A 14-year-old boy comes to the office with his mother due to progressive anterior knee pain affecting the left leg for the past 2 months. The pain started as a mild ache toward the end of a hiking trip. The patient reports no fever, night sweats, or trauma to the knee. On physical examination, he has a normal gait. The hips, knees, and ankles have full range of motion. An area of mild swelling tender to palpation is located about 3 cm below the inferior border of the patella. An x-ray of the left knee is shown in the exhibit. Overuse of which of the following muscles most likely contributed to this patient's condition?
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This patient has Osgood-Schlatter disease (OSD), a common cause of knee pain in adolescents due to overuse of the quadriceps muscle group (ie, rectus femoris, vastus intermedius, vastus lateralis, vastus medialis). The quadriceps is located in the anterior thigh and is responsible for knee extension. Its tendon initially inserts at the superior pole of the patella. The tendon envelops the patella and continues as the patellar ligament, which then inserts at the tibial tubercle. As a result, contraction of the quadriceps (eg, hiking, running) creates traction on the tibial tubercle.
In skeletally immature children, the tibial tubercle forms as a secondary ossification center (apophysis) of the tibia, and the cartilaginous nature of the developing tibial tuberosity makes it more prone to injury compared to fully ossified bone in adults. Repetitive quadriceps contraction results in chronic avulsion/fragmentation of the tubercle, with corresponding tenderness and swelling, as seen in this patient.
(Choice A) The biceps femoris, along with the semitendinosus and semimembranosus, forms the hamstring muscle group in the posterior thigh; it is responsible for hip extension and knee flexion. The long head of the biceps femoris originates from the ischial tuberosity, whereas the short head originates from the inferior third of the linea aspera. Both insert at the head of the fibula.
(Choice B) The popliteus originates from the lateral condyle of the femur and lateral meniscus and inserts at the proximal shaft of the tibia. It flexes and medially rotates the leg (unlocks an extended knee).
(Choice D) The sartorius originates from the anterior superior iliac spine and inserts at the superomedial surface of the tibia. Because of its oblique orientation across the anterior thigh, the sartorius is responsible for hip flexion, external rotation, and abduction, as well as knee flexion. This combination of movements is needed to sit in a cross-legged position.
(Choice E) The tibialis anterior originates from the lateral condyle of the tibia, the upper half of the lateral tibia, and the interosseus membrane. It inserts at the cuneiform and first metatarsal. It is responsible for ankle dorsiflexion and foot inversion.
Educational objective:
Repetitive traction at the tibial tubercle due to quadriceps contraction can lead to avulsion and fragmentation of the tibial tubercle in skeletally immature children, causing Osgood-Schlatter disease.