The Clinical Syndrome

Jumper’s knee is characterized by pain at the inferior or superior pole of the patella. It occurs in up to 20% of jumping athletes at some point in their careers. It may affect one or both knees; boys and men are affected twice as commonly as are girls and women when just one knee is involved. Jumper’s knee is usually the result of overuse or misuse of the knee joint caused by running, jumping, or overtraining on hard surfaces or direct trauma to the quadriceps or patellar tendon, such as from kicks or head butts during football or kickboxing ( Fig. 110.1 ).

Jumper’s knee—characterized by pain at the inferior or superior pole of the patella—occurs in up to 20% of jumping athletes at some point in their careers.

The quadriceps tendon is made up of fibers from the four muscles that constitute the quadriceps muscle: vastus lateralis, vastus intermedius, vastus medialis, and rectus femoris. These muscles are the primary extensors of the lower extremity at the knee. The tendons of these muscles converge and unite to form a single, exceedingly strong tendon ( Fig. 110.2 ). The patella functions as a sesamoid bone within the quadriceps tendon, with fibers of the tendon expanding around the patella and forming the medial and lateral patella retinacula, which strengthen the knee joint. The patellar tendon extends from the patella to the tibial tuberosity. Weak or poor quadriceps and hamstring muscle flexibility, congenital variants in knee anatomy (e.g., patella alta or baja), and limb length discrepancies have been implicated as risk factors for the development of jumper’s knee. Investigators have postulated that the strong eccentric contraction of the quadriceps muscle to strengthen the knee joint during landing is the inciting factor rather than the jump itself.

Sagittal view of the knee.

(From Kang HS, Ahn JM, Resnick D. MRI of the extremities: an anatomic atlas . 2nd ed. Philadelphia: Saunders; 2002:341.)

Signs and Symptoms

Patients with jumper’s knee present with pain over the superior or inferior pole (or both) of the sesamoid. Jumper’s knee can affect both the medial and lateral sides of both the quadriceps and the patellar tendons. Patients note increased pain on walking down slopes or down stairs. Activity using the knee, especially jumping, makes the pain worse, whereas rest and heat provide some relief. The pain is constant and is characterized as aching; it may interfere with sleep. On physical examination, the patient notes tenderness of the quadriceps or patellar tendon (or both), and joint effusion may be present. Active resisted extension of the knee reproduces the pain. Ballottement testing will be positive in patients suffering from jumper’s knee ( Fig. 110.3 ). Coexistent suprapatellar and infrapatellar bursitis, tendinitis, arthritis, or internal derangement of the knee may confuse the clinical picture after trauma to the knee.

Patients suffering from jumper’s knee often have large joint effusions and exhibit a positive ballottement test. To perform the ballottement test for knee effusions, the clinician has the patient extend and fully relax the knee. The clinician then grasps the affected knee just above the joint space and applies pressure to displace synovial fluid from the suprapatellar pouch into the joint, which will elevate the patella. The clinician then ballotes the patella. The test is considered positive if the patella ballots easily.

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