Tendonitis: what is it and what better test to diagnose it?

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Written By Dr. Marcus Yu Bin Pai

MD, PhD. Physical Medicine & Rehabilitation Physician from São Paulo - Brazil. Pain Fellowship in University of São Paulo.

Tendon pain is a common complaint, manifesting in various areas of the body such as the shoulder, knee, or calf.

The term tendonitis is generally used for any type of inflammation in some joint where the tendon is involved. For health professionals, tendonitis can differentiate, characterizing inflammation, degeneration, or injury. Their treatments tend to be different, from immobilization, use of ice and/or heat compresses, anti-inflammatory and analgesics, to surgery.

Thus, in order to accurately identify and evaluate ligaments and tendons for the purpose of controlling an injury and even understanding its evolution, doctors recommend imaging examinations, especially ultrasound and magnetic resonance imaging. Fast, painless methods without ionizing radiation.

Resonance imaging is normally used in more severe cases, such as in a pre-surgical evaluation or in case of deeper injury or parts that cannot be evaluated by ultrasound, such as cartilage, menisci, or non-superficial portions of the bones.

This article aims to provide a more technical understanding of tendon-related conditions, including tendonitis, tendinosis, and strains, as well as bursitis and fasciitis, which are linked to connective tissues.

Tendon Structure and Function

Tendons are dense, fibrous structures that connect muscles to bones, enabling movement and force transmission.

Composed of collagen fibers, tendons exhibit a certain degree of elasticity, which allows for controlled stretching and movement. Tendons consist of primary, secondary, and tertiary bundles, fibrils, and fibers, with a limited number of blood vessels supplying nutrients and oxygen.

This limited blood supply is a crucial factor in the slow healing process of tendons.

Tendon Injuries and Histopathology


Tendon injuries can result from macro trauma, which involves a significant, isolated injury, or micro trauma, which refers to repetitive, smaller injuries over time. Histopathological changes occur in injured tendons, such as fiber disruption, irregular collagen alignment, and scar tissue formation.

Scar tissue disrupts the normal orientation of collagen fibers, compromising the tendon’s tensile strength and increasing the risk of re-injury.

Phases of Tendon Healing

Tendons undergo four distinct phases of healing after an injury:

  1. Inflammation phase: This acute stage is characterized by pain, heat, swelling, and redness at the injury site, usually lasting up to 72 hours.
  2. Regeneration phase: Fibrocytes lay down new tendon fibers in an attempt to repair the injury. This phase can last anywhere from 72 hours to six to eight weeks, depending on the severity of the injury and the individual’s healing capacity.
  3. Remodeling phase: Higher-quality tissue is laid down, and the tendon regains its strength. This phase can take up to 12 months, as collagen fibers reorient and remodel to achieve optimal tensile strength.
  4. End phase: The tendon reaches a state of complete healing, with restored function and strength.

When a tendon fails to heal appropriately, tendinosis—a degenerative condition of the tendon—may develop.

Differences between Tendinitis and Tendinosis

Tendinitis is characterized by inflammation of a tendon, often resulting from excessive use or repetitive strain injuries. The healing process commences with the inflammatory phase, during which the body increases blood flow and delivers immune cells to the affected site. However, if the tendon experiences ongoing irritation or stress, it may become trapped in this inflammatory phase, preventing progression to the repair and remodeling phases of recovery. Consequently, this can give rise to a condition known as tendinosis.

Tendinosis is a specific subtype of tendinopathy, an overarching term for tendon injuries. Distinct from tendinitis, tendinosis involves degeneration of the tendon tissue, which becomes inflamed and of poor quality. This condition can manifest even in young athletes, as exemplified by a 14-year-old baseball player who developed tendinosis after sustaining an injury during winter ball.

Mechanical Stimulation of the Tendon

To promote healing and facilitate the deposition of high-quality tissue, mechanical stimulation of the tendon is essential. Evidence-based research supports the use of mechanical stimulation through techniques such as Graston instrument-assisted soft tissue mobilization or manual manipulation.

These methods can foster tissue repair without exacerbating inflammation. Another efficacious approach for treating tendinosis involves eccentric loading exercises, which consist of lengthening the tendon against resistance. This helps restore elasticity, prevent stiffness, and realign collagen fibers in the tendon structure.

In conjunction with mechanical stimulation and eccentric loading, nutritional interventions can further aid in healing tendinosis. Key nutrients for tendon repair include collagen type 1 fibers, glucosamine, and vitamin C, all of which can be taken as supplements. Additionally, it is vital to maintain inflammation control through appropriate dietary choices and supplementation.


To diagnose tendonitis, healthcare professionals may use different imaging techniques, such as:

  1. Ultrasound: This non-invasive imaging technique can help visualize tendon abnormalities, including inflammation and calcifications2. It can also be used to guide corticosteroid injections for treatment4.
  2. Magnetic Resonance Imaging (MRI): MRI can provide detailed images of tendons and surrounding structures, helping to identify tendonitis and other related conditions3. It is particularly useful in cases where ultrasound results are inconclusive or when a more comprehensive assessment is needed.
  3. X-ray: Although X-rays are not typically the first choice for diagnosing tendonitis, they can sometimes reveal calcifications or other abnormalities associated with the condition5. In some cases, X-rays may be used to rule out other causes of pain, such as fractures or arthritis.
  4. Bone scan: While not a first-line imaging technique for tendonitis, bone scans can provide useful information if they have already been performed for other reasons8.

It is essential to consult a healthcare professional if you suspect you have tendonitis, as they can provide a proper diagnosis and recommend appropriate treatment options.

Evidence-Based Treatment Strategies for Tendon Pain

An effective approach to treating tendon pain should address each phase of the healing process:

  1. Inflammation reduction: Utilize cryotherapy (ice), rest, and anti-inflammatory nutritional supplements, such as systemic enzymes or curcumin, to alleviate inflammation. In some cases, nonsteroidal anti-inflammatory drugs (NSAIDs) may be prescribed for short-term use.
  2. Tendon repair and remodeling: Employ mechanical stimuli, such as myofascial release, active release techniques (ART), and instrument-assisted soft tissue mobilization (IASTM), including Graston technique, to promote proper alignment of tendon fibers during the regeneration and remodeling phases. Additionally, extracorporeal shockwave therapy (ESWT) and low-level laser therapy (LLLT) have shown promise in facilitating tendon healing.
  3. Tendon strengthening and rehabilitation: Implement progressive strengthening and functional rehabilitation exercises, tailored to the individual and the specific tendon involved, once inflammation has subsided and the tendon has begun to heal correctly. This approach should include eccentric exercises, which have been proven to be highly effective in tendon rehabilitation.

Preventing Re-Injury and Long-Term Management

To minimize the risk of re-injury, adherence to a comprehensive rehabilitation plan, including strengthening exercises and regular follow-up with a healthcare professional, is crucial.

Maintenance care, ongoing checkups, and periodic adjustments can contribute to long-term management and prevention of tendon-related conditions. Additionally, consider the following tips:

  1. Maintain proper body mechanics: Ensure correct posture and movement patterns in daily activities and sports to reduce undue stress on tendons.
  2. Modify or vary activities: Avoid repetitive motions or overloading by incorporating cross-training and alternating high- and low-impact activities.
  3. Warm-up and cool-down: Perform dynamic stretching and warm-up exercises before engaging in physical activity, and incorporate static stretching and cool-down activities after completing the exercise.
  4. Gradual progression: Increase the intensity and duration of exercise or training sessions gradually to allow the body to adapt and reduce the risk of overuse injuries.
  5. Wear appropriate footwear: Invest in well-fitted, supportive shoes that are suited to your specific activity and foot type, as improper footwear can lead to imbalances and increased stress on tendons.
  6. Optimize nutrition: Maintain a balanced diet, including essential nutrients and sufficient hydration, to support optimal tendon health and healing. Specific supplements, such as collagen, vitamin C, and omega-3 fatty acids, may also promote tendon health and recovery.
  7. Listen to your body: Pay attention to early signs of discomfort and pain, and address any issues promptly to prevent further damage and chronic conditions.

What about Bursitis and Fasciitis?

Bursitis and fasciitis represent two other soft tissue conditions closely associated with tendon injuries. Bursitis involves inflammation of the bursa, a fluid-filled sac that cushions tendons against bones, preventing friction. In contrast, fasciitis refers to inflammation of the fascia, the dense connective tissue surrounding muscles. These conditions can also be successfully treated with therapeutic interventions such as instrument-assisted soft tissue mobilization, manual manipulation, and specific exercises, all aimed at restoring function and reducing inflammation.

Did you know that…

Health professionals differentiate tendonitis from tendinosis, since tendinosis is the degeneration of a tendon, which may or may not be related to an inflammatory process. Tendinosis is the result of repetitive microtrauma or repetitive inflammation, associated with tissue failure to heal after a tendon rupture.

Tendon rupture is classified according to the thickness of the lesion. Briefly, we consider low-grade ruptures to be ruptures of up to 5%, moderate ruptures range from 5 to 50%, and total ruptures are those greater than 50%. Although it is not a 100% injury, it is difficult for a tendon to regenerate completely when the wear is very large, so its function of contraction or stabilization of the joint may be compromised.


In summary, understanding the intricacies of tendon injuries and their related conditions is crucial for proper diagnosis and treatment. By employing a combination of mechanical stimulation, eccentric loading exercises, and targeted nutritional interventions, it is possible to facilitate healing and recovery in cases of tendinitis, tendinosis, bursitis, and fasciitis.

Tendon pain can significantly impact an individual’s quality of life and athletic performance. A thorough understanding of the underlying mechanisms and healing processes, coupled with evidence-based treatment strategies and prevention measures, is crucial for effectively managing and resolving tendon-related conditions. By adhering to a comprehensive rehabilitation plan and implementing long-term prevention strategies, individuals can optimize tendon health, minimize the risk of re-injury, and maintain an active, pain-free lifestyle.

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MD, PhD. Physical Medicine & Rehabilitation Physician from São Paulo - Brazil. Pain Fellowship in University of São Paulo.

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