Patellar Tendon Rupture Case File
Eugene C. Toy, MD, Andrew J. Rosenbaum, MD, Timothy T. Roberts, MD, Joshua S. Dines, MD
CASE 7
A 26-year-old African American male athlete reports to clinic after injuring his knee the night before while he was practicing squats and dead lifts for his upcoming weightlifting competition. He states he felt a “pop” as he began to stand during his second set of squats. He complains of intense pain and an inability to lift his leg or bear any weight on it. These symptoms began immediately after the pop. During the physical examination, the patient is found to have pain with palpation just below the patella. Although he is found to have good quadriceps tone, he is unable to perform a straight leg raise. All motor and sensory findings are otherwise normal. It is decided that radiographs should be obtained, which subsequently show patella alta. His past medical history and review of systems are otherwise unremarkable.
► What is the most likely diagnosis?
► What is the best treatment for this condition?
ANSWER TO CASE 7:
Patellar Tendon Rupture
Summary: A 26-year-old African American male athlete who is a competitive weightlifter injured his left knee while performing dead lifts in the gym. He felt a pop in his knee and reported pain with considerable swelling to the anterior aspect. He has pain with palpation over the inferior pole of the patella and is unable to perform a straight leg raise, even though he has good quadriceps tone. All motor and sensory findings are otherwise normal. An x-ray identifies patella alta. His past medical history and review of systems are otherwise unremarkable.
- Most likely diagnosis: Patellar tendon rupture
- Treatment: Surgery for patellar tendon repair within 2 weeks. Before surgery, he is to ice and elevate his leg to help diminish the local swelling. The leg should be braced in extension to minimize further gapping and proximal retraction of the patella. After surgery, the leg will be protected in extension followed by gradual, progressive range-of-motion exercises.
ANALYSIS
Objectives
- Learn the causes of patellar tendon rupture.
- Understand the prevalence of the injury.
- Be familiar with the populations that are most often affected.
- Understand the therapy options.
Considerations
This is a 26-year-old African American male athlete who has presented with a story, physical exam, and radiographic findings consistent with a patellar tendon rupture. Although his story identifies repetitive microtrauma as the likely cause of his patellar tendon rupture, other predisposing factors must be investigated. In the setting of a competitive weightlifter, such as this gentleman, anabolic steroid use as a contributing factor should be contemplated. Because this is an acute rupture in a healthy young adult, surgical repair is indicated within 2 weeks from the date of injury. Surgical technique will vary based on the location of the rupture. Because most tears occur at the osseotendinous juncture between the tendon and inferior pole of the patella, bone tunnels and heavy suture will likely be required. It is also important to note that although no palpable gap was felt below the inferior patellar pole on physical exam, this would not be an uncommon finding.
APPROACH TO:
Patellar Tendon Rupture
DEFINITIONS
TENDINITIS: A term describing tendon inflammation.
TENDINOSIS: A term referring to chronic inflammation of a tendon, in which damage occurs at the cellular level. It is thought to be caused by repetitive microtrauma that increases the chance of a tendon rupture.
JUMPER’S KNEE: A phrase used to describe patellar tendon pathology, including tendonitis and tendinosis. These conditions typically occur in athletes involved in jumping sports such as basketball and volleyball and are therefore referred to as Jumper’s knee.
BLUMENSAAT LINE: A line drawn along the roof of the intercondylar notch on a lateral radiograph with the knee in 30 degrees of flexion. This line should intersect the inferior border of the patella. In patella alta, which occurs in the setting of a patella tendon rupture, the distal pole of the patella is elevated above this line.
INSALL-SALVATI RATIO: Determined on a lateral radiograph and is the length of the patella tendon/length of the patella (the greatest diagonal length). The relationship should be 1.0. A ratio of 1.2 or more indicates patella alta, whereas a ratio of less than or equal to 0.8 indicates patella baja (seen in the setting of a quadriceps tendon rupture).
EXTENSOR MECHANISM OF THE KNEE: A network consisting of the quadriceps musculature, quadriceps tendon, patella, patellar tendon, tibial tubercle, and adjacent soft tissues that serves to extend or straighten the knee joint with the leg elevated and to stabilize the knee joint when the foot is planted on the ground.
CLINICAL APPROACH
Etiology
The patella’s role in the extensor mechanism is to establish a mechanical advantage in knee extension by increasing the moment arm of the quadriceps muscle. For the patellar tendon to rupture, an eccentric and violent quadriceps contraction must occur with the knee partially flexed. Less frequently, penetrating trauma can cause a tear. Ruptures can be classified as complete or incomplete and as intrasubstance or as occurring at the insertion site of the tendon onto the inferior pole of the patella (an avulsion-type injury). Tendon avulsion from the tibial tuberosity is encountered less frequently.
It is uncommon for the patellar tendon to rupture in healthy tendon, and when it does, it is most commonly due to repetitive microtrauma. Although there is no clear age or sex predisposition for this injury, it is more commonly seen in those with an underlying disease that causes weakness in the tendon, predisposing it to rupture. Such diseases include rheumatoid arthritis, diabetes, lupus, gout, and chronic renal insufficiency. The tendon may also become weakened from anabolic steroid use or chronic use of corticosteroid medication injected directly into the tendon.
Physical Examination
The patient typically presents with a gross deformity of the knee, which includes an effusion and proximal retraction of the patella when compared with the contralateral, normal knee. Palpation may reveal an intrasubstance defect or one at its inferior pole. With an acute tear, the patient will have difficulty weightbearing, and the knee may buckle or feel as if it is going to “give out.” When asked, the patient may recall an audible “pop” that had occurred at the time of injury and may be unable to perform a straight leg raise. However, one’s ability to perform a straight leg raise does not completely rule out the presence of a patellar tendon rupture. In certain cases, the tendon can be ruptured while the adjacent medial and lateral retinacula of the knee remain intact, enabling the patient to perform some active extension. In such cases, the patient will, however, likely lack several degrees of terminal extension.
Radiographic Diagnosis
Anteroposterior (AP) and lateral radiographs are usually sufficient in confirming the diagnosis. The Blumensaat line and the Insall-Salvati ratio are derived from the lateral radiographs and aid in identifying both quadriceps and patellar tendon injury ( Figure 7–1 ). At times, it may be useful to obtain a lateral radiograph of the contralateral knee for comparison. In equivocal cases in which diagnosis is unclear, ultrasound or magnetic resonance imaging (MRI) can be used. MRI can distinguish complete from partial ruptures, assist in determining the size of the tear, and also identify any concomitant injuries.
Figure 7–1. A lateral radiograph of a normal knee. The distal pole of the patella intersects Blumensaat
line (A), and the Insall-Salvati ratio is approximately 1.0 (B/C).
TREATMENT
Nonoperative treatment is limited to incomplete ruptures in which normal or nearnormal knee extension is present. In such cases, management consists of immobilization with the knee in full extension for 4 to 6 weeks. Acute, complete tears require surgical repair unless there is a medical contraindication. It is ideally performed within 2 weeks of the initial injury to prevent further tendon retraction, scar formation, and muscle atrophy. Midsubstance tears are repaired end to end with a heavy nonabsorbable suture. However, ruptures most commonly occur at the osseotendinous juncture, a location that is not amenable to end-to-end repair. In this setting, the patellar tendon is reattached to its insertion using bone tunnels and heavy suture. The repair can be augmented with a cerclage suture, as is often done for midsubstance tears, in patients with systemic illnesses that have predisposed them to rupture (ie, diabetes), or in those who will likely undergo aggressive early postoperative range-of-motion exercises. Postoperative rehabilitation protocols vary from surgeon to surgeon. A common practice is to immobilize the leg in extension for 10 to 14 days, followed by progressive, protected range of motion. Isometric quadriceps strengthening may begin immediately postoperatively. The return to full activity could take up to 6 to 12 months. Furthermore, the patient will be allowed to return to sports only after a complete return of strength and range of motion has occurred.
Chronic ruptures are more difficult to repair and typically result in less favorable outcomes, as tendon degeneration and contraction make end-to-end apposition difficult to achieve. Surgery involves extensive mobilization of the tendon, lysis of scar tissue, and at times the use of an interposition flap or graft to bridge the gap and achieve a complete repair. This is a technically more demanding procedure and is less than ideal.
Complications
Complications include wound infection, patellofemoral arthritis, rerupture, and loss of knee motion. Difficulty in attaining full extension is most commonly due to quadriceps atrophy, highlighting the importance of early postoperative quadriceps strengthening.
COMPREHENSION QUESTIONS
7.1 A 22-year-old basketball player feels a painful “pop” in his knee when landing from a rebound. Immediate swelling, pain, and inability to extend his knee ensue. Radiographs depict patella alta. Treatment should include:
A. Long leg casting in extensionB. Application of a knee immobilizer followed by a slow return to playC. Primary patella tendon repairD. Intraarticular corticosteroid injection
7.2 Which of the following structures is not part of the knee’s extensor mechanism?
A. Quadriceps tendonB. Patella tendonC. Biceps femorisD. Tibial tubercle
7.3 A 55-year-old male slips on a patch of ice and falls on a hyperflexed knee. He reports hearing a “pop” during the fall and was unable to bear weight on the knee immediately after the injury. He has a large knee effusion on examination and is unable to perform a straight leg raise. You appreciate his patella baja on radiographic examination and an Insall-Salvati ratio of 0.7. What is the likely diagnosis?
A. Patellar dislocationB. Quadriceps tendon ruptureC. Patellar tendon ruptureD. Anterior cruciate ligament (ACL) tear
ANSWERS
7.1 C. Sports such as basketball, football, soccer, and volleyball place high eccentric loads on the extensor mechanism and are associated with patellar tendon rupture. Primary surgical repair is always indicated for complete, acute tears.
7.2 C. The biceps femoris is not part of the extensor mechanism, but instead performs knee flexion. The other muscles are part of the knee extensor mechanism.
7.3 B. The differential diagnosis for any patient with a history of recent trauma to the knee and an inability to straight leg raise must include both quadriceps and patellar tendon ruptures. In patients older than 40 years, such as this patient, quadriceps tendon ruptures are more common; patella tendon ruptures are more frequently seen in patients younger than 40 years. The diagnosis of a ruptured quadriceps tendon is also supported in this patient by the radiographic finding of patellar baja and an Insall-Salvati ratio of less then 0.8. Both ACL and acute dislocations of the patella occur after noncontact pivoting injuries, making such diagnoses unlikely in this patient. Although physical exam may reveal large knee effusions in such patients, they should not lose their ability to actively straight leg raise.
CLINICAL PEARLS
► The patella’s role in the extensor mechanism is to establish a mechanical advantage in knee extension by increasing the moment arm of the quadriceps muscle. ► Patellar tendon ruptures result from eccentric and violent quadriceps contraction occurring with the knee partially flexed. ► It is uncommon for the patellar tendon to rupture in healthy tendon. ► Nonoperative treatment is limited to incomplete ruptures in which normal or near-normal knee extension is present. ► Midsubstance tears are repaired end to end with a heavy nonabsorbable suture. ► Rupture at the osseotendinous juncture requires repair with bone tunnels and heavy suture. ► Acute patellar tendon tears should be repaired within 2 weeks from the injury. |
REFERENCES
Frontera WR, Silver JK, Rizzo TD. Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and Rehabilitation . Philadelphia, PA: Saunders Elsevier; 2008:xix, 935 p.
Judd SJ. Sports Injuries Sourcebook: Basic Consumer Health Information About Sprains and Strains, Fractures, Growth Plate Injuries, Overtraining Injuries, and Injuries to the Head, Face, Shoulders, Elbows, Hands, Spinal Column, Knees, Ankles, and Feet . Health reference series. Detroit, MI: Omnigraphics; 2007: xix, 651 p.
Starkey C, Ryan JL. Evaluation of Orthopedic and Athletic Injuries . Philadelphia, PA: F.A. Davis Co; 2002: xxiv, 767 p.
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