Scott F. Dye

The Knee as a Biologic Transmission With an Envelope of Function: A Theory

The knee can be characterized as a complex set of asymmetrical moving parts acting together as a living biologic transmission. The purpose of this system is to accept, transfer, and dissipate loads generated at the ends of the long mechanical lever arms of the femur and tibia. In this analogy, the various ligaments represent sensate adaptive linkages, the articular cartilages represent bearings, and the menisci, mobile sensate bearings within the transmission. The muscles represent both living engines providing motive forces, and brakes and dampening systems under complex neurologic control mechanisms. The range of load that can be applied across an individual joint in a given period without supraphysiologic overload or structural failure can be termed the envelope of function. This range of homeostatic loading can be graphed with increasing applied loads on the vertical axis and the frequency of loading on the horizontal axis. At least 4 categories of factors together determine the envelope of function for a given joint including anatomic, kinematic, physiologic, and treatment factors. This theory of joint function can result in a more rational clinical approach to treating patients with knee injuries and other orthopaedic conditions. Orthopaedic therapy should be designed to maximize the envelope of function of musculoskeletal systems with the least degree of risk.

The Female Knee: Anatomic Variations and the Female-specific Total Knee Design

AbstractThe 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

Patients with patellofemoral pain represent a significant challenge to the orthopaedic community. The origin of patellofemoral pain can be directly traced to supraphysiologic mechanical loading and chemical irritation of nerve endings, denoting loss of tissue homeostasis. The persistent biologic cascade of cytokine production can lower the load-acceptance capacity of soft tissues and activate painful osseous remodeling. Activities of daily living can become supraphysiologic loads to sensitized patellofemoral tissues, resulting in chronic reactivation of tissue inflammation. The principles of treatment in most patients with patellofemoral pain consist of protection of sensitive tissues from excessive loading, appropriate antiinflammatory therapy, and nonirritat-ing rehabilitation.

The mosaic of pathophysiologycausing patellofemoral pain: Therapeutic implications

Abstract Before embarking on a therapeutic program to treat patients with patellofemoral pain, including surgicalintervention, it is crucial to have an understanding of the pathophysiology causing the symptoms. Our view of the genesis of patellofemoral pain is that the loss of homeostasis of innervated patellofemoral tissues often unimagable by standard radiographic studies, including magnetic resonance imaging, is a more important factor than the presence of abnormal structural characteristics. The most likely sources of nociceptive output in patients with patellofemoral pain are the innervated peripatellar soft tissues, including synovium, and the intraosseous environment of the patella. The goal of treatment of patients with patellofemoral pain should be the restoration of tissue homeostasis rather than the achievement of a “normal” patellofemoral position. Conservative measures, including scrupulous load restriction, anti-inflammatory therapy, and rehabilitation, should be tried first in most cases. Failing an appropriate conservative therapeutic course, a cautious and analytical approach to surgical treatment may be warranted.

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.Clinical Relevance: With improved knowledge of the prepatellar soft-tissue anatomy, orthopaedic surgeons should be able to more readily identify the extant structures and to better protect and repair them during surgery. This knowledge should also assist both orthopaedic surgeons and radiologists in the interpretation of soft-tissue imaging of the knee.

Restoration of osseous homeostasis after anterior cruciate ligament reconstruction

Patients with symptomatic ACL insufficiency frequently develop regions of periarticular increased osseous metabolic activity that is detectable by technetium 99m-labeled methylene diphosphonate scintigraphy (Refs. 1, 6, 8; A. Alexander, et al., unpublished data, 1992). Over the years, we have gained experience with sequential technetium bone scans in the evaluation of patients with anterior knee pain2~5 and meniscal tears.3,4 We have found that the increased osseous metabolic activity detected by scintigraphy is often

The Future of Anterior Cruciate Ligament Restoration

Advancements in the understanding of anatomy, kinematics, and physiology should improve future treatment of anterior cruciate ligament injured knees. The ultimate goal of full restoration of an anterior cruciate ligament injured knee to preinjury status, may be possible in the distant future through genetic manipulation inducing regeneration of tissues. In the midterm future, resorbable stents with incorporated bioactive growth factors have the potential of inducing normal anterior cruciate ligament anatomy without the need for detrimental harvesting of the patients tissues, or risk of microbial transmission with the use of an allograft. In the near future, the development of more benign autografts and allografts is possible along with methods of resorbable fixation of the graft to bone. Future development of 3-dimensional arthroscopic visualization and robotic surgical techniques have the potential for improvement in graft placement. Advancements in treatment of anterior cruciate ligament deficient knees also can be expected from nonsurgical areas, such as control of muscle atrophy, enhancing cerebellar-proprioceptive rehabilitation, and better bracing techniques. The basic principle of therapy should be to maximize the functional load acceptance and transference capacity of the knee with the least degree of risk to the patient.

Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Factors Contributing to Function of the Knee Joint after Injury or Reconstruction of the Anterior Cruciate Ligament*†

Restoration of musculoskeletal function is a fundamental goal of orthopaedic treatment. Until now, clinical orthopaedic concepts of injury, repair, and restoration of function of musculoskeletal systems have been described and understood primarily in structural and biomechanical terms. This perception probably evolved because the structural characteristics are the most readily visualized factors, both in the clinical setting (for example, pathological laxity due to a ruptured ligament or a fracture) and through the preponderance of structural and pathoanatomical data offered by most current imaging modalities. Structural characteristics are also the factors most directly altered by operative intervention, such as stability following repair or reconstruction of a ligament or fixation of a fracture. It is a common belief that the restoration of measurable structural and biomechanical parameters to an injured joint, such as the knee, indicates the restoration of function to that system. We do not share this view. In the past few years, emerging clinical and basic-science findings have indicated a much greater degree of underlying biological complexity. Evidence suggests that the correction of identifiable structural abnormalities is often not sufficient to restore a joint to its full preinjury level of physiological function. For example, replacement of a ruptured anterior cruciate ligament with a graft does not necessarily prevent pain, swelling, or degenerative changes in the knee, even if the increased anterior-posterior laxity that had been present before the procedure is restored to normal. This observation indicates that factors other than anatomical and structural ones probably contribute to the restoration of joint function after injury. We believe that, although these other factors are less easily visualized, they play an important role in the ultimate functional status of an injured musculoskeletal system, such as the knee. The purpose of this Instructional Course Lecture is to discuss the concept of musculoskeletal function and to …

Patellofemoral Pain Current Concepts: An Overview

The conceptualization of factors responsible for the etiology of patellofemoral pain are changing. In the recent past, chondromalacia and malalignment were believed to be most important factors relative to the genesis of anterior knee pain symptoms. However, new evidence from Europe and North America indicates other factors may be more important, such as overuse of anatomically normal patellofemoral structures, leading to the possible loss of both osseous and soft tissue homeostasis. The range of painless loading compatible with tissue homeostasis of a joint without causing structural or physiologic injury is termed the “envelope of function.” Restoration of the envelope of function as safely and predictably as possible is viewed as the primary underlying principle of treatment for patients with patellofemoral pain.

Therapeutic Implications of a Tissue Homeostasis Approach to Patellofemoral Pain

The underlying principle of treatment for patients with patellofemoral pain from a tissue homeostasis perspective is to maximize the range of painless loading for a given symptomatic joint (envelope of function) as safely and predictably as possible. Current therapeutic approaches aimed at surgical correction of chondromalacia and malalignment often are neither safe nor predictable. A tissue homeostasis approach involves addressing the pathokinematics—primarily through temporary but scrupulous load restriction, anti-inflammatory therapy, and a gentle painless rehabilitation program. Failing this, a careful and analytical surgical approach may be warranted to include a possible gentle peripatellar synovectomy.