A healthy 11-year-old boy complains of a “bump below his kneecap” that hurts to touch and whenhe jumps. He first felt slight pain a month earlier. Since then, he has occasionally complained ofpain and a bump on the right knee.
Case 1:Chronic Knee Pain and Swelling in a Young Basketball PlayerPATIENT PROFILE: A healthy 11-year-old boy complains of a "bump below his kneecap" that hurts to touch and when he jumps. He first felt slight pain a month earlier. Since then, he has occasionally complained of pain and a bump on the right knee. The patient usually plays basketball every day after school and on weekends. When he plays less frequently, the pain diminishes. It worsens when he plays and particularly when he falls on his knee. One day earlier, when he fell and landed on his knee, the pain increased markedly. His mother decided to seek medical attention; she was concerned that the bump might be a tumor. Examination reveals tenderness and swelling over the tibial tubercle on the right knee. Flexion in the knee is limited to 120 degrees-whereas flexion in the left knee is 150 degrees. Kneeling and squatting increase the pain. No ligamentous laxity of the knee is evident when either varus or valgus stress is applied. The patient is able to extend the right leg against resistance, although this movement does cause some discomfort. DIFFERENTIAL DIAGNOSIS OF KNEE PROBLEMS IN YOUNG ATHLETES Knee pain caused by trauma from a fall or twisting injury or overuse is a frequent complaint in young patients like this boy. The differential diagnosis includes:
All these conditions can cause swelling and tenderness in one knee that are exacerbated by activity and relieved by rest. Because the ligaments and menisci are usually stronger than bone during skeletal immaturity, injuries of these structures are rare at this phase of development. Physeal fractures are the most common type of fracture in skeletally immature athletes. In children, the physis is the weakest part of bone. Thus, injuries that would typically produce damage to the medial collateral ligament in a skeletally mature athlete will result in a physeal fracture in a less skeletally mature boy or girl. A history of recent trauma and inability to bear weight would make a fracture likely. In this patient’s case, the lack of such a history and the ability to bear weight on the painful knee make a growth plate fracture unlikely. The symptoms and history seen here are most congruent with Osgood-Schlatter disease (OSD), a type of traction apophysitis injury. Apophysitis occurs at sites where a tendon attaches to bone. OSD involves the insertion site of the patellar tendon into the tibial tubercle. Repeated strong contractions of the quadriceps muscle- such as occur in basketball, volleyball, and gymnastics- cause small evulsions of the developing tibial tubercle (
). These osseous fragments result in pain, swelling, and the formation of a tender prominence below the knee. The presence of a bump over the tibial tubercle- as in this boy-is a clue to the diagnosis. OSD occurs in patients who are between 11 and 17 years of age. The condition was once seen exclusively in boys, but now that more girls are involved in sports, it is seen in children of both sexes. It does not appear to be familial. Another type of traction knee injury, Sinding-Larsen- Johansson syndrome, is also seen in young athletes. The syndrome involves a process similar to that of OSD but at the inferior pole of the patella instead of at the tibial tubercle. It can be differentiated from OSD by the location of pain and tenderness (at the inferior edge of the patella) and by the absence of a "bump" below the knee.
WHAT WOULD YOU DO NOW?
Order an MRI scan of the knee.
Order an ultrasound scan of the knee.
Order conventional radiographs of the knee.
None of the above.
THE CONSULTANT’S CHOICE
OSD can usually be diagnosed on the basis of the typical history and physical findings (
). Although imaging studies can help confirm the diagnosis, they are not required. If plain radiographs are ordered, they typically reveal varying degrees of ossification of the tibial tubercle. Some degree of separation of the apophysis or fragmentation of a portion of the tibial tubercle may also be present (see
[radiograph inset]). If a physeal fracture of the knee were strongly suspected, it would be important to obtain a plain radiograph (choice C) while valgus stress was applied to the knee. Only radiographic evidence can distinguish between a physeal fracture and a medial collateral ligament tear (less common in a skeletally immature patient such as this boy-but still possible); both are characterized by pain and tenderness that localize to the distal femur and by weakness or opening of the knee joint when valgus stress is applied. However, neither weakness nor joint line separation was observed when valgus stress was applied to this boy's knee. Other, more costly imaging studies, such as MRI (choice A) and ultrasonography (choice B), are not usually indicated unless a complete separation of tendon from bone-or another problem, such as a tumor-is suspected. Complete separation of the tendon from the bone rarely occurs in OSD. However, if you do suspect it, see if the patient can extend his or her lower leg against resistance. Inability to do so indicates a tendon rupture, which must be confirmed by MRI or another study. This patient was able to extend his leg against resistance.
WHAT WOULD YOU DO NOW?
Reassure the family and treat conservatively.
Advise the patient not to play basketball for 6 to 12 months.
Prescribe cast immobilization and corticosteroid injection.
Refer the patient to an orthopedic surgeon for possible surgery.
THE CONSULTANT’S CHOICE
For most patients with OSD, minimal treatment (
) is appropriate; cessation of athletic activity (choice B) is not necessary. Immobilization (choice C) is very rarely indicated, and injection of corticosteroids (choice C) into the tibial tubercle is strongly discouraged. Suggest topical ice massage over the tibial tubercle to help alleviate pain and swelling. Recommend use of a pad (such as those used by skateboarders and in-line skaters) on the symptomatic knee to protect it during play. Teach patients how to perform exercises that will stretch and strengthen both the hamstring and quadriceps muscles. Prescribe NSAIDs for a minimum of 5 to 7 days (but no longer than 10 days). Finally, reassure both patients and parents that the condition will resolve as the skeleton matures. It may take 12 to 18 months for symptoms to subside completely. A residual lump may persist into adulthood, but it is usually of no significance. Surgery (choice D) is rarely needed in OSD. However, if a patient complains of severe pain and immediate swelling following a vigorous athletic maneuver, has difficulty in walking, and holds the affected leg at 30 to 40 degrees of flexion and cannot extend it against resistance, suspect acute tibial tubercle avulsion and consult an orthopedic surgeon. Nondisplaced tibial tubercle avulsions are usually treated with cast immobilization; those that are displaced, with open reduction and internal fixation.
FOR MORE INFORMATION: