches (including Dixon sequences) and semi-quantitative scales distinguish well between patients with and without chronic pain. The influence of age should be kept in mind: fatty infiltration increases even in healthy individuals—the phenomenon of "back sarcopenia." [17]

The "less muscle, more pain" relationship isn't always linear: geometry, symmetry, and the combination with disc/facet changes are all important. Review studies note that "quality" (fat, edema, fibrosis) better reflects dysfunction than pure cross-sectional area. This may influence the prognosis of interventions and the choice of rehabilitation focus. [18]

After spinal surgery, paravertebral muscle atrophy is a common finding and a potential factor in outcome; therefore, surveillance protocols increasingly include targeted muscle assessment on follow-up imaging. Muscle-sparing interventions (minimally invasive approaches) are associated with better preservation of muscle mass. [19]

CT is inferior to MRI in assessing the "quality" of soft tissues, but it clearly shows shape, calcifications, and bony landmarks. Density measurements (HU) are also used in studies as a surrogate for "fatness." In routine practice for "osteochondrosis," this is usually sufficient if MRI is unavailable or contraindicated. [20]

Table 3. What is useful to include in the conclusion of muscle visualization

Parameter	Why is this important?	Note
Area and symmetry of multi-partite/rectifiers	Stability, functional reserve	Specify levels (e.g. L4-S1). [21]
Fatty infiltration	Prognosis, muscle "quality"	Qualitative/semi-quantitative assessment. [22]
Associated disc/facet changes	Explains the mechanical conflict	Write holistically, not in isolation. [23]
Postoperative changes	Risks of weakness/pain	Record the dynamics on control MRI/CT. [24]

Instrumental methods "beyond the clinic": when they are appropriate

Surface EMG (sEMG). The technology is widely available, but diagnostic accuracy and reliability vary from "weak" to "good" depending on the task and protocol. A recent review emphasizes that sEMG is more useful for investigating activation patterns and biofeedback than for diagnosis; it should be used as a supplement, not a "pain detector." Classic meta-analyses also showed group differences but not accuracy for individual diagnosis. [25]

Ultrasound elastography (shear waves). New studies show differences in the stiffness of the erector spinae, multifidus, and even the thoracolumbar fascia in people with chronic pain compared to healthy individuals. Elastography holds promise for "objectifying" muscle sensitivity/rigidity and monitoring interventions (massage, exercise, vibration therapy), but threshold standards are still being developed. [26]

Risk profiling based on EMG fatigue. Studies have shown that EMG fatigue patterns in the extensors can predict the risk of future pain episodes. This is scientifically interesting, but it is too early for widespread screening: protocols vary, and transferability to real-world practice is limited. [27]

Local palpation and trigger points. This is an important part of the examination, but as a standalone diagnostic test, palpation is unreliable and should be confirmed by functional tests or instrumental assessments (if necessary). In questionable cases, elastography can help digitize local tenderness. [28]

Table 4. Instrumental methods and their place

Method	What does it give?	Limitations/comments
sEMG	Activation patterns, biofeedback	Wide range of accuracy; not a "diagnostician." [29]
SWE elastography	Quantitative muscle/fascia stiffness	No universal thresholds; useful dynamically. [30]
EMG fatigue	Risk profile, research tasks	There is no standard for routine screening.[31]
Palpation	Topography of pain	Low reliability as a "single test".[32]

How to assemble the "muscle" part of the initial assessment: step by step

The first step is history and observation: pain duration, episodes of "breakdowns," activity level, fear of movement. Assess posture and stereotypes: "cautious" gait, shoulder girdle asymmetry, unloading positions (for example, with cervical radiculopathy). These details will help select tests. [33]

The second step is basic endurance tests (Sorensen, McGill) and neck tests (flexor/extensor endurance, CCFT). Compare not absolute seconds, but the relationships between muscle groups and their correspondence to complaints. If neurological symptoms or "red flags" are evident, strength tests are postponed and visualization is used instead. [34]

The third step is targeted palpation and provocation: costovertebral joints, paravertebral columns, and muscle-tendon junctions. Reproducibility of "recognizable" pain is more important than "diffuse tenderness." If in doubt, targeted MRI with muscle assessment and/or elastography (if available) should be performed. [35]

Step four: Use tools as indicated: sEMG as a training/biofeedback tool, elastography for the "myofascial" phenotype. Record the results as a baseline: this will simplify evaluation of therapy effectiveness and discussions with the patient. [36]

Table 5. Mini-algorithm for “muscle” assessment of back pain

Step	Target	Tools
1. History + observation	Identify limitations/fears/patterns	Questionnaire, gait/posture observation. [37]
2. Basic samples	Quantify endurance	Sorensen, McGill; Cervical endurance tests. [38]
3. Palpation/provocations	Localize the source	Local tests + comparison with complaints. [39]
4. PRN Tools	Clarify phenotype/monitoring	sEMG (learning), SWE (stiffness). [40]

Connecting Muscles to Discs and Nerves: Clinical-Radiological Integration

Chronic pain rarely involves only the discs or only the muscles; more often, it's a "combination." A classic example is lateral stenosis: posterolateral protrusion + facet hypertrophy + hypertonicity and fatigue of the local muscle corset. The MRI report should explicitly identify muscle findings and their possible contribution to the symptoms. [41]

Fatty infiltration of the multifidus and erector spinae muscles is associated with worse functional outcomes and more pronounced postural instability; however, it is age-dependent, and fat itself does not equal the source of pain. Integration helps here: symptom level ↔ stenosis/protrusion level ↔ local muscle weakness. [42]

In the neck, CCFT and endurance tests help identify deep flexor deficits, which often coexist with facet-disc changes and tension-type headaches. It is appropriate to use CCFT as a "coordination gauge" rather than a "pain thermometer." This reduces the risk of overinterpretation of the results. [43]

In the postoperative back, a meaningful muscle assessment helps differentiate "mechanical" causes of symptoms (e.g., pseudoarthrosis, segmental malalignment) from "muscle deconditioning." In the former case, the emphasis is on surgery/injection methods, while in the latter, targeted rehabilitation and endurance training are essential. [44]

Table 6. “Coupling” of discs, joints and muscles: typical scenarios

Scenario	What to look for	Diagnostic progress
Lateral stenosis with radiculopathy	Protrusion + facets + straighteners	MRI/CT + endurance tests; target extensors/laterals. [45]
Non-specific neck pain	Deep flexor deficiency (CCFT)	CCFT + cervical endurance tests; coordination emphasis. [46]
Postoperative pain	Paravertebral atrophy, imbalance	Control MRI/CT with muscle description; rehabilitation plan. [47]
"Myofascial" phenotype	Localized stiffness/pain	SWE elastography for monitoring. [48]

What to record in the chart and how to explain it to the patient

Record baseline data: seconds held in tests, simple strength indicators (if a dynamometer is available), and "weak links" by zone. This helps set specific goals and track progress; the patient better understands what exactly we are "training." [49]

Rely on ratios, not just absolutes. Balance is essential for the spine: overloading the extensors while "falling" the flexors, or, conversely, weak lateral stabilizers, is a common finding. It is ratios that determine the direction of rehabilitation and explain relapses. [50]

Explain that structural findings (fat in the muscles, "bad-looking" discs) are not a death sentence: even with advanced degeneration, trained endurance and coordination reduce pain and improve function. Identify "red flags" that indicate an early return (increasing weakness, sensory/pelvic disturbances, etc.). [51]

If you use sEMG or elastography, explain their role as training/monitoring aids, not as "true cause of pain detectors." This will avoid false expectations and maintain confidence in the rehabilitation process. [52]

Table 7. Short checklist for the inspection protocol

Block	The minimum worth writing down	For what
Endurance tests	Sorensen + McGill (seconds)	Base for goals and dynamics. [53]
Cervical coordination	CCFT (pressure level, quality of technology)	Identify deep flexor deficiency. [54]
Palpation/provocations	Local zones, pain reproducibility	Link to complaints. [55]
Visualization (if done)	Muscle area/fat, symmetry, associated changes	Integrate with the clinic. [56]
Instruments (as indicated)	sEMG/Elastography: Protocol and Key Figures	Monitoring interventions. [57]

Brief conclusions

1. In case of “osteochondrosis”, muscles are an equal part of the diagnosis: evaluate strength/endurance, coordination of deep stabilizers and “quality” of muscles using MRI/elastography, but always in a clinical context. [58]
2. The Sorensen and McGill tests, cervical endurance tests, and CCFT have acceptable reliability and help guide rehabilitation; interpret results in terms of ratios rather than raw numbers. [59]
3. MRI reliably detects fatty infiltration/atrophy of the paravertebral muscles and helps with prognosis, but age and general activity are important modifiers; "fat" does not always mean "source of pain." [60]
4. sEMG and ultrasound elastography are useful adjuncts for phenotyping and monitoring, but do not replace clinical assessment and are not the “gold standard” for pain diagnosis.[61]