O&P Library > Orthotics and Prosthetics > 1959, Vol 13, Num 3 > pp. 75 - 79

Study of Knee Units

William McIlmurray *
Henry Gardner *

In the December 1957 issue of the Orthopedic and Prosthetic Appliance Journal, we outlined the VA Prosthetic Center's plans to study and classify prosthetic knee units available commercially. Since that time, the following eleven (11) units have been submitted, primarily as a result of the article:

1. C.H. Davies Company-Davies Metal A/K Knee
2. Fillauer Surgical Supplies-Vari-gait-V100
3. Henzel Artificial Limb Corp.-Polymatic Knee
4. K & K Prosthetic Supplies Inc.-Adult Knee Assembly, No. 8200C
5. K & K Prosthetic Supplies Inc.-Lang Knee
6. Kingsley Manufacturing Co.-Kingsley Western Knee
7. The Knit-Rite Company-Knit-Rite Knee and Shin Assembly
8. John J. McCann Company-A/K Wood Set-Up with Aluminum Knee Control
9. Otto Bock Orthopedic Industry Inc.-Otto Bock Safety Knee
10. U.S. Manufacturing Company-A/K Knee Shin Assembly
11. U.S. Manufacturing Company-Hydra-Cadence Unit

For the first phase of the study, a catalog-type format has been developed to describe the knee units. Drafts of descriptive material and drawings of two units submitted for evaluation are presented here (Numbers 2 and 9 in above list). These drafts have been submitted to the respective suppliers for their comments and approval prior to this publication. VAPC intends to publish material such as this from time to time.

The second phase of the study will involve fittings to amputees in an attempt to determine advantages and limitations of each knee unit under actual practical conditions. Ranges of motion and the nature of swing and stance phase controls will be determined, and data from these tests will be published with the consent of the manufacturer at some future date as addenda to the first phase of the evaluation.

The functional code shown in the classification was developed jointly by the VAPC and the University of California, Berkeley and described in the report, A Functional Classification of Lower Extremity Prosthetic Components As Proposed By The VAPC & UC-B , dated October 1, 1958 by F. A. Witteck, VA Prosthetics Center. We wish to extend our thanks to Mr. A. Bennett Wilson, Secretary, OALMA Committee on Advances in Prosthetics who assisted in setting up the enclosed format.

We again urge manufacturers, wholesalers, and distributors, of A/K prosthetic knee set-ups who have not done so already to include their devices in the VAPC study by sending a sample of each device to the Chief, VA Prosthetic Center, 252 Seventh Avenue, New York 1, New York. Also any comments that will help make this type of presentation more useful to clinic teams will be appreciated.

The Vari-Gait-V100 Knee Unit

Nomenclature: Vari-Gait-V1OO Functional Code: S-4-RB-RFE
Source of Supply: Fillauer Surgical Supplies (German Import); 930 East Third Street, Chattanooga 1, Tenn.
General Description: Basically willow wood construction, 18-1/2" overall length.
Functional Description:

1. Swing Phase:
   1. Swing Control (friction): Adjustment screw E ( Fig. 1 ) forces brake shoe lining C to engage fibre braking surface B of knee. The eccentric contour of the knee provides variable mechanical friction through the swing phase.
   2. Extension Bias and Resistance to Flexion (excessive heel rise): Wire yoke (stick type) linkage engages two (2) rubber bumpers; bumper H resists excessive flexion and aids extension bias bumper G .
   3. As C.
   4. Terminal Deceleration or Impact Control: Elastic terminal deceleration strap I is attached to wire yoke F damping full knee extension. Terminal deceleration is also provided by eccentric contour of fibre braking surface B . Rubber bumper J engages metal knee stop providing a cushion against terminal impact.
2. Stance Phase:
   1. Weight Bearing Brake: Dual compression springs A permit knee assembly to drop engaging fibre braking surface of knee B with brake shoe C of shank. Brake adjustment bolt D has dual eccentric surfaces acting against compression spring A controlling space between B and C .

Description of Sub-Assemblies:

1. Knee Section:
   1. Width (Bolt): Various sizes, depending on calf measurement.
   2. Length: 5" from top to knee center.
   3. External Contour and Top Diameter: Partially shaped, top diameter 6".
   4. Internal Contour: 3" depth, 3" diameter.
   5. Bushing: Phenolic bushing (2 halves) in a two-piece plastic housing.
   6. Friction:
      1. Swing Phase: Adjustment for terminal deceleration.
      2. Stance Phase: Contoured fibre knee surface mates with balata belt brake shoe to provide weight bearing brake.
         Remarks:Three-piece laminated willow wood knee section.
2. Shank Section:
   1. Length: 14" from base to knee center.
   2. External Contour & Base Diameter: Partially shaped, 3 1/4" x 2 3/4" oval shape.
   3. Internal Contour: Hollow (finished).
      Remarks: Transverse hardwood dowel serves as platform for extension bias mechanism. Transverse metal rod serves as anchorage point for elastic strap.
3. Side Straps:
   1. Material: Flat Bar - Carbon Steel
   2. Bar Size & Shape: 5" long modified flat "T" bar.
   3. Joint Head Size: 29/32 diameter x 1/4" head.
      Remarks: Joint heads plated - Permanently attached.
4. Knee Control Assembly:
   1. Knee Bolt: Slotted carbon steel expansion bolt 5/8" o.d., external thread (for side strap). Internal thread left hand for lock screw (bolt). Internal thread for expansion cap screw (friction).
   2. Bearing and or Housing: Full plastic bearing (two-piece) with (plastic) swing lever and carbon steel bolt, mounted in phenolic hearing. Plastic axis bearing, spring loaded.
   3. Linkage Mechanisms: Plastic covered carbon steel linkage with plastic yoke to compress extension bias spring; a 3/16" carbon steel linkage (bearing) bolt is secured by two round nuts. Plastic covered carbon steel guide bolt witli>threaded end to provide spring adjustment.
   4. Elastic Resistors: Extension bias control mechanism having a com-pression spring with plastic T bar. Rubber cushion rings for plastic (axis bearing) mountings.
   5. Hydraulic: None
5. Knee Stop Control and/or Terminal Deceleration
   1. Stick: None
   2. Rubber or felt: Rubber inserts in knee and shank sections.
   3. Straps or Cord: None
   4. Metal Knee Control: None
      Remarks: Lower shank section rubber stop engages knee section rubber stop to cushion terminal impact.

Special Considerations:

1. Physical Dimensions:
   1. Supplied in rights and lefts, can be ordered in knee width size 3 1/2 in. and calf sizes 30, 32, 34, 36, 38, 40 centimeters.
   2. Components and parts are dimensioned in metric system.
2. Functional Controls:
   All controls provided are contained within the unit.
3. Adaptability:
   1. This unit can be used in conjunction with most foot-ankle units currently available.
   2. Will accommodate A/K stumps to within approximately 2" of knee center.
   3. Can be used with A/K adjustable leg and alignment duplication jig.

The Otto Bock Safety Knee Unit

Nomenclature: Otto Bock Safety Knee
Functional Code: S-4-RFB-RFE
Source of Supply: Otto Bock Orthopedic Industry, Inc. (German Import); 219 Fourteenth Ave. N., Minneapolis 11, Minn.
General Description: Basically willow wood construction, 18" overall length.
Functional Description:

1. Swing Phase:
   1. Swing Control (friction): Slotted bolt F ( Fig. 2 ) expanded in plastic knee bolt bushing by internal cap screw provieds adjustable mechanical friction which is constant through the swing phase.
   2. Extension Bias: Plastic yoke (stick type) G engages plastic spring compressor H . Compression of spring I provides extension bias.
   3. Resistance to Flexion (Excessive heel rise): Combination of paragraphs graphs a and b provide resistance to flexion.
   4. Terminal Deceleration or Impact Control: Rubber bumpers J and K provide cushion against terminal impact.
2. Stance Phase:
   1. Weight Bearing Brake: Compression of spring "A" permits knee assembly to drop, engaging braking groove B (in knee section) with braking segment C of shank. Pivot bolt D permits vertical movement of (floating) knee section; adjustment pin E governs space between B and C .

Description of Sub-Assemblies:

1. Knee Section:
   1. Width (Bolt): 3 1/2"
   2. Length: Approximately 5" from top to knee center.
   3. External Contour and Top Diameter: Partially shaped, top diameter 6".
   4. Internal Contour: 3" depth, 2 1/2" diameter.
   5. Bushing: Plastic knee bushing (2 piece).
   6. Friction:
      1. Swing Phase: Internal type of Knee Bolt Expansion.
      2. Stance Phase: Female braking groove (hardwood) mates with hardwood male member (plastic lined).
      Remarks:
2. Shank Section:
   1. Length: 13" from base to knee center.
   2. External Contour: Partially shaped, 3 l/4" x 3" oval base. Available in calf circumference of 30, 32, 34, 36, 38, 40 centimeters.
   3. Internal Contour: Hollow (finished).
      Remarks: Male component of hardwood braking segment engages with female component of knee segment to provide weight bearing brake.
3. Side Straps:
   1. Material: Flat Bar - Carbon Steel
   2. Bar Size & Shape: 5" long modified "T" bar.
   3. Joint Head Size: 31/32" o.d., 7/32" thick.
      Remarks: Joint heads plated - Permanently attached.
4. Knee Control Assembly:
   1. Knee Bolt: Carbon steel, hollow bolt, 5/8" o.d., external thread on medial side, internal thread on lateral side for lock screw.
   2. Bearing and or Housing: Two section plastic knee bolt bearings ( floating, spring loaded) functioning within two-piece plastic bushings.
   3. Linkage Mechanisms: Carbon steel 5 32" o.d. wire frame forms two guide rod ends. Two rubber bumpers are installed on guide rod ends to provide extension bias and knee flexion control.
   4. Elastic Resistors: An elastic strap is attached to the wire frame to permit terminal deceleration. Two springs located in the plastic bushings are adjusted by cam rod to control the amount of knee bolt excursion. Weight applied to knee section depresses springs & allows contoured fibre surface to engage brake shoe to provide weight-bearing brake.
   5. Hydraulic: None
      Remarks: Cam rod has a graduated screw adjustment indicator (for springs).
5. Knee Stop Control and/or Terminal Deceleration
   1. Stick: None
   2. Rubber or Felt: Rubber on knee section engages with metal knee stop control.
   3. Straps or Cord: None
   4. Metal Knee Control: Carbon steel sheet metal provides pivoted attachment for brake shoe.
      Remarks: Brake shoe has screw type adjustment to control terminal deceleration.

Special Considerations:

1. Physical Dimensions:
   1. Supplied in rights and lefts, can be ordered in various knee widths (width determined by circumferential calf measurements).
   2. Parts and components are dimensioned in metric system.
2. Functional Controls:
   All controls provided are contained within the unit.
3. Adaptability:
   1. His unit can be used in conjunction with most foot-ankle units currently available.
   2. Will accommodate A/K stumps to within approximately 2" of knee center.
   3. Can be used with A/K adjustable leg and alignment duplication jig.

O&P Library > Orthotics and Prosthetics > 1959, Vol 13, Num 3 > pp. 75 - 79