Acute Onset Knee Pain • Xray of the Week
A 68 year old female presenting with acute onset knee pain following crush injury of knee. What is the diagnosis?
Figure 1. Plain radiographs of the knee AP (A), and lateral (B).
Figure 2. Plain radiographs of the knee AP (A), and lateral (B). Green arrow demonstrating the avulsion fracture fragment due to the ruptured quadriceps tendon.
Figure 3. Sagittal MRI of the knee. T1 weighted image (A) and T2 weighted image (B). Green arrow demonstrating the ruptured quadriceps tendon with discontinuity and retraction.
The quadriceps muscle group is the primary extension mechanism of the knee and consists of the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. The 4 tendons of these muscles insert onto the patella as the quadriceps tendon or sometimes referred to as the quadriceps expansion.The quadriceps tendon is composed of 3 layers:The superficial layer from the rectus femoris, the middle layer composed of the vastus lateralis and medialis, and the deeper layer from the vastus intermedius [1,2]. There is some variability on the anatomic configuration of the layers of the quadriceps tendon.The vastus medialis and vastus lateralis join the superficial and deep layers of the quadriceps tendon in varying proportions as the most common anatomic arrangement .
Quadriceps tendon injury may be secondary to repetitive microtrauma, weakening from underlying medical conditions such as gout, diabetes, collagen vascular diseases, chronic renal failure [3,4,5] or from strong deceleration injury. Additional predisposing factors include older age, obesity and steroid use .
Traumatic injuries may result in acute partial or complete tears, usually a few centimeters removed from the upper patellar pole . Complete tendon rupture is usually a clinical diagnosis with loss of extensor function [2,4] and MRI is performed more for surgical planning and confirmation of diagnosis whereas in partial tendon ruptures, MRI serves a more critical role in diagnosis . Initial evaluation with acutely injured patients tends to be with radiographs in the emergency department. Associated radiologic findings include suprapatellar mass usually composed of the retracted tendon and associated edema as well as a joint effusion [Figs.1,2] . On lateral radiographs, disruption of the normal quadriceps outline may be identified as well as a soft tissue defect superior to the patella where a corresponding palpable defect may be felt on physical examination , similar to our case above [Figs.1,2]. On MRI, partial rupture of the quadriceps tendon usually is manifested by edema and heterogeneity of the quadriceps tendon. With complete rupture of the quadriceps tendon, MRI demonstrates retraction of the torn ends, and surrounding edema, and frequently a joint effusion [Fig.3] .
Treatment needs to be prompt and will be determined by degree of injury and rupture. Partial ruptures may be treated conservatively with immobilization, however complete tendon rupture with or without associated patellar fracture need emergent orthopedic evaluation and surgery in order to regain full function and prevent retraction and fibrosis .
1. Bencardino JT, Rosenberg ZS, Brown RR, Hassankhani A, Lustrin ES, Beltran J (2000) Traumatic musculotendinous injuries of the knee: diagnosis with MR imaging. Radiographics. 20(suppl1):S103–S120.
2. Zeiss J, Saddemi SR, Ebraheim NA. MR imaging of the quadriceps tendon: normal layered configuration and its importance in cases of tendon rupture. AJR. 1992;159:1031-1034.
3. Kim, Y.H., Shafi, M., Lee, Y.S. et al. Spontaneous and simultaneous rupture of both quadriceps tendons in a patient with chronic renal failure. Knee Surg Sports Traumatol Arthrosc. 2006 Jan;14(1):55-59.
4. Nance EP Jr, Kaye JJ (1982) Injuries of the quadriceps mechanism. Radiology 142:301–307.
5. Bikkina RS, Chaljub G, Singh H, Allen SD. Magnetic resonance imaging of simultaneous bilateral quadriceps tendon rupture in a weightlifter: case report. J Trauma. 2002; 52(3):582-584.5.
Alexandra (Sasha) Roudenko, MD is originally from Siberia, Russia and grew up in New York City. After graduating magna cum laude from Barnard College - Columbia University as a chemistry major, she was invited to join the prestigious Phi Beta Kappa Society. She then received her MD degree from New York University School of Medicine. Dr. Roudenko is currently a third year radiology resident at Mount Sinai West - St. Luke's and has developed a passion for body imaging. She is particularly interested in body MRI and plans on pursuing the subspecialty throughout her career. In 2016, Dr. Roudenko was awarded a fellowship in the Introduction to Academic Radiology program at ARRS.
All posts by Sasha Roudenko, MD