Biological Causes of Anterior Knee Pain

Abstract

We review the pathophysiology of anterior knee pain in the young patient. Emphasis is placed on newer findings. We have developed what we call the “Neural Model” as an explanation for the genesis of anterior knee pain. We have demonstrated a neuroanatomical basis for PFPS in the young patient and the clinical observation that the lateral retinaculum may have a key role in the origin of this pain. According to our studies we hypothesize that periodic short episodes of ischemia in the lateral retinaculum could be implicated in the pathogenesis of anterior knee pain, at least in a subgroup of anterior knee pain patients, by triggering neural proliferation of nociceptive axons (substance P positive nerves), mainly in a perivascular location. Our findings are compatible with the tissue homeostasis theory widely accepted currently to explain the genesis of anterior knee pain. If the “neural model” of anterior knee pain proves to have a certain validity, it would lead in many cases to therapeutic recommendations to alleviate pain more effectively and safer than the attempts to correct “malalignment.” Moreover, we believe that instability in patients with PFPS can be explained, at least in part, because of the damage of nerves of the lateral retinaculum which can be related with proprioception. Our findings, however, do not preclude the possibility of pain arising in other anatomical structures such as infrapatellar fat pad, synovium and subchondral bone.