Quadriceps Expansion Syndrome
The Clinical Syndrome
The quadriceps expansion syndrome is an uncommon cause of anterior knee pain encountered in clinical practice. This painful condition is characterized by pain at the superior pole of the patella. It is usually the result of overuse or misuse of the knee joint such as running marathons or direct trauma to the quadriceps tendon from a kick or head butts during football. The quadriceps tendon also is subject to acute calcific tendinitis, which may coexist with acute strain injuries. Calcific tendinitis of the quadriceps tendon has a characteristic radiographic appearance of whiskers on the anterosuperior patella.
The quadriceps tendon comprises fibers from the four muscles that comprise the quadriceps muscle: the vastus lateralis, the vastus intermedius, the vastus medialis, and the rectus femoris. Fibers of the quadriceps tendon expanding around the patella form the medial and lateral patella retinacula and help strengthen the knee joint. These fibers are termed expansions and are subject to strain, and the tendon proper is subject to the development of tendinitis.
Patients with quadriceps expansion syndrome present with pain over the superior pole of the patella, more commonly on the medial side. The patient notes increased pain on walking down slopes or down stairs. Activity involving the knee worsens the pain; rest and heat provide some relief. The pain is constant and characterized as aching; it may interfere with sleep.
What are the Symptoms of Quadriceps Expansion Syndrome
On physical examination, patients with quadriceps expansion syndrome have tenderness under the superior edge of the patella, occurring more commonly on the medial side. Active resisted extension of the knee reproduces the pain. Coexistent suprapatellar and infrapatellar bursitis, tendinitis, arthritis, or internal derangement of the knee may confuse the clinical picture after trauma to the knee joint. If the quadriceps tendon has completely ruptured, a suprapatellar defect will be noted.
How is Quadriceps Expansion Syndrome diagnosed?
Plain radiographs of the knee are indicated in all patients with quadriceps expansion syndrome pain. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated.
Magnetic resonance imaging (MRI) and ultrasound imaging of the knee is indicated if internal derangement, occult mass, or tumor is suspected. Bone scan may be useful to identify occult stress fractures involving the joint, especially if trauma has occurred.
Anterior knee pain most commonly is due to arthritis of the knee; this should be readily identifiable on plain radiographs of the knee and may coexist with quadriceps expansion syndrome. Another common cause of anterior knee pain that may mimic or coexist with quadriceps expansion syndrome is suprapatellar or prepatellar bursitis. Internal derangement of the knee or torn medial meniscus may confuse the clinical diagnosis, but should be readily identifiable on MRI of the knee.
Initial treatment of the pain and functional disability associated with quadriceps expansion syndrome should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Local application of heat and cold may be beneficial. For patients who do not respond to these treatment modalities, injection of the quadriceps expansion with a local anesthetic and steroid may be a reasonable next step.
To inject the quadriceps expansion, the patient is placed in the supine position with a rolled blanket underneath the knee to flex the joint gently. The skin overlying the medial aspect of the knee joint is prepared with antiseptic solution. A sterile syringe containing 2 mL of 0.25% preservative-free bupivacaine and 40 mg of methylprednisolone is attached to a 25-gauge, 11⁄2-inch needle using strict aseptic technique. With strict aseptic technique, the medial edge of the superior patella is identified. At this point, the needle is inserted horizontally toward the medial edge of the patella.
The needle is advanced carefully through the skin and subcutaneous tissues until it impinges on the medial edge of the patella. The needle is withdrawn slightly out of the periosteum of the patella, and the contents of the syringe are gently injected. There should be little resistance to injection. If resistance is encountered, the needle is probably in a ligament or tendon and should be advanced or withdrawn slightly until the injection proceeds without significant resistance. The needle is removed, and a sterile pressure dressing and ice pack are placed at the injection site. Ultrasound guidance may improve the accuracy of needle placement and decrease the incidence of needle-related complications.
Complications and Pitfalls
The major complication of this injection technique is infection. This complication should be exceedingly rare if strict aseptic technique is followed. Approximately 25% of patients report a transient increase in pain after injection of the quadriceps tendon of the knee, and patients should be warned of this possibility. The clinician also should identify coexistent internal derangement of the knee, primary and metastatic tumors, and infection, which, if undiagnosed, may yield disastrous results.
This injection technique is extremely effective in the treatment of pain secondary to the causes of quadriceps extension syndrome mentioned earlier.
Coexistent bursitis, tendinitis, arthritis, and internal derangement of the knee may contribute to the patient’s pain and may require additional treatment with more localized injection of a local anesthetic and depot steroid.
This technique is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. Care must be taken to use sterile technique to avoid infection and universal precautions to avoid risk to the operator. The use of physical modalities, including local heat and gentle range-of-motion exercises, should be introduced several days after the patient undergoes this injection technique for tibiofibular pain.
Vigorous exercises should be avoided because they would exacerbate the patient’s symptoms. Simple analgesics and NSAIDs may be used concurrently with this injection technique.