This document summarizes a multifunctional prosthetic knee designed to allow both running and cycling with a single prosthesis. It describes how the knee uses internal mechanisms instead of bulky additions to provide stance control and flexion limiting. This allows the user to bike and run with the same prosthetic knee by disabling the damping cylinder in different modes. The prototype demonstrates that running, biking, gait assistance and stance yielding can be achieved in a single compact design. Further work is needed to develop a production-ready damping cylinder that meets the design objectives.

1. Multifunctional Prosthetic Knee
Connor Morrison, Austin Van Namen, Phil Schapiro, Matthew Hostetler, and Grant McNeill
Sponsored by Aaron Fitzsimmons, CP, OT, FAAOP
● Current prosthetic knees do not have combined
functionality for both running and cycling
● Bulky additions are often required to facilitate gait
● Lack of stance control/ yielding contributes to instability
● Users must purchase multiple prosthetics for desired
functionality
Problem Statement
Needs Assessment
Final Result
Conclusions
Acknowledgements and References
● Flexion limitation to achieve normal running gait
● Provide stance yielding
● Ability to bike and run
● All features within one prosthetic knee unit
● Must support a 225 pound person
● Minimal height, weight
Design Objectives and Components
Free Swing Mode - Biking Mode
● Allows the user to bike and run with the same prosthetic
knee by easily disabling the damping that is usually
provided by the cylinder
● Curved slot allows top link of knee to
shift without disabling polycentric
locking
● Allows up to 10 degrees of yielding
● Cantilever spring prevents unwanted
yielding during running and walking
● Cantilever allows for smooth stance
yielding
● Replaces external bulky additions via an internal stopping
mechanism
● Flexion angle limited by capping stroke length of piston
● Minimizes user’s required hip torsion
● Removable and customizable to allow for various
maximum flexion angles
Current active amputees cannot
engage in the physically athletic
lifestyles they enjoy. Aaron Fitzsimmons,
a prosthetist with The Surgical Clinic,
PLLC in Nashville, TN hopes to provide
his patients with a single product that
better suits their needs.
Step 1:
● Flip Lock
Prevention
Latch to engage
● Lock via hex key
Step 2:
● Bend knee at
90°
● Secure piston
with clasp
Step 3:
● Remove piston via
hex key
● Disengage cylinder
throughout cycle
This prosthetic knee is a proof of concept showing that
each function (biking, running, gait assistance, and stance
yielding) can be performed by one knee without mutual
exclusivity. The production is contingent upon the ability of
a manufacturer to fabricate a cylinder that would provide the
desired damping and fit within the knee’s scalable frame.
A final working design utilizing existing cylinder
technology would completely satisfy the stated needs
assessment while eliminating many existing problems for
transfemoral amputees.
Vanderbilt University School of Engineering, Vanderbilt Biomedical
Engineering Department, Dr. Matthew Walker III, Ph.D., Aaron
Fitzsimmons, CP, OT, FAAOP, The Surgical Clinic, PLLC, John
Fellenstein with the Vanderbilt Physics & Astronomy Department
Machine Shop, Brandon Burke, B.E.H.O.P.E. Peer Senior Design
Group
Final knee is a prototype of a knee prosthesis. The frame
is machined from aluminum, and the cylinder, piston, and
iGAB are 3D printed. This shows that each of these
functions can successfully work in one design.
Figure 1: Image of a
transfemoral
amputation (left) and
location of a typical
prosthesis (right).
Figure 4: Lock
Prevention Latch
(green) prevents
polycentric locking.
Figure 5: The piston
remains depressed via
the clasp (blue).
Figure 6: Removing
the Piston Connection
Pin (orange) allows
free swing.
Figure 3: Cut-away
view of the proximal
connection piece.
Cantilever in green
and pin in blue.
Stance Yielding Mechanism - (Stability Assistance)
Internal Gait Assistance Bumper - Running Mode
Example Load Analysis
Figure 2: Internal Gait Assistance Bumper (blue) is shown
above. Arrow designates relative placement while in running
mode. The tracking system (green) keeps it in place.
Design Objectives and Components
Figure 9: Final knee bent at
45° (left). Dimensioned
drawings of the final design,
all lengths in mm (above).
Side view of full
transfemoral prosthesis,
including knee (right).
Figure 7: Diagram of forces
exerted on one knee piece,
used in finite element stress
analysis (FEA).
Figure 8: FEA of top piece of
knee. Legend gives values of
maximum stress in MPa.
30
3434
58
160.7
80