Patellofemoral Pain: An Enigma Explained by Homeostasis and Common Sense.

We present a rational, scientific, low-risk approach to patellofemoral pain (anterior knee pain) based on an understanding of tissue homeostasis. Loss of tissue homeostasis from overload and/or injury produces pain. Bone overload and synovial inflammation are common sources of such pain. Chondromalacia and malalignment are findings that almost always do not need to be "corrected" to relieve pain. Patience and persistence in nonoperative care results in consistent success. Surgery should be rare and done only after extensive nonoperative management and in the setting of clearly defined pathology. Rational surgical treatment is explained in the context of restoring tissue homeostasis to relieve pain.

How to Deal With Anterior Knee Pain in the Active Young Patient.

CONTEXT: Anterior knee pain (AKP) represents the most common reason to consult with a clinician who specializes in the knee. Despite the high incidence of the disorder, however, its etiology is still controversial. Many unnecessary surgeries that may damage the patient are done for this clinical entity. EVIDENCE ACQUISITION: A PubMed search from 1995 through June 2016. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 4. RESULTS: The etiology of AKP is multifactorial, and patients with AKP may therefore be divided into several subpopulations. The whole picture must be addressed for each patient to identify all potentially modifiable factors and to achieve better outcomes. Both pelvifemoral dysfunction and psychological factors that may affect the development and symptoms of AKP must be considered to identify therapeutic targets within the context of treatment. Patients presenting with AKP frequently respond well to load restriction that protects their knee and reduces pain during rehabilitation. Surgery should only be considered in very select cases. In a patient who has undergone previous patellar realignment surgery and experienced increased pain, iatrogenic medial patellar instability should be considered. CONCLUSIONS: The etiology of AKP is multifactorial, and several subpopulations of AKP patients exist and their treatment must be personalized. Normally, the focus is on the knee of a patient with AKP, and only that joint is examined. However, that focus can lead to overlooking other important etiological factors that may be present.

The female knee: anatomic variations and the female-specific total knee design.

UNLABELLED: The concept and need for a gender-specific or female-specific total knee prosthesis have generated interest and discussion in the orthopaedic community and the general public. This concept relies on the assumption of a need for such a design and the opinion that there are major anatomic differences between male and female knees. Most of the information regarding this subject has been disseminated through print and Internet advertisements, and through direct-to-patient television and magazine promotions. These sources and a recent article in a peer-reviewed journal, which support the need for a female-specific implant design, have proposed three gender-based anatomic differences: (1) an increased Q angle, (2) less prominence of the anterior medial and anterior lateral femoral condyles, and (3) reduced medial-lateral to anterior-posterior femoral condylar aspect ratio. We examined the peer-reviewed literature to determine whether women have had worse results than men after traditional TKAs. We found women have equal or better results than men. In addition, we reviewed the evidence presented to support these three anatomic differences. We conclude the first two proposed differences do not exist, and the third is so small that it likely has no clinical effect. LEVEL OF EVIDENCE: Level IV, systematic review. See the Guidelines for Authors for a complete description of levels of evidence.

The pathophysiology of patellofemoral pain: a tissue homeostasis perspective.

UNLABELLED: Fundamental to rational, safe, and effective treatment for any orthopaedic condition is an accurate understanding of the etiology of the symptoms. The decades-old paradigm of a pure structural and biomechanical explanation for the genesis of patellofemoral pain is giving way to one in which biologic factors are being given more consideration. It is increasingly evident that a variable mosaic of possible pathophysiologic processes, often caused by simple overload, best accounts for the etiology of patellofemoral pain in most patients. Inflamed synovial lining and fat pad tissues, retinacular neuromas, increased intraosseous pressure, and increased osseous metabolic activity of the patella all have been documented as contributing to the perception of anterior knee pain. Considered together, these processes can be characterized as loss of tissue homeostasis and can be seen as providing a new and alternative explanation for the conundrum of anterior knee pain. Certain high loading conditions of the patellofemoral joint can be of sufficient magnitude to induce the symptomatic loss of tissue homeostasis so that, once initiated, they may persist indefinitely. From this new biologic perspective, it clinically matters little what structural factors may be present in a given joint (such as chondromalacia, patellar tilt or a Q angle above a certain value) if the pain free condition of tissue homeostasis is safely achieved and maintained. LEVEL OF EVIDENCE: Level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

Soft-tissue anatomy anterior to the human patella.

BACKGROUND: The purpose of this anatomic study is to report the results of dissections of the soft-tissue structures anterior to the human patella. METHODS: Sixty-one fresh or fresh-frozen and thawed human cadaver knees were dissected for this study. Thirty-five of the knees were from men, and twenty-six were from women. The soft-tissue structures anterior to the patella were dissected layer by layer and documented photographically. RESULTS: Fifty-seven (93%) of the sixty-one knees were found to have a trilaminar arrangement of fibrous soft-tissue structures anterior to the patella from superficial to deep. Those structures included a transversely oriented fascia, an obliquely oriented aponeurosis, and the longitudinally oriented fibers of the rectus femoris tendon. Between the soft-tissue fibrous layers, there were three prepatellar spaces that can be termed bursae: a prepatellar subcutaneous bursa, a prepatellar subfascial bursa, and a prepatellar subaponeurotic bursa. Four of the sixty-one knees lacked an intermediate oblique aponeurotic layer. In none of the sixty-one knees was there a potential bursal space between the rectus femoris tendon and the anterior patellar bone. CONCLUSIONS: These anatomic findings are at variance with descriptions in standard anatomic orthopaedic texts and periodical literature, including the Nomina Anatomica. None of those texts accurately describe the presence of a prepatellar aponeurotic layer or a prepatellar subaponeurotic bursa. Also, in contradistinction to descriptions in the anatomic literature, including the Nomina Anatomica, no prepatellar subtendinous bursa was found in any of the sixty-one knees.

Functional morphologic features of the human knee: an evolutionary perspective.

The complex functional morphologic characteristics of the knee are of ancient origin. The multiple asymmetries of anatomy can be traced back more than 300 million years to the pelvic appendages of Sarcoptorigian lobe-finned fish. The knee functions as a biologic transmission with ligaments acting as sensate linkages and the menisci acting as sensate, mobile bearings. Cine-computed tomography and magnetic resonance imaging studies of intact knees from cadavers reveal a combined rolling and gliding motion, with posterior displacement of the femorotibial contact point with increasing flexion. The posterior displacement of the femorotibial contact point is greater in the lateral compartment by approximately a factor of two. The anatomy of the lateral compartment, including the inferior sloping of the posterior tibial plateau, reflects and accommodates this greater motion. This asymmetry of kinematics between the medial and lateral compartment, an established characteristic of human and many other extant mammalian knees, results in an internal rotation of the tibia relative to femur with increasing flexion. By taking into account the complexities of functional morphologic features of the knee, the design of joint replacements and bracing systems may be improved.