Enthesis, enthesitis or enthesopathy are terms that many clinicians go through their careers without actually hearing about them. It's something that just isn't discussed that often, and maybe below the radar compared to its better known neighbor. Insertion tendinopathies that have been central to our understanding of injuries at the binding site.
For several years, enthesis-related terms have been increasing both in rheumatological literature and in social media. The limelight deserves to be turned on them, raising awareness of rheumatology, welcoming the scientists who seek answers, and promoting the understanding of those curious physiotherapists who may be particularly interested.
This Physiopsot article is a brief overview of enthesitis and provides useful references for further reading.
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What is an enthesis?
An enthesis is the connective tissue between tendons, ligaments or joint capsule insertions in the bones . There are two types of entheses: fibrous and fibro-cartilaginous (the latter more common in rheumatic diseases; a tough, elastic, compressible tissue). There are entheses all over the body, and examples are indicated by the red circles below. Other entheses mentioned in the literature are the origin and insertion of the patellar tendon, the anterior tibial insertion, the iliopsoas insertion, the insertion of the common hamstring tendons, and the acromial and clavicular insertions of the deltoid muscle.
Enthesitis and enthesopathy
Like many tissues in the body, the pathology can occur for many reasons. Simply put, enthesitis is the term used to describe inflammation of the enthesia, crucially with or without swelling . The presence of it stiffens the tendon / ligament structures and changes the biomechanical load. Enthesopathy, like tendinopathy in tendons, is an umbrella term that is used in the literature to describe any disease process or disorder of an enthesis. Mechanically induced enthesopathy can result from injury and micro-injury and have a degenerative element.
Historically, these pathologies were thought to be focal insertion anomalies at the enthesia site, but this point of view has changed. Benjamin et al. (2004), an enthesis-organ complex is now the preferred reference for enthesis-related pathology, in which more surrounding structures are included in the disease process. It is assumed that the enthesis-organ complex includes not only the enthesis, but also the bursa, the fat pad, the adjacent trabecular bone and possibly even the deep fascia. This may well be the reason why enthesitis is a diffuse process of complications that is beyond the scope of this article.
"It is assumed that the enthesis-organ complex includes not only the enthesis, but also the bursa, the fat pad, the adjacent trabecular bone and perhaps even the deep fascia"
An in-depth review by Kehl and colleagues (2016) examines the molecular, genetic and pathophysiological mechanisms that play a role in enthesitis. Their review found that repeated biomechanical stress causes micro-damage to the enthesis, triggering an inflammatory response in the adjacent synovium, causing synovitis. They also explain the role bacteria play in the immune system response in individuals who are genetically predisposed to the HLA-B27 gene – which is common in rheumatism patients.
Clinical diagnosis and problems in identifying enthesitis
Enthesitis typically presents as pain, stiffness and tenderness of insertions without major swelling. However, swelling can also be a feature of larger lower limb introductions. Enthesitis is clinically diagnosed with pain caused by local pressure on entheseal points or by the use of imaging. Magnetic resonance imaging or ultrasound .
It is assumed that ultrasound is more sensitive in the identification of enthesitis than the clinical examination and can determine certain parts of the affected enthesis organ complex. In addition, there are recommendations on the use of sonography in identifying the most common rheumatic diseases, and this is a useful document for the review of those interested in diagnostic ultrasound and differential diagnosis.
"The enthesis is a relatively avascular structure and therefore inflammation markers must not be increased in entheseal-related disorders"
Clinically, enthesitis can be difficult to recognize without swelling. The enthesis is a relatively avascular structure, so inflammation markers such as ESR or CRP cannot be increased in entheseal-related disorders . In addition, many insertions are either not accessible to the examiner and have poorly localized pain. It is also believed that tender areas of enthesitis are difficult to distinguish from those of fibromyalgia.
The clinical significance of enthesitis | "EAMs"
As discussed in a previous post on extra-articular manifestations, enthesitis is an extra-articular manifestation in some rheumatological conditions associated with spondyloarthritis (SpA). This group of seronegative conditions affect axial and peripheral joints, including: ankylosing spondylitis (or axial spondyloarthropathy), psoriatic arthritis, reactive arthritis, and undifferentiated SpA.
When looking at enthesitis as a central feature of SpA, advanced imaging and pathological findings showed connections between these inflammatory processes and the adjacent osteitis. In SpA, the lower limbs are more frequently affected than the upper limbs, and heel thesitis is the most common site found . In reactive arthritis, enthesitis can be seen in over half of the patients, and in psoriatic arthritis a third of the population is thought to have clinical enthesitis.
Much remains unexplored in relation to enthesis and SpA, although promising progress has been made. It is generally accepted that enthesitis is a key characteristic of SpA and is clearly more than a simple binding site. For all health professionals, understanding the enthesis-organ complex is key to explaining synovitis and osteitis, while pain, stiffness, and other clinical symptoms (erythema, heat, and swelling) may still be the determining factors that our suspects are up to Let enthesopathy arise without imaging.
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This post was originally published in July 2017 and written by Chris Martey . The page has now been updated for freshness, accuracy and completeness.
References
Benjamin, M., Moriggl, B., Brenner, E., Emery, P., McGonagle, D. & Redman, S. (2004) The Concept of the "Enthesis Organ": Why Enthesopathies May Not Occur as Focal Insertion Disorders. Journal of Arthritis & Rheumatism. 50 (10), pp. 3306-3313.
Kehl, A. S., Corr, M. & Weisman, M. H., 2016. Enthesitis: New Insights into Pathogenesis, Diagnostic Modalities, and Treatment. Arthritis & Rheumatology (Hoboken, NJ), 68 (2), p. 312.
McGonagle, D. & Tan, A.L., 2015. The enthesis in psoriatic arthritis. Clinical Expl Rheumatol, 33 (5 Suppl 93), pp. 36-9.
McGonagle, D. & Benjamin, M. (2009) Entheses, Enthesitis and Enthesopathy. Current overviews: Reports on Rheumatic Diseases Series 6, 4, pp. 1-6.
Plagou, A., Teh, J., Grainger, AJ, Schueller-Weidekamm, C., Sudoł-Szopińska, I., Rennie, W., Åström, G., Feydy, A., Giraudo, C., Guerini, H. and Guglielmi, G., 2016, November. Recommendations of the ESSR Subcommittee on Arthritis on Ultrasonography for Inflammatory Joint Disease. In seminars on musculoskeletal radiology (Vol. 20, No. 05, pp. 496-506). Thieme Medical Publishers.
