Review for the generalist: evaluation of anterior knee pain

Anterior knee pain (see Figure 1) is one of the most common musculoskeletal complaints seen in the pediatric population. A fairly extensive differential diagnosis exists as anterior knee pain is a fairly nonspecific phenomenon. A thorough history and physical examination with attention to anatomic location of the pain, inciting factors, relationship of associated symptoms as well as a general assessment of growth and development will aid in the evaluation and treatment of this disorder. An awareness of typical injury patterns can aid the physician in narrowing the differential diagnosis. Identification of worrisome signs and symptoms will also help in defining which cases may require further evaluation. All pediatric patients presenting with knee pain require evaluation for ipsilateral hip and lumbar spine disorders. This article will review common causes of chronic anterior knee pain in the pediatric population with a focus on patellofemoral pain. It is not meant to be an exhaustive review and will not review acute traumatic knee injuries. Lateral, medial or posterior knee pain will be covered in a subsequent article.The clinical history should include a thorough description of the pain characteristics (location, character, onset, duration, change with activity or rest, aggravating and alleviating factors, night pain); trauma (acute macrotrauma, repetitive microtrauma, recent/remote); mechanical symptoms (locking or extension block, instability, worse during or after activity); inflammatory symptoms (morning stiffness, swelling); effects of previous treatments and the current level of function of the child. Patients with overuse anterior knee pain may report a sensation of giving way or instability. This sensation is usually a pseudo-giving way due to what is coined the "quadriceps inhibitory reflex" or a neuromuscular inhibition that occurs secondary to pain, muscle weakness, patellar instability or joint instability. It is important to note that true instability