Can low back strain cause enthesopathy?

Low Back Strain and Enthesopathy: Relationship and Clinical Implications

Low back strain does not directly cause enthesopathy, as these are distinct clinical entities with different pathophysiological mechanisms. 1

Understanding Enthesopathy

Enthesopathy refers to a disease process occurring at entheses, which are the attachment sites of tendons, ligaments, joint capsules, and fascia to bone 2. These conditions can be:

• Inflammatory (enthesitis)
• Degenerative
• Metabolic
• Endocrine
• Traumatic 2, 3

Entheses are sites of stress concentration where soft tissues connect to bone, making them vulnerable to overuse injuries 4. They have specialized mechanisms to withstand biomechanical forces through continuous repair processes mediated by mechanosensitive tenocytes 5.

Low Back Pain Classification and Pathophysiology

According to clinical practice guidelines, low back pain is typically classified into three broad categories:

1. Nonspecific low back pain (85% of cases)
2. Back pain potentially associated with radiculopathy or spinal stenosis
3. Back pain potentially associated with another specific spinal cause 1

Low back strain falls under the category of nonspecific low back pain, which is defined as "pain occurring primarily in the back with no signs of a serious underlying condition, spinal stenosis or radiculopathy, or another specific spinal cause" 1.

Why Low Back Strain Does Not Directly Cause Enthesopathy

Several key factors distinguish these conditions:

• Different Pathophysiology: Low back strain primarily involves muscle or ligament injury, while enthesopathy specifically affects the insertion sites of tendons and ligaments to bone 1, 2

• Mechanical Factors: Enthesopathies develop when repetitive forces cause "material fatigue" or trauma exceeds the entheses' repair capacity 5, which is different from the acute or chronic muscle strain mechanism

• Anatomical Considerations: The diagnostic classification of low back pain in clinical practice guidelines does not include enthesopathy as a direct consequence of strain 1

Conditions Where Enthesopathy May Be Present

Enthesopathy is more commonly associated with:

• Seronegative spondyloarthropathies (where it is a defining feature) 3
• Calcium deposition diseases 6
• Occupational overuse 3
• Metabolic and endocrine conditions 6
• Sports-related overuse injuries (e.g., tennis elbow, golfer's elbow, jumper's knee) 4

Clinical Implications

When evaluating patients with low back pain:

• Focus on proper diagnostic categorization using a focused history and physical examination 1
• Consider enthesopathy as a separate clinical entity that may coexist but is not caused by low back strain
• Recognize that enthesopathies are often degenerative rather than inflammatory in nature, particularly in sports-related contexts 4
• Be aware that clinical assessment of enthesopathies relies heavily on subjective patient reports and lacks specificity 5

Diagnostic Approach

For suspected enthesopathy:

• Ultrasound with high-frequency transducers is a cost-effective and feasible test for detection 3, 5
• Look for specific radiographic features including bone erosion, hyperostosis, fragmentation, and crystal deposition 2

Treatment Considerations

For enthesopathy:

• Local steroid injections
• Physiotherapy
• Non-steroidal anti-inflammatory drugs
• Treatment of any underlying primary disease 3

For low back strain:

• Standard noninvasive therapies as recommended for nonspecific low back pain 1

Important Caveats

• Unrecognized and untreated enthesopathy can lead to considerable morbidity 3
• The concept of the "enthesis organ" (tissues adjacent to the enthesis that jointly serve stress dissipation) is important for understanding enthesopathies 4
• Consider the muscle-tendon-bone unit as a whole when evaluating musculoskeletal complaints 4

While low back strain and enthesopathy may coexist in some patients, the current medical evidence does not support a direct causal relationship between these conditions.