Extensor tendon rupture after total knee arthroplasty

Rupture of the extensor mechanism is a rare complication after total knee arthroplasty (TKA). Its effects on patient outcomes and satisfaction are devastating and the treatment is technically challenging. The rupture may be located in the body or at the distal insertion of either patellar or quadriceps tendon. There is a wide range of surgical methods and repair materials. The surgeon needs to identify the best method for each case, which is not always easy. This article provides an overview about the etiology and the most important techniques for repair and reconstruction of a ruptured extensor mechanism.


The incidence of extensor tendon rupture (Figure 1) after TKA has been reported in a range of 1–12% [1, 2]. Their etiology is complex and multifactorial, and poor results emphasize the importance of prevention [3–5]. Often, the rupture occurs during a traumatic event, which may be obvious, eg, a fall on the flexed knee, or trivial, eg, arising from a chair or carrying a heavy weight. Usually, the event causes the rupture because of preexisting fragility in the tendon [6].

The underlying reasons can either be patient-related or structural factors. When patient-related factors are the cause, several years may elapse between the TKA and the tendon rupture. When structural factors are the cause, the rupture often occurs early in the recuperative period [7].

Patient factors include obesity and other comorbidities. Obesity will lead to higher loads on the extensor, which it may not be able to withstand. On the other hand, several systemic diseases have an effect on soft-tissue quality, be it through their impact on blood supply, or through triggering inflammatory processes. Many comorbidities have been implicated in extensor tendon ruptures, including hyperthyroidism, diabetes mellitus, rheumatoid arthritis (RA), connective tissue disorders like systemic lupus erythematosus, and chronic renal failure [6, 8]. Additionally, long-term high-dosage glucocorticoid or fluoroquinolone use, or repeated intraarticular glucocorticoid injections can weaken collagenous tissues, and thus predispose patients for tendon ruptures [3].

Structural factors are often related to prior knee surgeries. To maintain good tissue quality of the extensor tendons in the long run, an optimal blood supply is vital. However, multiple surgical interventions around the extensor mechanism, including distal realignment procedures, will weaken and contribute to reduction of the blood supply [8]. The more extensive the dissection, the higher the compromise of the vascularization.

Yixin Zhou

Beijing Jishuitan Hospital
Beijing, China

Yixin Zhou, Professor and Chairman of Department of Adult Reconstructive Surgery, Beijing Jishuitan Hospital, points out: “Patients with the known relevant comorbidities, with stiff knees and a weak extensor mechanism, as well as male patients over 40 with tendinopathy, should raise red flags for surgeons and make them doubly careful with every maneuver avoiding overtension of the extensor. It is obvious that an impairment of vascularization has deleterious effects on any patient. However, in patients suffering from these conditions, the risk of subsequent tendon failure is so much higher. Therefore, every effort should be undertaken to be as vascularization-sparing as possible.”

Upon performing the TKA surgery, various vascular structures are imperiled (Figure 2). First, the medial and descending genicular arteries are at risk during medial arthrotomy. Second, the lateral-inferior genicular artery and the anterior-tibial recurrent artery are at risk during fat-pad excision. Third, the lateral-superior genicular artery is at risk during release of the lateral retinaculum [6, 8–11].

Figure 2. Blood supply that can be affected during TKA surgery (left). Red lines indicate where the lateral retinacular release (1) and medial parapatellar arthrotomy (2) could endanger the blood supply during TKA surgery (right).


But there are more structural factors than just the blood supply. Tissue weakening may also be caused by the sequela of infection. Stiff knees pose a risk and manipulation under anesthesia may result in extensor tendon ruptures, especially when it is performed with delay [6]. Patellar maltracking can cause increased stresses on the extensor mechanism. Note that Part 1 of this newsletter, on patellar instability, discusses the root causes for patellar maltracking in detail. Additionally, associations with extensor tendon rupture have been reported for patellar overresection [2, 8, 9, 12, 13], overhang of the tibial or patellar component [2, 9, 14], an excessively distal joint-line level [6] as well as an excessively proximal joint-line level causing the tibial plateau to impinge on the patellar tendon [2, 8, 9, 13].

Read the full article with your AO login

  • The importance of tibiofemoral joint stability
  • Surgical techniques
  • Direct repair techniques
  • Tendon reconstruction techniques
  • Outcomes and conclusions

Part 1 | Patellofemoral instability after total knee arthroplasty (TKA)

Part 2 | Patellar fractures after total knee arthroplasty (TKA)

Additional AO resources on this topic

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Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Guillermo Bonilla

Fundación Santa Fe de Bogotá University Hospital
Bogotá, Colombia

Clemens Gwinner

Charité—University Medicine Berlin
Berlin, Germany

Yixin Zhou

Beijing Jishuitan Hospital
Beijing, China

This issue was  written by Elke Rometsch, AO Innovation Translation Center, Clinical Science, Switzerland.


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