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The Impact of C-Leg® on the Physical and Psychological Adjustment to Transfemoral Amputation

Bunce, Daniel J. PhD; Breakey, James W. PhD, CP

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JPO Journal of Prosthetics and Orthotics: January 2007 - Volume 19 - Issue 1 - p 7-14
doi: 10.1097/JPO.0b013e31802d41a4
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In their efforts to restore the lost function and cosmetic appearance of an amputated limb, prosthetists typically perform work that involves the selection and proper fitting of a prosthesis, as well as the training of amputees in its use and maintenance. What is usually beyond the scope of prosthetists' technical expertise is an understanding of how improvements in function and cosmetic appearance transform the everyday world of the amputee. Although literature on the psychological impact of prosthetic use is available, most, if not all, of this research is based on quantitative data obtained from questionnaires and surveys and thus fails to capture the rich, complex, and often subtle experiential world of the individual. Because the detailed, experiential reports from amputees are the primary measure of how well or poorly our rehabilitation efforts are approximating their pre-amputation condition, it is crucial that we begin supplementing traditional research with qualitative methods of inquiry and analysis. In particular, we have found that work with amputees using the C-Leg® (Otto Bock Health Care, Minneapolis, MN) benefits greatly from such qualitative data.

A patient was asked: What effect on your level and nature of concentration does the improved function of the C-Leg enable? The patient responded:

C-Leg allows me to actually have 100% attentiveness to the world around me instead of the next step I'm going to take. It's taking the blinders off from the tunnel vision and allowing you to see the whole world as it is. When wearing a mechanical leg, I didn't see the birds that just flew by, I didn't see the pups that were playing out there, I didn't see the flowers, I didn't see anything, because I was right here [pointing to leg].

When asked if, in relation to his improved function, he sensed a change in the meaning or character of his surroundings, the patient responded:

Of course there is. Objects don't look like obstacles any more, they don't look like dangers anymore; they don't look like things to be cautious of. They simply are what they are now. You know what, the pot with the plant in it is a pot with a plant in it; it's not a trip hazard. Before [pre C-Leg] I would have seen that pot and made sure that I mapped out a path and avoided that plant. This [C-Leg] allows the everyday flow. I don't have to map everything, now. I can live in real-time life now.

Clearly, such responses provide us with a wealth of insight into the experience of the amputee and thus are an instrument to gauge the nature and effectiveness of our rehabilitation efforts. Accordingly, the aim of this report is to present a selection and interpretation of the verbal descriptions we have received from patients using the C-Leg and thereby demonstrate how such first-person accounts supplement traditional, quantitative research. To do this requires some preliminary remarks on our theoretical orientation and approach.

What distinguishes our approach from more traditional discussions and characterizations of limb loss and rehabilitation is that it is grounded in a phenomenological comprehension of the body as it is directly lived and experienced. That is, we do not conceive of the body as a distinct, purely physiological, objective entity. Rather, we comprehend individuals as essentially embodied. Because this view provides the basis of our approach to limb loss and rehabilitation, we cannot expect the reader to fully grasp and appreciate our analysis of the restorative impact of the C-Leg without some explanation of what we understand embodiment to mean.


What does it mean to regard the human body as a purely physiological, objective entity? According to Merleau-Ponty,1 who has given the topic its most thorough and extensive treatment, it means: 1) the anatomization of the body into a set of component physiological systems in which each system is distinguishable from, and functions independently of, the others; 2) the body exists as essentially unrelated to other worldly objects—it can be identified and defined without reference to other objects; and 3) the body functions and behaves, and is acted upon by other objects, according to the physical (causal) laws that are postulated by the empirical sciences.1

Essentially, the body is regarded as an object, and, as such, it is to be distinguished from the “subject”: the isolated mind/consciousness has or possesses and thus utilizes a body. The body is that which mediates the contact between the mental-self and the world of objects and others. Thus, the body (more specifically, a limb) is a tool, much like any other practical implement, in the service of a self-contained, isolated mind/consciousness. An instance, among many, of this view of the body as it is found in the literature on limb loss and rehabilitation comes from Kohl,2 who characterizes the human body as follows: “The body functions itself as a tool, endowed with physical properties that permit or limit the activities each person can accomplish independently. The body is also a stimulus that causes particular responses from within the person and from other people that have been culturally sanctioned” (p 139).2


Although Merleau-Ponty acknowledged that the body-as-object is indeed one profile to my experience of my body,1 the body as first lived and experienced reveals characteristics unlike those commonly assigned to all physical objects. First, the various parts and functions of the body are not distinct, but form a unity, an implicatory structure. The structural coordination of the body is revealed in the simplest of behaviors. For example, if I am sitting at a table and reaching for a cup, all the parts and functions of my body—the movement of my hands toward it, the straightening of my upper body, the tautening of my leg muscles—are enveloped in each other. The connecting link among these movements and parts of my body is their common meaning. That is, the body's visual, tactile, and motor aspects are known to us through their functional value, yet this meaning emerges only in the global activity as a whole, as a coherent bodily bearing. Without this functional coherence of body parts, meaningful behavior would not be possible. Any attempt to isolate and sectionalize the various activities that show themselves at the bodily level will lose the signification of the action itself; it will lose sight of the implicatory structure inherent in all human behavior.

Second, the lived body is not to be distinguished from its world relations. There exists an indissoluble union between the body and the world. To say this is to characterize the body as “intentional”: it is bound up with, and directed toward, an experienced world. The body is a being that presents itself only in relation to that which is other—other people, other things, an environment. Thus, the body and world exist as a unitary phenomenon. The lived body is inconceivable without the world, without that toward which its intentions are directed. Conversely, the human world as it is experienced is inconceivable, imperceptible, and unimaginable without the lived body.3 Furthermore, to characterize the body as intentional is also to express the fact that, when in the throes of my daily dealings with the world, rarely am I explicitly aware of my body. Under normal conditions, my attention is “in the world,” directed outward to the task at hand—walking down the steps, reaching for the cup, hitting the golf ball over there. In these everyday, spontaneous moments I am my body, living my body, and, as such, my body recedes from my focal attention. “The body conceals itself precisely in the act of revealing what is Other” (p 22).4

Third, Merleau-Ponty claimed that the intentional- functional behavior that characterizes the union between body and world defies attempts to provide causal explanations for perception and action that depend upon scientifically testable claims about “external” relationships.1 That is to say, behavior is neither an “outside” action on a pre-existing world of objects, nor is it a response to environmental stimuli. The types of relationships between the body and world are not causal but intrinsic or meaningful: “My bodily behavior reveals the world to me…The perceived world is relative to my behaving intentionality. …The behaving body-which-I-am is the original locus for the appropriation of sense and meaning” (pp 20–21).5 The deceptively simple point here is that the world as I first experience it is not the impersonal, neutral world of objects and relations as described by the scientist. Rather, the meaning and appearance of the objects of my everyday world reflect my personal qualities and characteristics. That is, the world as it appears always involves a constant reference to my possibilities of active response. For example, what affords walking on, reaching, manipulating, are correlative with my bodily capacities and acquired skills. Do objects not look different to the person with an amputation and to the person with a sound body? Objects are different to them. Also, in objects I see my age, background, upbringing, gender, mood, even occupation: “We see things within their context and in connection with ourselves…we see the significance things have for us…Whatever we see, hear, taste and smell concerns foremost, directly and purely, ourselves” (pp 37–38).5 Does not Main Street look and feel different to the happy person and to the depressed person, to the elderly and to the young, to different ethnic groups, etc.? Main Street is different to them because its meaning is a function of who and how each respectively lives it. Thus, meaning emerges in and through the dialectical relation between body and world such that the world becomes my world.


We have attempted to demonstrate that the body is more than a purely physiological entity by making the distinction between the body that I have—the anatomical body—and the body that I am—my basic presence to the world. The body that I am is not an object in the sense that my parts and functions are distinct, or that I exist merely spatially side by side with other objects in the world, or even that I interact in a pre-existing, impersonal world of objects and others in a strictly causal fashion. On the contrary, the body that I am is a cohesive agency essentially involved with the world. As the subject of action, the body that I am is nothing but an open-ended activity around which my experiential world emerges and changes. In short, my body is my consciousness which makes the world—with all of its manifold meanings and characteristics—be for me.

It has been our experience, as both clinicians and researchers, that the medical field has the tendency to conceive of and treat the human body as a purely physiological, objective entity. However, as we have attempted to demonstrate, the body as first lived and experienced defies such characterization and subsequent treatment. This distinction is critical. If we underestimate what it means to be a body and thus underestimate what it means to lose a limb, we ultimately fail to fully understand and appreciate the nature and importance of prosthetic rehabilitation.


Bunce6 conducted a qualitative research project on the meaning of losing a leg. The data for his study consisted of extensive narrative reports from four male unilateral, trauma-related, lower-limb amputees and was subjected to a method of empirical phenomenological analysis. A brief presentation of selected results will enhance our awareness of how the disruptions of losing a leg are directly lived and experienced and further prepare us for a discussion on the restorative impact of the C-Leg.

Bunce began by stressing that the full significance of losing a leg would be missed if we restricted our understanding of this injury to a collection of distinct functional, cosmetic, and psychological disruptions. Although the subjects of his study reported disruptions to specific areas of their everyday lives, they each maintained that the loss of their leg precipitated a transformation in their whole way of being. Expressions such as “it's global,” “completely transformed,” and “I'm not the same person” were common, emphasizing that the loss of a leg meant a fundamental transformation of the individual's sense of self in the world.

This transformation was realized and lived along a variety of dimensions. First, having lost a leg, the once cohesive unity between body and self was profoundly disrupted. That is, with subjects' behavioral capacity severely compromised, they became explicitly aware of their bodies. However, more than simply an object of their awareness, their once naturally lived, absent body emerged as an oppositional force to their intentions, a noncompliant Other. As such, any mode of comportment, with or without a prosthesis, required vigilance, negotiation, and deliberate management. They suddenly found themselves having to plan and concentrate on every movement. As one subject reported, “Before my accident, my desires and abilities were always one and one. I was very engaged, my mind and my body were there together, they were one. Now, my body feels like a thing, something that I have that prevents me from doing what I want. So, not a day goes by that I don't have to focus on and pre-think everything that I do.”

Second, in relation to subjects' acute sense of bodily dysfunction and vulnerability, their experiential world assumed a profoundly different character. Their environment transformed from that cooperative, practical field in which they once lived, to an impersonal, unavailable, and intimidating setting. Familiar objects were no longer inconspicuous aspects of their surroundings and field of movement but came to have different meanings in relation to their physical dysfunction. Steps, for example, that were previously simply there “to be climbed” became obstructions “to be circumvented.” Their surroundings were generally imposing, replete with threatening distances, obstacles, and varying terrain. To safely be involved in the surroundings necessitated constant vigilance and deliberate management. As one subject reported, “I've definitely become more aware of what the ground or terrain is like; it will literally change the way I walk. It's from having learned that if I don't accommodate, I'm going to fall. Learning to negotiate a flight of stairs, yes, stairs really scare you. Or whether it's one of those parking cements in the parking lot, or a sprinkler head, going from hard wood to carpet, anything. Now, I have obstacles, where, before, I wouldn't think about it.”

Third, having lost a leg, subjects suffered a depreciative transformation in their relations with other persons. They generally felt displaced and devalued in relation to others. They experienced and lived their sense of separateness from others in a variety of ways. The active world assumed and enjoyed by others was relatively unavailable. Their severely diminished behavioral abilities rendered them spectators. They felt excluded from the sphere of interhuman affairs, events, and activities. Able-bodied others represented an inaccessible world and, as such, a measure of subjects' sense of worth and social standing. As one subject described: “Being an amputee created a much less fluid and awkward relationship between myself and others. In all of my interactions with others I felt less of an even balance. I'm not in time or tune with others. For example, it's awkward when I'm around others who are walking, I felt weaker, just not as much of a total being that I used to be. I felt inferior and more sensitive to being experienced as less than.”Furthermore, as disfigured and disabled, subjects were often the object of the gaze and attention of others. They found that to be one-legged meant to be conspicuous, stared at, and objectified. Subjects had to contend with and be on guard against revulsion, avoidance, oversolicitousness, and pity. They became particularly sensitive to the eyes and attention of others and felt forcibly required to attend to their appearance because the possibility of being shamed or publicly shown to be defective was constant. In all, the social domain was no longer experienced and lived as a common world of shared meanings, opportunities, and respect. It had become an inimical setting marked by vigilance and the constant struggle to maintain a sense of worth and value as persons. Accordingly, for some time subjects attempted to circumvent their diminished sense of standing in relation to others by avoiding or limiting their time in public or by concealing their disability. As one subject said, “Something that really bothered me when I lost my leg is that people do look at and treat me differently. I felt inadequate, embarrassed, substandard. And I wanted to be treated like a normal person, but they didn't treat me that way. So, for a long time, if I couldn't wear my prosthesis, I just avoided going out in public or social situations. And I wasn't reminded so much, I could kind of ignore that I was missing a leg.”

Earlier, Breakey7 conducted a quantitative study with 90 male, lower-limb, traumatic amputees and found a significant relationship between how an amputee perceives his body and psychosocial well-being, specifically in the areas of anxiety, depression, self-esteem, and life satisfaction. When the group was divided into those less concerned and those more concerned about body image, in every comparison the more concerned group had significantly different scores related to psychosocial well-being, indicating the presence of more of a problem than in the less concerned group. Filiatrault8 replicated Breakey's study, reporting higher correlations along the same parameters from a sample of 55 female, lower-limb amputees in 2000. In 2001, while instructing a C-Leg course at the Veterans Administration Hospital in Long Beach, Breakey questioned whether an improvement in technology could enhance an amputee's body experience.


Fishman9 considered successful prosthetic rehabilitation to have been achieved when prosthetic use is more automatic, when the amputee's awareness of being different or physically limited becomes less threatening, and when being an amputee causes minimal interference in activities of daily living. In addition, the potential for incorporation of the prosthesis into the new body image10,11 is a desired goal but does not occur in all amputees. Further, Malone et al.12 and Bradway et al.13 considered successful adjustment for the amputee to be the incorporation of the prosthesis into the body image and a focus on the future and not on the lost anatomy.

During ambulation with present mechanical lower limb prostheses, the wearer must control the prosthesis with its functional settings predetermined by the prosthetist. To control the prosthesis, the wearer must maintain a certain level of mental concentration, which can be distracting and fatiguing. In addition, in the case of a transfemoral amputee, the fear of the prosthetic knee buckling, with a resulting fall, can raise the level of anxiety.

At the American Academy of Orthotists and Prosthetists Microprocessor Knee Forum held at Walter Reed Army Medical Center May 21 to 22, 2003, Breakey (unpublished data) presented how amputation transforms the individual's world and results in frustrations typically expressed by amputees wearing mechanical prosthesis. These include:

  • Maintains a rigid posture and guards against a possible fall.
  • Recovers from stumbles on a regular basis and falls on occasion.
  • Thinks to some degree about every step.
  • Feels less capable in various activities of daily living.
  • Has increased safety concerns in work and social situations.
  • Is aware of the additional energy required to perform activities with its resultant fatigue.
  • Is annoyed and degraded by his/her inability to keep up with others when walking.
  • Experiences overuse of the sound limb during sitting down and when descending ramps and stairs.
  • Must compensate when descending stairs, inclines, and walking on uneven surfaces.
  • Feels discomfort and fatigue in lumbar area, in compensating joints, and soft tissue on both the prosthetic side and sound limb.

Clinically, it is generally well accepted that C-Leg lowers the level of the aforementioned frustrations. Providing the transfemoral amputee with a microprocessor-controlled knee with stance and swing control, rather than a mechanical one, should lower the level of concentration needed to control the prosthesis and enhance the wearer's confidence in maintaining knee stability. Furthermore, in addition to improving gait dynamics, the cosmesis of the gait pattern should be enhanced.

The C-Leg can be described as single-axis knee/pylon system with multiple sensors that provide data to microprocessors that respond to the patient's motion. The knee joint and sensor pylon are calibrated to work together. Input is available from a sensor in the knee and from strain gauges in the ankle sensor pylon. Housed in the carbon-fiber knee frame is a hydraulic unit, which has a valve processor that opens and closes the hydraulic unit's two valves. Driven by servomotors, the valves provide damping for knee flexion and extension during gait. The C-Leg system offers the prosthetist technology that allows him/her to adjust the parameters of the knee to accommodate an individual's stability needs and gait characteristics. Armed with a new methodology consisting of a computer with Slider software (Otto Bock), the prosthetist can make very precise adjustments to the knee.

However, all too often we limit our interest to such objective outcomes and measurements and regard an improvement in function as simply that, an improvement in function. In so doing, we fail to hear and benefit from what an improvement in function means, that is, how it is lived and experienced by the amputee. When we do listen we realize that an improvement in function is never simply that. We demonstrate that when using the C-Leg, amputees experience a significant change or retransformation in their experience of their bodies, their surroundings, and relations with others.


A study was conducted to determine if a prosthesis with a mechanical knee were replaced with one that is microprocessor- controlled, what effect, if any, would it have on the amputee's body image? Subjects were recruited with the help of Otto Bock Health Care, whose involvement in this project was limited to assistance in recruitment of participants and collection of data. Otto Bock had no input in the study's protocol, had no involvement in the data analysis and interpretation, and did not fund the study. During the 2-day C-Leg courses in which prosthetists and their patients were instructed in the function of C-Leg, patients were invited to be involved in the study. The subjects who volunteered were provided with an informed consent and were asked to fill out a survey consisting of a 20-item, Likert type, Amputee Body Image Scale7 (ABIS) and demographic data on day 1 before they were fitted with the Otto Bock C-Leg. The ABIS assesses how an amputee perceives and feels about his or her body experience. The scale addresses several different domains, including 1) body appearance; 2) body function; 3) effective distress; and, 4) behavioral avoidance in social situations. The response to each item in the ABIS ranges from 1 (none of the time) to 5 (all of the time). This scale produces scores that range from 1 to 100, with low scores indicating the relative absence of a body-image concern and higher scores indicating the presence of a more serious body-image concern. Studies have confirmed the reliability of the instrument.7,8

In a study of 56 lower-limb amputees, correlation analysis between the Multidimensional Body-Self Relations Questionnaire14 (MBSRQ) subscales and the ABIS demonstrated a significant correlation (p < 0.05) between six of the ten subscales and the ABIS.15 “The correlation between the six MBSRQ subscales and the ABIS support the validity of the ABIS as an assessment tool for those with amputations” (p 199).15

After a 6-month period of C-Leg use by the participants, Otto Bock contacted the participants' prosthetists to ask the subject to complete the survey a second time. Both pre- and postsurveys were then sent by Otto Bock to the authors for analysis.

To further our understanding and to assess the importance of the statistical data, we conducted extensive, nondirective interviews with ten men who had been using a C-Leg for at least 1 year and who formerly wore mechanical prosthesis. The subjects were recruited with the help of San Francisco-San Jose area prosthetic facilities. Their responses were analyzed to reveal the significant experiential transformations while using the C-Leg, as well as to identify the commonalities and differences among them.


Forty-two recipients of the Otto Bock C-Leg were assessed before fitting of the C-Leg and in a 6-month follow-up. ABIS was assessed for reliability and was found to exceed 0.70 (coefficient alpha). The sample was predominately transfemoral amputees (90%), with two knee disarticulations, one hip disarticulation, and one proximal femoral focal deficiency; male (81%), Caucasian (90%), and married (81%), with an average age of 45.5 years (SD = 12.5). All participants reported at least a high school education, 50% having graduated from college or having obtained a graduate degree. The majority (78%) were employed full time. Seventy-one percent had experienced some trauma that resulted in amputation. The average number of years since amputation was 19.9 (SD = 15.4), and the average number of hours per day the prosthesis was worn was 14.3 (SD = 3.4).

Paired t tests examined the before and after differences in the ABIS scores (Table 1), and body image was significantly more positive at follow-up. The effect size was large (0.92), with a statistical significance of p < 0.001. These results indicate that use of the C-Leg has a positive impact on amputee body image at a level that is both statistically significant and clinically meaningful.

Table 1:
Original and follow-up variable analysis showing a difference in the ABIS scores (n = 42) indicating body image was significantly more positive at follow-up

To determine which items on the ABIS had more of an effect on enhancing the body image score, the subject's responses before and after C-Leg use were analyzed. It was found that the questions addressing body function, affective distress, and behavioral avoidance were most strongly affected.

When we consider the verbal accounts from amputees using the C-Leg, we can appreciate how such reports further our understanding of statistical data. We asked ten patients to describe their experience with the C-Leg and found a variety of interrelated themes emerge from their responses. First, in the majority (90%) of the patients interviewed, use of the C-Leg returned a more natural, fluid comportment and sense of engagement with their surroundings. This meant that the object and oppositional character of the body was significantly reduced. With focus now directed toward their practical goals, their bodies and the details of their movements receded to the background of their awareness. This allowed the concentration and energy they otherwise devoted to walking with a mechanical prosthesis to be available for the events, activities, and persons in the world around them. After using the C-Leg, one patient had this to say: “But, when I'm on the C-Leg, I just feel more natural, my body feels mine again. It's not this thing that I have to control or manipulate. I can move about with little effort and concentration. It's like my energy and attention is freed-up now for more important things, things going on around me that I used to miss.”

Second, the majority (90%) of the patients interviewed reported that the improvement in function provided by the C-Leg meant a transformation in the meaning and character of their everyday surroundings. Objects, steps, and terrain that were previously obstacles to be negotiated or avoided, resumed, to a significant degree, their once familiar, preamputation character. Thus, far less something “to be managed,” their surroundings became the natural, available world in which to participate and enjoy. As a patient described it, “Things around me just seem less threatening. I can simply enjoy the world for what it is; it's not so much of an obstacle course anymore. It's a relief to be free again to just simply see and be in the world as others do, as I once did.”

Third, the majority (90%) of the patients interviewed reported that use of the C-Leg reduced their sense of deficiency and displacement in relation to others. By significantly enhancing their ability to walk, the C-Leg enabled patients to approach the behavioral pace and performance of able-bodied others. They felt much less “out of sync” with the flow of everyday social activity and came to further re-integrate themselves and participate in the now relatively accessible, active world of others. This returned a sense of familiarity and identification with others they otherwise did not feel when using a mechanical prosthesis. “With this [C-Leg] I'm pretty much back in tune with others,” explained another patient. “I can ambulate quite effectively on it and I don't feel so cut-off or left out of what everybody else is doing. And that's really a big thing for me, because I felt like I didn't belong or that I was substandard somehow as everyone moved about freely and around me. And that was difficult to accept, it was hard on me.”

When patients are stationary and wearing pants, the C-Leg offers little improvement on a mechanical prosthesis in its ability to conceal the missing limb. When walking, however, patients found that the more natural, fluid gait that the C-Leg enables made them far less conspicuous in the presence of others and thus less concerned about being identified and treated as disabled. Some (50%) patients found this to be true even while wearing shorts and the C-Leg was exposed. The more natural rhythm and stride translated into a sense of “wholeness” or “completeness” that remained even when they knew their condition was evident to others. Exposed or not, the C-Leg gave patients a sense of confidence in their bearing and appearance and left them more willing, even eager, to be in the world with others. This patient's comment is typical: “It's really amazing how different and less noticeable my walking is. That's made a big difference for me, especially when I'm out and about in public. Being seen as disabled was a big concern for me and with my ambulation so natural now, I feel like everyone else, normal. I fit in. The funny thing is, I feel so natural on the C-Leg that I don't even mind being in shorts. That's something I would only very rarely do before [on mechanical prosthesis].”


As we have seen, because the lived body is that whereby one's experiential world comes to be, then a disruption to the lived body, such as the loss of a leg, will mean a comprehensive transformation of one's experiential world. As Bunce's research revealed,6 the loss of a leg is a fundamental disruption that was felt and lived throughout the various dimensions of subjects' experience. To them, the loss of a leg meant, among other things, a profound transformation in their relation to their body, their physical surroundings, and relations with others. As the current results indicate, use of the C-Leg precipitated a significant reversal or retransformation of these disruptions. The object and noncompliant character of patients' bodies was reduced as they were able to less self-consciously engage their surroundings. Yet, the world to which their attention was now directed had assumed a rather different appearance. It had resumed, to a great extent, its pre-amputation character of inviting objects and possibilities of engagement. Their improved function and more natural, fluid gait also meant a re-integration and re-identification with able-bodied others. This supports the finding by Swanson et al.16 that improvements in basic function and role performance lead to higher social integration. The current qualitative results also reinforce the findings obtained from the 42-subject quantitative study, namely, that improved body function leads to a reduction in both affective distress and behavioral avoidance in C-Leg wearers. Further, it satisfies Fishman's9 criteria for successful prosthetic rehabilitation.

When we consider the dynamics of skill acquisition and incorporation, we can better understand how it is that the C-Leg affords these retransformations. When learning a new skill, one is initially focused on certain rules of performance required to successfully negotiate and complete the task. When learning to ambulate with a transfemoral mechanical prosthesis, for example, the amputee pays explicit attention to every step, holding the pelvis rigid while overexerting the hip extensors to ensure a stable knee at initial contact in stance phase. Essentially, compensations in body posture and positioning are the rule. Yet the mastery of using a C-Leg coincides with the effacement of these rules, examples, the prosthesis, and one's own embodiment. It is no longer necessary to focus on the functional dynamics of one's body. These behaviors arise without focused effort, permitting one's attention to be directed elsewhere. The term incorporation characterizes this process of skill acquisition. Derived from the Latin word corpus, or “body,” incorporation literally means to “bring within the body.” Accordingly, a skill is mastered when it, previously foreign and grasped through explicit rules or examples, comes to pervade or in-corporate one's body. As previously discussed, because disappearance lies at the center of the lived body, experiential absence accompanies the incorporation of a skill: “The unproblematic use of a skill coincides with its participation in the body's focal disappearance” (pp 31-32).4 That is, it is from the skill that I now engage the world. Furthermore, like every tool whereby a skill is employed, the C-Leg itself becomes a “means whereby” and enters into focal disappearance. The C-Leg becomes part of the from structure of one's body, an incorporated instrument into one's bodily “I can.” Thus, to incorporate a C-Leg is to “redesign one's extended body until its extremities expressly mesh with the world…[one goes] from [one's] tacit embodiment to a thematically present world. However, the world [one] discovers leads [one] to redesign the body itself” (p 34).4 As patients' skills improved, the C-Leg became, to a significant degree, an extension of them, their entrance into the world. As one patient responded, “Most of the time I don't even know it's (C-Leg) there, I don't even notice it. I'm too busy going about my business, just cruisin' along.”

Besides the C-Leg, there are other microprocessor- controlled knees currently being provided to transfemoral amputees. One might question whether the results found in this study could be extrapolated to these other knees. To address this question, the authors suggest investigations be conducted with the other microprocessor-controlled knees.

A further consideration for the reader is that all of our interviewed subjects were high functional prosthetic wearers with good to excellent biomechanical skills who wore their prosthesis during waking hours with no external assists. The C-Leg system is not a panacea for all transfemoral amputees; however, prescribed appropriately, outcomes such as those presented here can be realized.


The construction and technology of the C-Leg attempt to approximate the functional capacity and ability of a sound limb. As such, the C-Leg, far more than a mechanical prosthesis, naturally lends itself to bodily incorporation and thus focal disappearance. The C-Leg becomes an instrument that transforms the amputee's body and thus returns a sense of connectedness with the world. Indeed, patients find that their sense of self in relation to their surroundings and others transforms when using it. They feel stable, able, confident, and normal. Former interests resume and new ones develop, and patients can pursue them on an effective and consistent basis. With this comes a welcomed sense of autonomy, purpose, and a heightened resolve to maximize their opportunities and restore their lives. Thus, to characterize the C-Leg as a device that improves mobility and function as compared with a mechanical prosthesis is to misrepresent, or at least minimize, its significance. The presence of the C-Leg has the power to open up a world in which the amputee may re-establish and further develop his/her place and social standing. The results of the current work reveal the C-Leg to play a vital role in the physical and psychological adjustment to amputation and thus in the restoration of one's life.

For the prosthetist whose goal is to prosthetically rehabilitate the transfemoral amputee, the availability of a prosthetic knee with a microprocessor stance and swing phase control mechanism is significant. Being able to replace mechanical knees with microprocessor designs will aid in lowering patient frustrations and help to meet functional needs. Unlike a mechanical transfemoral prosthesis, a C-Leg can be incorporated into the body and virtually disappear, precipitating a transformation of one's bodily experience, physical surroundings, and relations with others.


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body image; C-Leg; embodiment; psychological adjustment; transfemoral amputation

© 2007 American Academy of Orthotists & Prosthetists