chapter 3: History and Physical Examination
Patients may complain of anterior knee pain and/or patellar instability. Pain related to extensor mechanism (patellofemoral) problems typically is exacerbated by climbing or descending stairs as well as other activities that require strong quadriceps contraction. Descending stairs, which requires a coordinated eccentric contraction to lower one's body weight to the next stair, is particularly painful for many patients with patellofemoral disorders and quadriceps insufficiency. Stair climbing requires more concentric quadriceps contraction to provide knee extension lifting the body up and forward. Strenuous eccentric or concentric extensor mechanism challenge can produce musculotendinous overload and pain in an otherwise "normal" knee if adequate flexibility and strength are not present.
Prolonged periods of knee flexion such as long car rides or watching a movie can also cause pain in the anterior knee area. The reason prolonged flexion causes pain is uncertain but may be related to additional tension in sensitive peripatellar soft tissues and onto deficient patellofemoral cartilage when the knee is held in flexion. As the knee flexes, the iliotibial band is drawn posteriorly by normal tibial rollback and its strong connections to the patella exert lateral and posterior force on the lateral patellar border. Such pain is typically relieved if the patient can rest the knee in a more extended position.
Only when there is a history of documented patellar dislocation or when the patient clearly describes the patella shifting during activity should the examiner suspect that patellar instability is present. The ubiquitous "giving way" that patients describe should not be automatically considered a symptom of instability because it is often due to quadriceps insufficiency alone. Such weakness may result from long‑term deconditioning or muscular inhibition secondary to pain or effusion (l, 2). Because the vastus medialis has a lower threshold for inhibition than the rest of the quadriceps, unbalanced quadriceps inhibition may contribute to malalignment in the presence of even a small knee effusion (3, 4).
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