Osgood-Schlatter disease is one of the most common causes of knee pain in adolescent athletes. This generally benign condition should be suspected in patients who present with pain, swelling and tenderness at the anterior tibial tuberosity. Radiologic studies are helpful in ruling out tumors, cysts and infections, but physical examination remains the key to diagnosis.
Pathogenesis
Osgood and Schlatter independently described this knee condition in 1903. [1] Both investigators suggested that the underlying cause was a partial traumatic avulsion of the proximal tibial tuberosity at the insertion of the patellar tendon. Histologic studies currently support a traumatic etiology for Osgood-Schlatter disease. There is little evidence to support a previously popular theory of avascular necrosis in the ossification center of the tibial tuberosity. [2,3]
The patella is subjected to biomechanical forces resulting from its attachment to the quadriceps femoris muscle proximally and the patellar tendon distally. During periods of rapid growth, the tibial tuberosity is susceptible to strain as a result of repetitive, submaximal stress from the quadriceps muscle.
Stress from contraction of the quadriceps is transmitted through the patellar tendon onto a small portion of the partially developed tibial tuberosity. This may result in a partial avulsion fracture through the ossification center. Eventually, secondary heterotopic bone formation occurs in the tendon near its insertion, producing a visible lump. Bony fusion of the tibial metaphysis with the tuberosity generally begins at age 15 in girls and at age 17 in boys, although the avulsed segment may fail to unite with the tuberosity. [4-6]
Clinical Features
The typical patient with Osgood-Schlatter disease is a 13- or 14-year-old boy, or a skeletally equivalent ten- or 11-year-old girl, who has undergone a rapid growth spurt in the preceding year. At present, Osgood-Schlatter disease is seen more frequently in boys, because of their greater participation in sports. However, the disorder is becoming more common in girls as a result of their increased involvement in athletics.
Osgood-Schlatter disease is usually unilateral, but it is present bilaterally in approximately 30 percent of cases. The disorder is more commonly seen in sports requiring repetitive quadriceps contractions, such as football, basketball, soccer, gymnastics and ballet. Discomfort is exacerbated by running, jumping, kneeling, and ascending or descending stairs. Relief is provided by rest.
The diagnosis of Osgood-Schlatter disease is based primarily on clinical features. Pain is the most common presenting complaint. The major physical findings are visible soft tissue swelling and exquisite tenderness to direct pressure over the proximal tibial tuberosity at the site of patellar tendon insertion. A firm mass may be palpable in the involved area. The symptoms are reproducible by extending the knee against resistance, stressing the quadriceps, or by squatting with the knee in full flexion.
Since Osgood-Schlatter disease is entirely extra-articular, the knee joint examination is normal. Thus, there is no joint effusion or synovial thickening. Arthroscopy is of no value unless an intra-articular disorder is suspected. Evaluation should include anteroposterior and lateral films of the knee to rule out infectious and neoplastic processes. A number of musculoskeletal conditions also should be considered in the differential diagnosis (Table 1).
Symptoms usually disappear spontaneously within one year, although discomfort may persist for two to three years until closure of the tibial growth plate is complete in late adolescence. Recurrences are common. Persistent complaints may be secondary to residual enlargement of the tuberosity or to ossicle formation in the patellar tendon [4,5,11] (Figure 1).
Radiologic Findings
Although radiographic abnormalities are frequently found in patients with Osgood-Schlatter disease, there are no definitive radiologic criteria for the diagnosis of the condition. Some knowledge of the normal pattern of ossification of the tibial tuberosity is helpful, since irregularity of the tibial tuberosity is often noted as a normal pattern in asymptomatic growing children. Thus, only symptomatic irregularities of the tibial tuberosity indicate this disease (Figures 2 and 3). Other radiologic features commonly present in clinically symptomatic patients include thickening of the patellar tendon and soft tissue swelling anterior to the tuberosity in the acute phase (Table 2).
A lateral radiograph taken with the knee in slight internal rotation may demonstrate proximal displacement of the patella or a mobile bony fragment anterior to the tuberosity. Low-kilovoltage (kV) radiography and xeroradiography may be useful in the interpretation of subtle soft tissue changes. [4,5,10]
Treatment and Complications
Most cases of Osgood-Schlatter disease are self-limited. In mild cases, symptoms will subside with conservative treatment directed at the avoidance of physical activities requiring frequent deep knee bending for a period of two to four months. Before the resumption of normal physical activity, therapeutic exercises are initiated to strengthen the quadriceps and hamstrings. These exercises include quadriceps isometrics, straight leg raising and hamstring isotonic-resistive exercises, each conducted in three sets of ten repetitions.
When voluntary limitation of activity is unsuccessful, an alternate approach to treatment includes the use of either an infrapatellar strap [11] or a Marshall-type knee brace. [8,9] A basketball kneepad is often sufficient to reduce tension on the quadriceps muscle. If the patient remains symptomatic, a walking cylinder cast is recommended to immobilize the knee in full extension for three to six weeks. This approach may be particularly difficult, however, when the patient's symptoms are bilateral. Cast removal is followed by a knee-strengthening exercise program.
Analgesics are prescribed to control pain and reduce local inflammation. In most cases, corticosteroid injections should be avoided because of the risk of degenerative changes to the patellar tendon, subcutaneous tissue atrophy and depigmentation of the skin. [12,13]
Surgical treatment is recommended for the relief of recurrent, disabling episodes that do not respond to conservative management or for the removal of a cosmetic deformity. A variety of surgical procedures, such as simple excision of the mobile ossicle through a longitudinal incision in the patellar tendon or a tuberosity-thinning procedure followed by ossicle excision, can relieve the discomfort and disability. [14-16]
Rare complications have been reported, despite conservative or surgical treatment of Osgood-Schlatter disease. [3-5,15] These complications are listed in Table 3.
Final Comment
The family physician can diagnose and treat most patients with Osgood-Schlatter disease. Conservative treatment usually consists of avoidance of pain-producing activities (especially those involving the knee), analgesics for pain relief, pads or braces for support, and therapeutic exercises to strengthen the knee. For patients whose symptoms fail to respond to these conservative measures, referral to an orthopedic surgeon is appropriate. The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the U. S. Army or the Department of Defense.
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COPYRIGHT 1990 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group
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