Suitable for outdoor use
Activity Level 2
AvalonK2VAC combines the award winning AvalonK2 biomimetic hydraulic ankle with an integrated elevated vacuum system. This combination offers K2 users a unique product that both improves safety and long term health, and increases the feeling of socket security.

Key Features

  • The benefits of the Biomimetic Hydraulic Technology together with integrated elevated vacuum
  • Walking motion generates a natural vacuum
  • No power required, quiet gentle operation
  • Residual limb volume is more stable resulting in reduced relative movement, improved socket connection, improved ground clearance and improved proprioception
  • When used in conjunction with a Silcare Breathe liner, the vacuum is applied directly to the residual limb to further enhance the connection between the limb and the socket.
  • Foot Shell and Glide Sock included.


Avalon Unique Design

The Avalon range enhances walking confidence by hydraulically adjusting to inclines and self-aligning to secure the knee joint, to encourage good posture and joint position. This improves stability, helping to prevent falls and increases balanced limb loading to provide the best performance for limited community ambulators.

The main driving force behind advancing lower limb prosthetic technology in the 21st century is biomimetic design; reproducing the biomechanical performance of natural limbs. Inherent in this is recognising that different demographics of the amputee population have different biomechanical requirements, and that the engineering principles behind different devices must accommodate for this.

With over 130 years of innovation and expertise in lower limb prosthetic technology our award-winning prosthetic products are designed with the patient in mind.

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The Benefits of AvalonK2

Hydraulic ankles help align the body interface with the ground interface, allowing for more natural movement and posture. By continuously adjusting to absorb energy, our hydraulic ankles allow for an efficient roll-over, remaining in a dorsiflexed position, increasing clearance to help reduce the risk of falls. This technology has been proven to provide a number of benefits to limited community ambulators optimising posture and comfort.

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AvalonK2VAC offers a range of motion of 6˚ plantar and 3˚ dorsiflexion with independent hydraulic adjustment. This function allows the fine tuning of the hydraulics. The improved socket connection created by the elevated vacuum compensates for the slight reduction in motion range as the better connection improves ground clearance and reduces interface pressures, this combination delivers benefits for the higher K2 level user.

AvalonK2 Purpose Designed Keel

Limited community ambulators tend to walk more slowly, with a shorter step and stride length. Providing a foot keel that is designed to accommodate natural changes in gait can provide a smoother rollover for such users. The optimised keel shape of the Avalon range considers such requirements and encourages a consistent, stable, and comfortable rollover so the user can walk more easily and move around confidently.

AvalonK2 Elevated Vacuum

AvalonK2VAC features integrated elevated vacuum, increasing stability and preserving skin health. The vacuum system creates a more secure socket connection resulting in minimized pistoning, improved symmetry of gait patterns and enhanced proprioception, all improving stability and confidence of the user.

To preserve skin health the elevated vacuum draws blood into the residual limb, providing better circulation. The elevated vacuum improves tissue oxygenation during walking and compared to other prosthetic suspension methods, decreases trans-epidermal water loss and attenuated reactive hyperaemia. A study carried out suggested that decreasing trans-epidermal water loss preserves the skin barrier function, which protects against ulcer formation.

The Silcare Breathe liner is highly recommended for use with AvalonK2VAC. Its unique design transmits moisture away from the skin to ensure a comfortable, cool and secure fit.

Scientifically Proven


Download the AvalonK2 Whitepaper

White Paper: A Study of AvalonK2

To take a more in-depth look into the Avalon range, discover our White Paper ‘A Study of AvalonK2’ where the biomechanics of the limited community ambulators gait are considered along with the latest clinical evidence for biomimetic hydraulic technology. Then uncover how the biomechanical performance of AvalonK2 can improve mobility and independence.

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Download the AvalonK2 Whitepaper

White Paper: A Study of Residual Limb Health

While prosthetic technology edges ever closer to restoring natural performance, there is also a more basic consideration – the residuum-socket interface. Even with the world’s most advanced prosthetic limb, if it is not comfortable to wear and walk with, amputees will not use it. Socket fit and comfort are inextricably linked to residual limb health, making this a critical element in achieving and maintaining a successful prosthetic prescription.

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Download the AvalonK2 Whitepaper

White Paper: A Study of Hydraulic Ankles

Over a decade after challenging conventional wisdom, new scientific evidence continues to be published on the medical advantages of hydraulic ankles. Discover our White Paper ‘A Study of Hydraulic Ankles’. 

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Clinical Compendium

Clinical Compendium

Blatchford Biomimetic Hydraulic Technology mimics the dynamic and adaptive qualities of muscle actuation to encourage more natural gait. Multiple independent scientific studies, comparing Blatchford hydraulic ankle-feet to non-hydraulic feet, have shown:

  • Greater comfort, reduced socket pressures
  • Improved safety, reduced risk of trips and falls
  • Smoother, easier and more natural gait
  • More evenly balanced inter-limb loading
  • Greater satisfaction
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This product is only available in the US and Canada.

AvalonK2VAC Clinical Evidence Reference

Improvements in Clinical Outcomes using Avalon compared to non-hydraulic feet

  • Improved gait performance
    • Faster self-selected walking speed1
    • Smoother centre-of-pressure progression1
  • Keel and ankle designed for Activities of Daily Living
    • Easier sit-to-stand2
  • Mean 34% reduction in stance phase timing asymmetry3
  • Maximum 86% reduction in stance phase timing asymmetry3
  • More symmetrical inter-limb loading1
  • Patient reported outcome measures indicate improvements
    • Mean improvement across all Prosthesis Evaluation Questionnaire domains4

Improvements in Clinical Outcomes using EVS compared to other suspension types

  • Fewer falls and less chance of multiple falls
    • No trans-tibial EVS users reported multiple falls, while 75% of the non-EVS users did5
  • Better balance in functional clinical tests
    • Significant improvements in the Berg Balance Scale (BBS), the Four Square Step Test (FSST) and the Timed-Up-and-Go (TUG) test6
  • Better balance reported in patient-reported outcome measures
    • Improvements in the Activity Balance Confidence (ABC) scale questionnaire7
  • Fewer gait compensations8-10
  • Knee contact forces not significantly different to those of able-bodied controls11
  • Decreased pistoning
    • Reductions of over 69% and 83%, compared to suction10,12 and pin-lock13 suspensions, respectively, with other researchers and practitioners reporting similar observations7,8,14,15
  • Maintain residual limb volume
    • Suction suspension = mean 6.5% loss in volume; EVS = mean 3.7% increase in volume (N.B. it is possible that the increase may have been due to the fact that these individuals attended the clinic wearing their regular prostheses before using the EVS system).10
    • Other studies have since confirmed the observation that residuum volume loss is prevented by EVS8,16-19
  • Healthier residual limb tissue and skin
    • Higher trans-cutaneous oxygen measurement after activity20
    • Decreased trans-epidermal water loss after activity20
    • Decreased attenuated reactive hyperemia20
  • Reduced interface pressures
    • Pressures reduced by a mean of 4% compared to suction suspension21
    • Pressure impulses reduced by a mean of 7.5% compared to suction suspension21
  • Improved wound management
    • Continued prosthesis use while the wounds healed22-24
    • Wounds heal more quickly with EVS than other suspension methods25
  • Less painful than other suspension methods
    • Expert opinion8 and clinical case studies26 agree that EVS is less painful and more comfortable than other suspension methods.
    • Improved Socket Comfort Score compared to other suspension methods5
  • Patients are more satisfied wearing their prosthesis5,7,8,15,23,26-28

Clinical Outcomes using the Avalon/Navigator keel design

  • Shorter keel allows for more consistent rollover radius of curvature, regardless of changing footwear29
  • The most energy efficient radius of curvature for a rollover shape has been identified as 30% of the walker’s leg length. For a person of a typical adult height between 1.5m and 1.8m, this equates to approximately 245-290mm. The Avalon keel design has a rollover shape of ~250mm29.

Other Evidence

Vacuum levels generated:

When sensory control of the lower limb joints is lost, it is essential that the replacement behaves predictably. Consistency of performance is vital in providing prosthetic confidence. In terms of socket suspension method, this means providing the same good connection throughout a gait cycle, from one step to the next, and day-to-day, over the lifetime of the socket.

The difference between the vacuum levels generated by suction suspension, and that generated when using EVS, can be demonstrated by using a negative pressure gauge30. Figure 1 illustrates these measurements. Commonly, when the user bears weight on their prosthesis during stance phase, with suction suspension, the magnitude of the vacuum is low. When the leg is lifted into swing phase, the vacuum increases in magnitude, holding the socket to the residual limb. Comparatively, EVS retains a high level during stance phase – higher, in fact, than the peak swing phase vacuum with suction. Additionally, the difference between stance and swing phase is less pronounced, so that the vacuum level is more consistent throughout the gait cycle. For the amputee illustrated in the graph30, EVS gave an approximate 85% increase in peak vacuum magnitude and an approximate 67% reduction in the ‘amplitude’ of the vacuum measurement signal.

Figure 1: Negative pressure within the socket when walking using a one-way valve suction suspension (grey) and an elevated vacuum (EV) suspension. N.B. Data recorded with Echelon Vac system.

The difference in vacuum generated by the AvalonVAC, compared to that generated by the Echelon Vac, is shown in Figure 2. Despite differences in the method used (keel vs springs, different socket, different pressure gauge), when the same patient was asked to walk at ‘K2 walking speed’ (~2km/h, short steps), the trend of vacuum level to number of steps taken was comparable to when measured at ‘K3 walking speed’ (4-5km/h) with Echelon Vac.

Figure 2: Comparison of the EchelonVAC and AvalonVAC vacuum generation by number of steps (regardless of walking speed).


1. Barnett CT, Brown OH, Bisele M, et al. Individuals with Unilateral Transtibial Amputation and Lower Activity Levels Walk More Quickly when Using a Hydraulically Articulating Versus Rigidly Attached Prosthetic Ankle-Foot Device. JPO J Prosthet Orthot 2018; 30: 158–64.
2. McGrath M, Moser D, Baier A. Anforderungen an eine geeignete Prosthesentechnologie für ältere, dysvaskuläre Amputierte - Requirements of a suitable prosthesis technology for elderly, dysvascular amputees. Orthop-Tech; 11. Download
3. Moore R. Effect on Stance Phase Timing Asymmetry in Individuals with Amputation Using Hydraulic Ankle Units. JPO J Prosthet Orthot 2016; 28: 44–48. Download
4. Moore R. Patient Evaluation of a Novel Prosthetic Foot with Hydraulic Ankle Aimed at Persons with Amputation with Lower Activity Levels. JPO J Prosthet Orthot 2017; 29: 44–47. Download
5. Rosenblatt NJ, Ehrhardt T, Fergus R, et al. Effects of Vacuum-Assisted Socket Suspension on Energetic Costs of Walking, Functional Mobility, and Prosthesis-Related Quality of Life. JPO J Prosthet Orthot 2017; 29: 65–72.
6. Samitier CB, Guirao L, Costea M, et al. The benefits of using a vacuum-assisted socket system to improve balance and gait in elderly transtibial amputees. Prosthet Orthot Int 2016; 40: 83–88.
7. Ferraro C. Outcomes study of transtibial amputees using elevated vacuum suspension in comparison with pin suspension. JPO J Prosthet Orthot 2011; 23: 78–81.
8. Gholizadeh H, Lemaire ED, Eshraghi A. The evidence-base for elevated vacuum in lower limb prosthetics: Literature review and professional feedback. Clin Biomech 2016; 37: 108–116.
9. Xu H, Greenland K, Bloswick D, et al. Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension. Clin Biomech Bristol Avon 2017; 43: 95–101.
10. Board WJ, Street GM, Caspers C. A comparison of trans-tibial amputee suction and vacuum socket conditions. Prosthet Orthot Int 2001; 25: 202–209.
11. Xu H, Greenland K, Bloswick D, et al. Vacuum level effects on knee contact force for unilateral transtibial amputees with elevated vacuum suspension. J Biomech 2017; 57: 110–116.
12. Gerschutz MJ, Hayne ML, Colvin JM, et al. Dynamic Effectiveness Evaluation of Elevated Vacuum Suspension. JPO J Prosthet Orthot 2015; 27: 161–165.
13. Klute GK, Berge JS, Biggs W, et al. Vacuum-assisted socket suspension compared with pin suspension for lower extremity amputees: effect on fit, activity, and limb volume. Arch Phys Med Rehabil 2011; 92: 1570–1575.
14. Darter BJ, Sinitski K, Wilken JM. Axial bone-socket displacement for persons with a traumatic transtibial amputation: The effect of elevated vacuum suspension at progressive body-weight loads. Prosthet Orthot Int 2016; 40: 552–557.
15. Scott H, Hughes J. Investigating The Use Of Elevated Vacuum Suspension On The Adult PFFD Patient: A Case Study. ACPOC 2013; 19: 7–12.
16. Youngblood RT, Brzostowski JT, Hafner BJ, et al. Effectiveness of elevated vacuum and suction prosthetic suspension systems in managing daily residual limb fluid volume change in people with transtibial amputation. Prosthet Orthot Int 2020; Online first.
17. Sanders JE, Harrison DS, Myers TR, et al. Effects of elevated vacuum on in-socket residual limb fluid volume: Case study results using bioimpedance analysis. J Rehabil Res Dev 2011; 48: 1231.
18. Street G. Vacuum suspension and its effects on the limb. Orthopadie Tech 2006; 4: 1–7.
19. Goswami J, Lynn R, Street G, et al. Walking in a vacuum-assisted socket shifts the stump fluid balance. Prosthet Orthot Int 2003; 27: 107–113.
20. Rink C, Wernke MM, Powell HM, et al. Elevated vacuum suspension preserves residual-limb skin health in people with lower-limb amputation: Randomized clinical trial. J Rehabil Res Dev 2016; 53: 1121–1132.
21. Beil TL, Street GM, Covey SJ. Interface pressures during ambulation using suction and vacuum-assisted prosthetic sockets. J Rehabil Res Dev 2002; 39: 693.
22. Hoskins RD, Sutton EE, Kinor D, et al. Using vacuum-assisted suspension to manage residual limb wounds in persons with transtibial amputation: a case series. Prosthet Orthot Int 2014; 38: 68–74.
23. Traballesi M, Delussu AS, Fusco A, et al. Residual limb wounds or ulcers heal in transtibial amputees using an active suction socket system. A randomized controlled study. Eur J Phys Rehabil Med 2012; 48: 613–23.
24. Traballesi M, Averna T, Delussu AS, et al. Trans-tibial prosthesization in large area of residual limb wound: Is it possible? A case report. Disabil Rehabil Assist Technol 2009; 4: 373–375.
25. Brunelli S, Averna T, Delusso M, et al. Vacuum assisted socket system in transtibial amputees: Clinical report. Orthop-Tech Q Engl Ed; 2.
26. Arndt B, Caldwell R, Fatone S. Use of a partial foot prosthesis with vacuum-assisted suspension: A case study. JPO J Prosthet Orthot 2011; 23: 82–88.
27. Carvalho JA, Mongon MD, Belangero WD, et al. A case series featuring extremely short below-knee stumps. Prosthet Orthot Int 2012; 36: 236–238.
28. Sutton E, Hoskins R, Fosnight T. Using elevated vacuum to improve functional outcomes: A case report. JPO J Prosthet Orthot 2011; 23: 184–189.
29. Curtze C, Hof AL, van Keeken HG, et al. Comparative roll-over analysis of prosthetic feet. J Biomech 2009; 42: 1746–1753.
30. McGrath M, Laszczak P, McCarthy J, et al. The biomechanical effects on gait of elevated vacuum suspension compared to suction suspension. Cape Town, South Africa, 2017.

See all the Clinical Evidence for every Blatchford product in our Clinical Evidence Finder Tool.

AvalonK2VAC Technical Data

Max. User Weight:


Activity Level:


Size Range:


Component Weight:

1lb 5oz

Build Height:


Heel Height:


†Component weight shown is for a size 26cm without foot shell.


Alignment Wedge 940093


  Size Side

For dark tone add suffix D. 
Foot example: AvalonK2 size 25 left.