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Tendonitis and Tendinopathy - What you need to know about common tendon injuries

Tendonitis and tendinopathies are common orthopedic problems. Tendonitis symptoms can vary. Some are mild and nagging. Others are debilitating. This article will explain what happens to damaged tendons. It will review treatment options for tendonitis and tendinopathies. It will also explore novel ways to treat these common problems.

What are tendons?

Tendons connect muscle to bone. They pass on the force generated by a muscle contraction to move bones. Tendons are composed of a tight network of protein called collagen. These organized units are what give tendons their strength.

Tendon Cells

Tenocytes and tenoblasts are the main cells that make up tendons. These two cells are responsible for maintaining the integrity of the tendon. They also provide energy to support tendon function.

Oxygen consumption of tendons is significantly lower than muscles. Tenocytes have an extraordinary capacity to generate energy in low oxygen environments. This is crucial to transmit heavy loads for long periods of time.

Blood supply to tendons is generally poor. They get most of their blood supply from surrounding muscles (where tendons originate) and bones (where tendons insert). Because of this, tendons have a watershed area with poor blood supply. Injuries heal very slowly because tendons consume little oxygen and have poor blood supply.

Tendon injuries heal very slowly because they have poor blood supply.

Take for example the Achilles tendon. This is a thick band of tissue that connects the calf muscles to the heel. High levels of tension are transmitted through the Achilles tendon. Because the Achilles tendon is so long, it has a large section in the middle of the tendon with poor blood supply. This occurs about 2 to 7 cm above the heel. This is the exact area where Achilles tendinopathy occurs.

Tendon Damage

All tendons have a carrying threshold. Loads greater than this threshold will result in acute tendon damage. This leads to inflammation within the tendon called tendonitis. Extreme loads can lead to a tendon tear.

Tendon Healing

Acute tendon injuries heal in four main phases: hemostasis, inflammation, proliferation, and maturation.

Hemostasis involves stopping a bleed. It occurs immediately after an injury. Platelets are the key cells involved in hemostasis. They clump up to form a blood clot. They also release small signaling proteins called cytokines. Cytokines recruit other cells important for tissue repair and tissue healing. One of the most important cytokines released by platelets is platelet derived growth factor (PDGF). PDGF recruits cells involved in healing. Platelet rich plasma relies upon the powerful signaling properties of PDGF.

After the bleeding stops, inflammation takes over. This phase involves redness, warmth, swelling, and pain. It occurs in the first 1-2 days after an injury. The goal of this step is to prevent infection. White blood cells clean the injury site and kill off bacteria. They also release cytokines and growth factors needed for tissue repair.

Once the site is cleaned, the injury is ready for the proliferation phase. This occurs within the first few days after an injury. Tenocytes begin to lay down a foundation of collagen. This foundation will mature and remodel. Their fibers align and form cross links to build stronger tissue. Remodeling is an ongoing process. It can take up to one year for new tissue to gain its strength.

Chronic Tendon Injuries

Nontraumatic injuries are less understood.

Chronic repetitive injuries and overuse injuries cause significant pain and disability. Many factors contribute to these injuries. Form and function play a crucial role. For example, people who pronate their feet have higher rates of Achilles tendinopathy.

Tendon overloading also contributes. Frequent repetitive movements cause microtrauma to the tendons. This is not a problem if the tenocytes have enough time to repair. However, accumulation of microtrauma leads to weak tendons. And weak tendons are susceptible to tears.

Frequent repetitive movements cause microtrauma to tendons. Accumulation of microtrauma leads to weakness and pain.


Tendinopathy describes the process of tendon weakening and degradation. Many clinicians use the term “tendonitis” to describe pain from chronic tendon dysfunction. This is incorrect as the ending “-itis” implies an inflammatory process. Histological analysis shows that inflammation is only seen in acute injuries.

Tendinopathy tendon fibers are unorganized and degenerated. They have poor strength and altered function.

Sharma et al (JBJS, 1/2005) summarizes “histological examination of tendinopathy shows disordered, haphazard healing with an absence of inflammatory cells, a poor healing response, noninflammatory intratendinous collagen degeneration, fiber disorientation and thinning, hypercellularity, scattered vascular ingrowth, and increased interfibrillar glycosaminoglycans.”

What does this all mean?

When we look at tendinopathy under a microscope, there are no inflammatory cells. We see unorganized and degenerated fibers. These degenerated fibers have poor strength and altered function. Chemical analysis also shows greater levels of pain neurotransmitters compared to normal tendons.

Musculoskeletal Ultrasound to Diagnose Tendinopathy

Diagnostic ultrasounds are an excellent modality to supplement the physical exam. Healthy tissue and diseased tissue appear different under ultrasound. Tendinopathies have distinct ultrasound characteristics. Tendons appear dark and thick. Both are signs of fiber disorientation and degeneration.

This is an ultrasound image of severe achilles tendinopathy. Imagine someone lying down with their achilles tendon flat on a surface. The left of the image would be towards the head and the right of the image is towards the heel. The orange arrow represents the thickness of this achilles tendon. It is extremely thick compared to a normal achilles tendon. The blue arrow represents the portion of the tendon that is still normal and healthy. Notice the fibers are all aligned and appear bright white. The red arrow represents areas of tendinopathy. The fibers here are much darker in appearance.

Tendon Disease Nomenclature

We need to be careful how we describe common orthopedic conditions. I offer some suggestions below.

Common Tendinopathies. Rotator cuff tendinopathy. Elbow tendinopathy. Wrist tendinopathy. Gluteal tendinopathy. Patellar tendinopathy. Achilles tendinopathy. Ankle tendinopathy.
  • Lateral epicondylitis (tennis elbow) → lateral epicondyle tendinopathy

  • Medial epicondylitis (golfer’s elbow) → medial epicondyle tendinopathy

  • Rotator cuff tendonitis → rotator cuff tendinopathy

  • Achilles tendonitis → Achilles tendinopathy

  • Patellar tendonitis (jumper’s knee) → patellar tendinopathy

  • Trochanteric bursitis → gluteal tendinopathy

How we name these conditions actually affects treatment. Lateral epicondylitis implies an inflammatory disease. Inflammation can be treated with oral anti-inflammatory medications such as ibuprofen and naproxen. Inflammation can also be treated with cortisone injections. Cortisone has powerful anti-inflammatory properties.

How well do cortisone injections work for “tendonitis” or tendinopathy? Not well. Click here to learn more about cortisone injections and their toxicities.

Treatment Options for Tendinopathies

Tendinopathies are generally treated conservatively. A brief period of rest and bracing help to reduce stress and strain on the affected area. It is important to keep any immobilization period as brief as possible. Prolonged immobilization leads to joint stiffness as well as muscle atrophy. This is counterproductive to healing.


The most important aspect of treatment is to address form and function. A biomechanical problem that causes increased wear and tear needs to be addressed. Many studies support home exercise programs and physical therapy.

Rehabilitation is focused on form and function. This involves stretching exercises and progressive tendon loading.

Histological analysis of tendinopathy reveals collagen degeneration and fiber disorientation. A structured exercise regimen built on concentric and eccentric exercises provides progressive loads through a tendon. This leads to fiber reorientation, tissue remodeling, and tissue healing.

It is important to be mindful that tendons take time to heal. A tendon can take up to one year to regain its strength after an acute injury. Chronic tendinopathies do not develop overnight. Rehabilitation and home exercise programs often take months to be completely symptom free.

Orthobiologics and Platelet Rich Plasma Injections

Despite these conservative measures, many people continue to have pain from tendinopathies. Many clinicians and patients think cortisone injections are the next step. But numerous studies have shown the negative effects of steroids in tendons. Orthobiologics such as platelet rich plasma are an excellent treatment option.

Platelets contain an enormous amount of bioactive molecules. The most important one is platelet derived growth factor. PDGF recruits cells to speed up recovery, stimulate tissue healing, and provide pain relief. A large infusion of PDGF has tremendous healing potential. This is especially true if injected into a degenerated tendon.

Platelets contain an enormous amount of bioactive molecules involved in stimulating tissue healing and providing pain relief.

Randomized controlled trials comparing PRP injections to cortisone injections show a clear favorite.

PRP injections are superior.

Platelet Rich Plasma to Treat Elbow Tendinopathies (Tennis Elbow and Golfer’s Elbow)

For treatment of tennis elbow and golfers elbow, PRP injections provide significant improvements in pain scores when compared with steroid injections.

Huang et al (Am J Sports Med, 12/2019) published a systematic review and meta-analysis looking at PRP injections vs cortisone injections for elbow tendinopathies. They included 9 randomized controlled trials into their data set for a total of 565 patients.

The authors concluded that for elbow tendinopathies, “PRP injections provide a statistically and clinically meaningful long-term improvement in pain scores, whereas corticosteroid injections provide a statistically meaningful but not clinically significant short-term reduction in pain scores.”

Platelet Rich Plasma to Treat Gluteal Tendinopathies

For treatment of gluteal tendinopathy, PRP injections outperform steroid injections in pain and function.

Fitzpatrick et al (Am J Sports Med, 4/2019) published a double blinded randomized controlled trial comparing PRP injections with cortisone injections. They randomized patients to a leukocyte rich PRP injection or a cortisone injection.

The authors found that the leukocyte rich PRP injection group improved significantly in pain and function as assessed by the modified Harris Hip Score when compared to the cortisone injection group at 12 weeks, 24 weeks, 1 year, and 2 years.

They write that “among patients with chronic gluteal tendinopathy and a length of symptoms >15 months, a single intratendinous leukocyte rich PRP injection performed under ultrasound guidance results in greater improvement in pain and function than a single corticosteroid injection. The improvement after leukocyte rich PRP injection is sustained at 2 years, whereas the improvement from a corticosteroid injection is maximal at 6 weeks and not maintained beyond 24 weeks.”

Why Platelet Rich Plasma Works in Treatment of Tendinopathies

If we stop and think about pathophysiology, it makes sense why they work.

Tendinopathies are degenerative conditions. Histology shows poor healing response, collagen degeneration, and tissue thinning. A large bolus of platelet derived growth factor from PRP kick starts the healing process. Most important, studies show PRP injections provide sustainable pain relief and tissue healing.

Discuss with your doctor the best way to treat your tendinopathy. Home exercise programs and physical therapy are excellent first line options. However, if pain persists, consider a PRP injection and avoid the toxicities of steroid injections.


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