Knee Tendinopathy, Tendinosis,Tendonitis

Ross Hauser, MD

Tendonitis is a frequent diagnosis in sports medicine that has traditionally been viewed as a tendon injury resulting from repetitive mechanical load, with a subsequent inflammatory response. When the tendon is injured, it tears, inflames, and eventually degenerates because of excess pressure due to underlying joint instability. Chronic tendonitis has sometimes been termed “tendinosis,” reflecting a focus on damage rather than inflammation, which is not found in tendinopathy. Tendinopathy is remarkable for mucoid degeneration and a loss of collagen continuity, which requires appropriate treatment and management regimens, consistent with the degenerative pathology.

The degenerative changes in tendinosis result in loss of tendon strength, decreased load-bearing capabilities, and poor healing potential, all of which lead to further injury and secondary conditions. Common treatments for tendinosis, including NSAIDs and corticosteroids, have been shown to provide little benefit.

Knee tendonitis

Tendonitis is the most common injury to the knee, although not the most well-known one. In general, it refers to an inflammation, irritation or tear of a tendon, the thick fibrous cords that attach muscles to bone.

One of the most frequent types of tendonitis of the knee is pes anserinus tendonitis, which involves the pes anserinus tendons that lie on the inside and just below the knee joint and prevents the lower leg from twisting outward while running. (Below the knee cap, on the inside of the knee, are the attachments of three tendons: semimembranous, semitendinosus, and gracilis. Together, these tendons create the pes anserinus area.)

Middle-aged adult runners are most susceptible to the development of pes anserinus tendonitis, the most common form. Two other types of knee tendonitis are popliteus tendonitis and semimembranous tendonitis.

Patellar tendonitis is inflammation of the patellar tendon, which attaches the kneecap to the tibia or shinbone.The patellar tendon helps your muscles extend your knee.

Popliteus tendonitis is caused by excessive inward rolling of the feet, called pronation, as well as running downhill, which tends to put excessive stress on this tendon and can cause it to tear or become inflamed. Pes anserine tendonitis, on the other hand, is characterized by inflammation of the medial knee, and often coexists with other knee disorders. Semimembranous tendonitis is characterized by swelling over the posteromedial aspect of the knee and tenderness with resisted flexion or outward-turned strain.

Patellar tendonitis is an acute condition, such as knee pain following a run. If the tendon is stressed repeatedly, tiny tears can occur in the tendon. If this process persists, the tendon degenerates causing tendinosis.

Knee tendonitis in general produces pain, tenderness and stiffness near a joint and is aggravated by movement. The inflamed tendons in the knee are usually painful when moved or touched, and the tendon sheaths may be visibly swollen from the accumulation of fluid and inflammation. Moving the joints near the tendon even slightly may also cause severe pain. The pain may be worse when ascending or descending stairs, when getting up from a seated position, and at night.

For the most part, medical intervention, is not needed as the tendon will usually heal itself. HOWEVER, some times the tendon inflammation does not abade and chronic pain develops, This is referred to as chronic tendonitis where inflammation is constantly present or tendonosis where inflammation has given up trying to mend the tendon and joint weakness, mobility issues, and pain persists on a permananet basis.

Most recently, the medical literature began describing problems of the tendons as simply “tendinopathy” or “tendinopathies,” disease of the tendon(s).

Treatments for knee tendinopathies

The typical treatment regime for tendonitis, such as knee tendonitis, rotator cuff tendonitis or patellar tendonitis, includes RICE therapy, ice, non-steroidal anti-inflammatory drugs (NSAIDs), physical therapy and cortisone injections. The problem with this approach is that they do not regenerate or rebuild the weakened tendon and, thus, does not alleviate the chronic pain that people with this condition experience. While ice, anti-inflammatory drugs and cortisone shots have been shown to produce short-term pain benefit, they result in long-term loss of function and even more chronic pain by actually inhibiting the healing process of soft tissues and accelerating cartilage degeneration. If the individual with tendonitis receives cortisone injections into the tendon, or if they take anti-inflammatories for a very long time, the tendonitis will become tendinosis. This means the tendon becomes degenerated.

Other treatment options include cryotherapy and massage. But again, although they may provide pain relief, they do not address the root of the problem – weakened and/or injured tendons and ligaments. When the patient tries these treatment modalities and the pain persists, patients who experience tendonitis may be referred to a surgeon. Unfortunately, surgery has consequences and side effects and may make the problem worse.

Research continues to support the use of Prolotherapy and Platelet Rich Plasma Therapy in the treatment of knee tendinopathies.

Recent research has found:

Platelet Rich Plasma Therapy is effective for knee tendinopathy.(1)
Platelet Rich Plasma Therapy is effective not only for knee tendinopathy but also elbow, shoulder, and Achilles tendon problems,(2) and other tendon problems.(3)
New research shows that a single local injection of PRP coupled with a program of eccentric rehabilitation for treating a chronic jumper’s knee, improves pain symptoms and the functionalities of the subjects’ knee up to 1 year after injection.4
Prolotherapy may be associated with symptom improvement in overuse tendinopathy.6

Tendonitis is a confusing diagnosis

Please see our article Tendinopathy injections and treatments for a general discussion on what is Tendinopathy.

New research says imaging studies confuse the diagnosis.

Australian doctors writing in the Journal of Orthopaedic & Sports Physical Therapy suggest that while damage of the tendon is frequently diagnosed and managed with the clinical use of ultrasound and magnetic resonance imaging there is no direct link between what the MRI says and clinical symptoms, with findings on imaging potentially creating a confusing clinical picture.5

Prolotherapy and Platelet Rich Plasma Therapy

In treating tendonitis, which is occasionally misdiagnosed as bursitis, we recommend stimulating tendon repair and strengthening any weakened or lax ligaments with MEAT treatment, which consists of movement, exercise, analgesics and treatment, as well as herbal supplements. This approach will encourage the damaged tissues to heal as quickly as possible.

Comprehensive Prolotherapy to the knee involves multiple injections of a dextrose-based solution directed at the affected tendons, ligaments and other affected structures of the knee. This causes a mild and localized inflammatory response which triggers the immune system to initiate repair of the injured tendons and ligaments. Blood supply dramatically increases at the injured area. The body is alerted that healing needs to take place and reparative cells are sent to the treated area of the knee that needs healing. The body also lays down new collagen at the treated areas, thereby strengthening the weakened structures. Once the tendons and ligaments are strengthened, the joint stabilizes and the tendonitis or tendinosis condition resolves.

Platelet Rich Plasma Therapy is the use of a patient’s blood platelets and healing factors to stimulate repair of a tendon it is considered when tendon damage is more severe.

As mentioned tendonitis usually does not require Prolotherapy, while tendinosis, the degeneration of the tendon, benefits tremendously from Prolotherapy. However, with tendonitis, if the tendon does not continue to improve every week or if a tendonitis injury requires extra-quick healing, such as is the case with many athletes, Prolotherapy can be performed. When the tendon cannot heal on its own, an underlying ligament problem and joint instability may be occurring, allowing for too much movement of the knee joint. This movement irritates the tendon because the tendon is unable to contract against a stable knee. Prolotherapy strengthens the weakened tendons and ligaments.

1 Lubowitz JH. Editorial Commentary: Biologic Enhancement of Muscle and Tendon Healing. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2015 May 1;31(5):1016. [Google Scholar]
2 Nourissat G, Ornetti P, Berenbaum F, Sellam J, Richette P, Chevalier X. Does platelet-rich plasma deserve a role in the treatment of tendinopathy?. Joint Bone Spine. 2015 Jul 1;82(4):230-4. [Google Scholar]
3. Sanli I, Morgan B, van Tilborg F, Funk L, Gosens T. Single injection of platelet-rich plasma (PRP) for the treatment of refractory distal biceps tendonitis: long-term results of a prospective multicenter cohort study. Knee Surg Sports Traumatol Arthrosc. 2014 Dec 11. [Google Scholar]

4 Kaux JF, Bruyere O, Croisier JL, Forthomme B, Le Goff C, Crielaard JM. One-year follow-up of platelet-rich plasma infiltration to treat chronic proximal patellar tendinopathies. Acta Orthop Belg. 2015 Jun;81(2):251-6. [Pubmed]

5 Docking SI, Ooi CC, Connell D. Tendinopathy: Is Imaging Telling Us the Entire Story? J Orthop Sports Phys Ther. 2015 Sep 21:1-27. [Pubmed]

6 Rabago D, Nourani B. Prolotherapy for Osteoarthritis and Tendinopathy: a Descriptive Review. Curr Rheumatol Rep. 2017 Jun;19(6):34. [Pubmed]