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Patellar Tendonitis

Patellar tendinitis pain can be quite deceptive. It is produced by strenuous physical activity and after a while, the pain decreases. Then, when you return to rest, the pain returns with even more force than before.

“The tendon is a metabolically active tissue which responds to mechanical stresses in the same way as bone or muscle. When a tendon is subject to a force greater than its resistance, microruptures can occur inside. These lesions may heal completely and disappear, or they may heal partially and develop towards a chronic tendinitis with scar tissue, calcifications and cysts, presenting symptoms of pain and functional impairment. The intratendinous changes are endogenous and do not suggest an external force acting on the tendon. In fact, most of the chronic inflammatory conditions in tendons are of endogenous aetiology, e.g. the patellar tendinitis which is caused by overuse of the knee extensor mechanism. Among the many causes of anterior knee pain patellar tendinitis is a well-defined entity.”1

“The patellar tendon (PT) is becoming increasingly important in modern surgical practice. Anatomical texts provide only short descriptions, often limited to its surface. In addition, the etiopathogenetic hypothesis of patellar tendonitis is still a subject of debate. A detailed knowledge of bundle orientation, attachments’ morphology, apex position relative to the tendon and shape of the tendon is required in order to better understand the pathogenesis of patellar tendonitis.”2


Posterior aspect of the patella
Fig. 1. Posterior aspect of the patella, after splitting the synovial covering and fat pad. The ‘bare’ (non-articular) area can be seen, distal to the articular surface, in the midpart of the photograph. The back of the patella tendon can be seen in the lower part of the photograph. Reprinted from: Reprinted from “The anatomy of the patellar tendon.” Knee surgery, sports traumatology, arthroscopy, 9(1), 2-5. By Basso, O., Johnson, D. P., & Amis, A. A. (2001).
Posterior aspect of the PT of one of the specimens presenting a ridge of fibers
Fig. 2. Posterior aspect of the PT of one of the specimens presenting a ridge of fibers. This attached to the distal area of the posterior aspect of the patellar apex which is seen in the upper part of the photograph. Reprinted from “The anatomy of the patellar tendon.” Knee surgery, sports traumatology, arthroscopy, 9(1), 2-5. By Basso, O., Johnson, D. P., & Amis, A. A. (2001).


Patellar tendinitis is popularly known as ‘jumper’s knee’. This is because it is a frequent condition in those who perform sports activities that require continuous jumping such as basketball or volleyball. Other names for patellar tendinitis are patellar tendinopathy or patellar tendonitis. It occurs as a result of repetitive movements that cause damage, overload, or tissue irritation affecting the patellar tendon. This tendon is essential for the balance and flexibility it provides. Hence, when these types of conditions happen, the knee articulation becomes much more rigid and therefore, dysfunctional.

The patella rests on the front of the knee joint. When someone contracts or extends the knee, the lower area of the kneecap slides over the bones in that area. There are two tendons whose main function is to help fix the patella to the bones and muscles that support the knee. These tendons are the patellar tendon and the quadriceps tendon. When one of these becomes inflamed, the kneecap loses functionality. Therefore, there is an impairment of the normal movement of the joint. The resulting pain can be very severe.

Pathology and pathophysiology

“The predominant pathological feature of patellar tendinopathy is tendinosis, typically in the deep posterior portion of the patellar tendon adjacent to the lower pole of the patella. Tendinosis is characterized by progressive tissue degeneration with a failed reparative response and the complete absence of inflammatory cells. Macroscopically, this makes the afflicted region of the tendon soft and gives it a yellow-brown, disorganized appearance—an appearance that is commonly labeled ‘mucoid degeneration’. This contrasts with the normal appearance of a glistening, stringy, parallel-organized, white tendon.

When viewed microscopically, the pathological region is distinct from normal tendon, with both matrix and cellular changes. Instead of clearly defined, parallel, and slightly wavy collagen bundles, tendinopathy is associated with relative expansion of the tendinous tissue, loss of the longitudinal alignment of collagen fibers, and loss of the clear demarcation between adjacent collagen bundles. The tissue has lost its normal reflective appearance under polarized light, and there is gradual and increasing separation of collagen fibers that distorts the normally dense homogenous polarization pattern. Occasional clefts in the collagen suggest microtears that may be interpreted as microscopic partial ruptures. In addition, there are frequently focal regions of intratendinous calcification. The latter may arise due to traction injury to the inferior pole of the patella; however, recent evidence has shown the calcification to have formed discretely via endochondral ossification.

Multiple cellular changes coexist with the matrix changes in tendinopathy. The most obvious of these changes is hypercellularity resulting from an increase in cellular proliferation. There is atypical fibroblast and endothelial cellular proliferation, and extensive neovascularization. These changes represent an attempt at healing. The collagen-producing tenocytes lose their fine spindle shape, and their nuclei appear more rounded and sometimes chondroid in appearance, indicating fibrocartilaginous metaplasia. Of note is the consistent finding of a clear absence of inflammatory cells.”3

Causes of Patellar Tendinitis

An inadequate, constant and repetitive movement stresses the tendon and causes it to become inflamed. This is called micro trauma by repetition and is common in athletes. Other frequent causes of patellar tendinitis are when:

  • The patella is located higher than normal
  • Quadriceps muscles present weakness and a lack of flexibility
  • An injury occurs and it’s not treated properly
  • There is excessive stress put on the knee. “The clinical evaluation of the knee is a fundamental tool to correctly address diagnosis and treatment, and should never be replaced by the findings retrieved by the imaging studies carried on the patient.

Every surgeon has his own series of exams with whom he is more confident and on whom he relies on for diagnosis. Usually, three sets of series are used: one for patello-femoral/extensor mechanism pathologies; one for meniscal and chondral (articular) lesions; and one for instability evaluation.”4

  • Muscle fatigue is present. “Muscles that are used intensively show a progressive decline of performance which largely recovers after a period of rest. This reversible phenomenon is denoted muscle fatigue. The phenomenon must have been recognized by perceptive observers since posterity, but studies of the mechanism are relatively recent.”5
  • Inadequate footwear is used

“Patellar tendinopathy is primarily a condition of relatively young (15-30 years old) athletes, especially men, who participate in sports such as basketball, volleyball, athletic jump events, tennis, and football, which require repetitive loading of the patellar tendon. The power needed for jumping, landing, cutting, and pivoting when participating in these sports requires the patellar tendon to repetitively store and release energy. Energy storage and release (similar to a spring) from the long tendons of the lower limb are key features for high performance while reducing the energy cost of human movements. Repetition of this spring-like activity over a single exercise session, or with insufficient rest to enable remodeling between sessions, can induce pathology and a change in the tendon’s mechanical properties, which is a risk factor for developing symptoms. Energy-storage load is defined in this article as high tendon load, because it is associated with tendon injury.”6

Symptomatically, you feel a discomfort when you bend your knees. Usually, the pain appears when the movement starts, but then disappears when physical activity is performed. When returning to rest, the pain returns.

The main symptom of patellar tendonitis is pain, felt just below the kneecap. There is also a feeling of tension and stiffness in the knee. There are also many people who experience pain in the upper portion of the knee, mainly appearing when the muscles of that area are tensed. As noted, the pain goes away when you exercise, but then it reappears. If left untreated, the discomfort will become permanent.

Most often, patellar tendinitis is diagnosed based on the medical history and a physical examination. X-rays are sometimes ordered to confirm the diagnosis and only in very exceptional cases an MRI is indicated.

“The diagnosis is based on the history and the clinical examination, and is complemented by radiographic, ultrasound and magnetic resonance imaging (MRI) examinations. Radiography shows the morphology of the inferior pole of the patella and may show calcifications in the tendon, while ultrasonography and MRI may show structural and inflammatory alterations of the tendon, such as thickening, degeneration and tears. The initial treatment is conservative, with the aims of pain relief and functional recovery. It begins with institution of relative rest, modification of activities and control over predisposing factors, in association with use of medications and physiotherapy. This is effective is most cases, but with a risk of recurrence. Functional rehabilitation consists of analgesic and anti-inflammatory measures in association with mechanical therapy consisting of eccentric strengthening and specific stretching.

Other treatment options such as injection of corticosteroids are also used, although many authors present divergent opinions regarding their efficacy and safety. Application of platelet-rich plasma has been gaining more followers, but the results presented remain inconclusive. Surgical treatment is indicated in cases that evolve with persistent pain and functional limitation after a minimum period of 6 months of well-executed conservative treatment. The presence of structural alterations of the tendon and impact with the lower pole of the patella are factors relating to failure of conservative treatment.

The surgical treatment consists of debridement of the degenerated tissue by means of longitudinal cuts in the tendon and abrasion of the inferior pole of the patella.”7

“Arthroscopic surgery for patients with patellar tendinopathy, refractory to nonoperative management, appears to provide significant improvements in symptoms and function, with improvements maintained for at least 3 years. These results suggest that some patients may not be able to achieve their presymptom sporting level; or if they do, they may participate in sports with some degree of residual symptoms.”8

The first pain control measure is rest to reduce inflammation. Sometimes, it is necessary to immobilize the area, using a patellar band or knee brace. This provides the knee support and helps keep it immobilized. Analgesics and anti-inflammatories should certainly be considered, as long as they are advised by a physician or practitioner.

“Physical examination during all stages reveals tenderness to palpation and pain over the inferior pole of the patella   and possibly in the body of the tendon.   Thickness of the tendon may be noted also in all stages, but it is rare to see effusion. Pain in the patellar tendon may be reproduced with resisted knee extension. Additional functional tests of ascending or descending stairs, performing single leg declining squats, jumping or hopping will most likely reproduce patellar pain symptoms. Patients such as weight lifters may complain of a ‘giving way’ or a perception that knee will ‘buckle’ under load as well as stiffness or achiness after activity. Additionally, they may complain of stiffness or achiness after activity”9

Using cold therapy is reported to help a lot to mitigate pain. It can be a little uncomfortable but is well worth it. To treat the knee, place some ice covered with cloth on the affected area several times a day. When doing so, make sure to lift the leg and hold it up for a few minutes when the pain appears while icing down the knee.

“It has been shown that eccentric exercises are one of the fundamental treatment types in the rehabilitation of patellar tendinopathy, given that they increase the tendon’s resistance to traction, producing an elongation of the tendinous muscle unit, thus meaning the tendon bears less tension. Some of the physiological effects of the exercises on the tendon have been proven. They are effective in encouraging the formation of tendon collagen fibers, improving its remodeling and requiring less oxygen consumption, greater muscle tension and less energy expenditure.”10

Only when conservative treatment does not work and patellar tendonitis becomes chronic is it recommended to treat the ailment with surgery, where the damaged part of the tissue that is inflamed is extracted. Sometimes, small cuts are made just on the sides of the tendon to decrease the pressure.



(1) Fritschy, D., & Wallensten, R. (1993). Surgical treatment of patellar tendinitis. Knee Surgery, Sports Traumatology, Arthroscopy, 1(2), 131-133. Available online at

(2) Basso, O., Johnson, D. P., & Amis, A. A. (2001). The anatomy of the patellar tendon. Knee surgery, sports traumatology, arthroscopy, 9(1), 2-5. Available online at

(3) Brukner, P. (2003). Patellar tendinopathy. Clin Sports Med, 22, 743-759. Available online at

(4) Rossi, R., Dettoni, F., Bruzzone, M., Cottino, U., D’Elicio, D. G., & Bonasia, D. E. (2011). Clinical examination of the knee: know your tools for diagnosis of knee injuries. Sports Medicine, Arthroscopy, Rehabilitation, Therapy & Technology, 3(1), 25. Available online at

(5) Allen, D. G., Lamb, G. D., & Westerblad, H. (2008). Skeletal muscle fatigue: cellular mechanisms. Physiological reviews, 88(1), 287-332. Available online at

(6) Malliaras, P., Cook, J., Purdam, C., & Rio, E. (2015). Patellar tendinopathy: clinical diagnosis, load management, and advice for challenging case presentations. journal of orthopaedic & sports physical therapy, 45(11), 887-898. Available online at

(7) Cenni, M. H. F., Silva, T. D. M., do Nascimento, B. F., de Andrade, R. C., Júnior, L. F. B. P., & Nicolai, O. P. (2015). Patellar tendinopathy: late-stage results from surgical treatment. Revista Brasileira de Ortopedia (English Edition), 50(5), 550-555. Available online at

(8) Pascarella, A., Alam, M., Pascarella, F., Latte, C., Di Salvatore, M. G., & Maffulli, N. (2011). Arthroscopic management of chronic patellar tendinopathy. The American journal of sports medicine, 39(9), 1975-1983. Available online at

(9) Rutland, M., O’Connell, D., Brismée, J. M., Sizer, P., Apte, G., & O’Connell, J. (2010). Evidence–supported rehabilitation of patellar tendinopathy. North American journal of sports physical therapy: NAJSPT, 5(3), 166. Available online at

(10) Díaz, J. J. G. Effectiveness of eccentric exercise in patellar tendinopathy. Literary review. Available online at


Robert Velasquez
13 October, 2018

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Hello everyone, my name is Robert Velazquez. I am a content marketer currently focused on the medical supply industry. I studied Medicine for 5 years. I have interacted with many patients and learned a more:

4 thoughts on “Patellar Tendonitis

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