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As this work is published, at the beginning of the 21stCentury, a new perspective of the clas- sic orthopedic enigma of the patellofemoral pain problem is becoming increasingly accepted. It is clear that the decades-old para- digm of a pure structural and biomechanical explanation for the genesis of patellofemoral pain is inadequate, and that a new era has begun with biological factors now being given more consideration. A variable mosaic of pathophysiologic events (often due to simple overload) such as patellofemoral synovitis, reti- nacular neuromas, patellar tendonitis, and painful increased osseous remodeling of the patellofemoral joint - processes when taken together can be characterized by the term “loss of tissue homeostasis” - can be seen as provid- ing new and alternative explanations for the conundrum of anterior knee pain. It clinically matters little what structural factors may be present in a given joint (such as chondromala- cia, patellar tilt or a Q angle above a certain value) if the pain free condition of tissue home- ostasis is achieved and maintained. Despite recent conceptual advances - represented by this newer biological perspective - much remains to be discovered regarding the patellofemoral joint before it can be said to be fully understood.
Better methods of determining dynamic patellofemoral joint reaction forces and kine- matics need to be developed utilizing perhaps cine-CT or cine-MRI. Actual in vivo measure- ments are still required, particularly under real- time loading conditions to calibrate any non-invasive external assessment system that may be devised. Methods of geographically
manifesting the homeostasis characteristics of all tissues, including soft tissues, need to be developed perhaps with techniques such as fMRI or CT-PET, which could help objectively evaluate the effectiveness of a variety of current and future non-operative and operative thera- pies. I envision a day when this information may be displayed in a dynamic three-dimen- sional hologram with the structural and tissue homeostasis characteristics of the patellofemoral joint being represented by dif- ferent colors and intensities.
Before advanced imaging techniques can be properly interpreted, further work on the histopathology associated with the genesis of patellofemoral pain needs to be accomplished, such as that currently being carried out by Sanchis-Alfonso. Simple tools that may be help- ful to the clinician in assessing a joint’s degree of homeostasis, such as the accurate determina- tion of surface temperature through inexpen- sive hand held devices, could be developed and calibrated. New methods of treatment aimed at addressing the pathophysiology of loss of tissue homeostasis, that may seem unorthodox from today’s perspective, such as the use of the hor- mone calcitonin in patients with painful increased osseous metabolic activity mani- fested by an intensely positive bone scan may, in time prove useful -whereas the ill considered and indiscriminate use of the lateral retinacular release, may not.
Those of us with a specific interest in the research of the patellofemoral joint also face general problems common to all musculoskele- tal systems including discovering the factors that result in the induction, persistence, and
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eventual resolution of muscle atrophy. Subtle but important neuromuscular mechanisms such as the proprioceptive , spinal, and cerebel- lar systems that determine to a great degree the adaptive temporal sequencing of motor unit contractions, could be better understood and ultimately controlled for therapeutic benefit.
Other mysteries of the patellofemoral joint remain to be answered including, determining why some patients may indefinitely remain
asymptomatic despite obvious radiographically identifiable structural abnormalities such as advanced chondromalacia, substantial malalign- ment, and even established degenerative arthrosis. When the patellofemoral joint is eventually understood in greater depth, the insights discovered should be generally appli- cable to other sub-disciplines within the field of orthopaedic surgery and musculoskeletal medicine as well.
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