AFO Alignment Guidelines

A correct alignment is critical for a functional orthosis. To ensure that the patient walks safely in all gait phases, the different orthosis construction characteristics and how they affect the overall orthosis’ alignment, and thus the patient as well, must already be considered when the orthosis is being planned.

This online tutorial reflects the alignment of an AFO (Ankle Foot Orthosis) and the effects through varied adjustments during the various gait phases

Step 1/2

The loading line should be located in the first third (from anterior to posterior) up to half of the supportive area. The supportive area in mid stance is defined by the heel lever and the rolling-off area. For the loading line to fall centrally, measures ought to be taken, such as a posterior offset of the heel or an anterior offset of the mechanical rolling-off area.

Step 2/2

The knee’s pivot point should be located behind the loading line. As a result, especially in case of shortenings, the offset of the anatomical foot must be considered in regards to the supportive area. Concerning motion limits of the ankle, knee and/or hip joint, the knee’s pivot point can often remain behind the loading line as well. If the knee’s pivot point shall be located before the loading line due to motion limits, the patient’s muscle strength must be very good (see right side of the picture). In case of paralyses, the patient can not sufficiently secure the knee with this alignment and thus needs a lock function for the stance phase.

Step 1/13

The dorsiflexion stop affects the gait phases mid stance, late mid stance, terminal stance and pre swing. In these phases, the dorsiflexion is limited by the dorsiflexion stop. In the other phases, with correct alignment, the dorsiflexion stop is not reached. The effects on the gait phases must always be considered in regards to the toe spring and the forefoot construction.

Step 2/13

Dorsiflexion Stop in mid stance
In case of system joints without a dorsiflexion stop, the patient should activate the muscle groups of the plantar flexors (in particular the soleus and the gastrocnemius muscle). As a result:

  • the angle from lower leg to foot in dorsiflexion direction is limited by the muscles;
  • it is possible that the leg can take the load, because a knee flexion is only possible to a lesser extent, limited or slowed down by the muscles;
  • the body's centre of gravity does not drop.

Step 3/13

Dorsiflexion Stop in mid stance
In case of system joints with a static dorsiflexion stop, the stop is reached here. As a result:

  • the angle from lower leg to foot in dorsiflexion direction is limited;
  • it is possible that the leg can take the load, because the knee joint can not be flexed any further as a knee extending moment is in effect;
  • the body's centre of gravity does not drop.

Step 4/13

Dorsiflexion Stop in mid stance
In case of system joints with a dynamic dorsiflexion stop, the first spring contact is made here. As a result:

  • the angle from lower leg to foot in dorsiflexion direction still varies to a small extent towards the spring’s resistance;
  • it is possible that the leg can take the load, because a knee flexion against the spring’s resistance is only possible to a small extent;
  • the body's centre of gravity does not drop.

Step 5/13

Dorsiflexion Stop in late mid stance
In case of system joints without a dorsiflexion stop, the muscles of the plantar flexors remain active here. As a result:

  • the further dorsiflexion  is controlled;
  • the motion is completely limited at a certain point;
  • the heel still remains on the floor at this point;
  • the body's centre of gravity acts physiologically and drops slightly;
  • the loading line can fall before the knee’s pivot point without the knee being flexed;
  • the leg can still take the load on this side.

Step 6/13

Dorsiflexion Stop in late mid stance
In case of system joints with a static dorsiflexion stop, the patient can not stand in this position as this requires a further dorsiflexion from mid stance to late mid stance. The system joint prevents that, and thus, this phase is skipped.

Step 7/13

Dorsiflexion Stop in late mid stance
In case of system joints with a dynamic dorsiflexion stop, the dorsiflexion motion is limited here. As a result:

  • the further dorsiflexion  up to the final limitation is controlled;
  • the heel still remains on the floor at this point;
  • the body's centre of gravity acts physiologically and drops slightly;
  • the loading line can be shifted before the knee’s pivot point without the knee being flexed, because a knee extending moment is in effect;
  • the leg can still take the load on this side.

Step 8/13

Dorsiflexion Stop in terminal stance
In case of system joints without a dorsiflexion stop, the plantar flexors remain fully active here. As a result:

  • the heel does lift from the ground;
  • the body's centre of gravity remains high;
  • the knee is not flexed further, even if the loading line falls before the knee’s pivot point;
  • the step length is physiological and matches the contralateral side;
  • the leg can still take the load on this side.

Step 9/13

Dorsiflexion Stop in terminal stance
In case of system joints with a static dorsiflexion stop, the dorsiflexion motion is still completely limited here. As a result:

  • the heel does lift from the ground;
  • the body's centre of gravity remains high;
  • the knee is not flexed further, even if the loading line falls before the knee’s pivot point;
  • the step length is physiological and matches the contralateral side;
  • the leg can still take the load on this side.

Step 10/13

Dorsiflexion Stop in terminal stance
In case of system joints with a dynamic dorsiflexion stop, the dorsiflexion motion is still completely limited here. As a result:

  • the heel does lift from the ground;
  • the body's centre of gravity remains high;
  • the knee is not flexed further, even if the loading line falls before the knee’s pivot point;
  • the step length is physiological and matches the contralateral side;
  • the leg can still take the load on this side.

Step 11/13

Dorsiflexion Stop in pre swing
In case of system joints without a dorsiflexion stop, the plantar flexors still remain active. As a result:

  • a slight plantar flexion takes place;
  • the knee is slightly flexed;
  • the body's centre of gravity remains high;
  • the load is on the contralateral side.

Step 12/13

Dorsiflexion Stop in pre swing
In case of system joints with a static dorsiflexion stop, the dorsiflexion motion is still limited. As a result:

  • the knee is flexed;
  • the swing phase is prepared;
  • the body's centre of gravity remains high;
  • the load is on the contralateral side.

Step 13/13

Dorsiflexion Stop in pre swing
In case of system joints with a dynamic dorsiflexion stop, the spring unit is decompressed here. As a result:

  • a slight plantar flexion takes place;
  • the knee is slightly flexed;
  • the body's centre of gravity remains high;
  • the load is on the contralateral side.

Step 1/4

The toe spring affects the gait phases terminal stance, pre swing and initial swing. It does not affect any other phases. The effects on the gait phases must always be considered in regards to the dorsiflexion stop and the forefoot construction.

Step 2/4

Toe Spring in terminal stance
In case of a long rigid or long partially flexible foot piece, the toe spring results in:

  • a step, which is neither shortened nor discontinued while shifting into terminal stance and a heel, which is lifted while the load does not need to be taken from the leg;
  • a step length, which adapts to the contralateral side;
  • a knee, which remains extended.

In case of a short foot piece, the toes are extended and thus the same effect is achieved.

Step 3/4

Toe Spring in pre swing
In case of a long rigid or long partially flexible foot piece, the toe spring results in:

  • a flexed knee, initiating the flexion in initial swing.

In case of a short foot piece, the toes are extended and thus the same effect achieved.

Step 4/4

Toe Spring in initial swing
In case of a long rigid or long partially flexible foot piece, the toe spring results in:

  • a leg, which does not need a vaulting/a circumduction or to be lifted additionally in order to be able to swing. The patient does not get stuck with the toes.

In case of a short foot piece, the toes are extended and thus the same effect is achieved.

Step 1/3

The orthosis’ foot piece can either:

  • be produced rigidly up to the rolling-off area and end there (short foot piece);
  • be produced rigidly up to the rolling-off area and flexibly up to the complete inner shoe dimension (partially flexible foot piece);
  • be produced rigidly up to the complete inner shoe dimension (rigid foot piece).

If the foot piece is either rigid or flexible does not depend on the material but on the mobility of the forefoot in comparison to the hindfoot. A rigid forefoot can not be moved against the heel. Here  you can find information about the production.
A toe spring must be taken into consideration in case of a rigid or partially flexible foot piece, so they can fulfil their function properly. In addition, the forefoot lever co-operates with the dorsiflexion stop. The forefoot affects the gait phases terminal stance and pre swing. It does not affect any other phases.

Step 2/3

Forefoot in terminal stance
In case of insufficient toe flexors, a rigid forefoot results in:

  • a hindfoot which is limited in its motion against the forefoot (in toe extension´s direction);
  • the load remaining on the leg;
  • the heel being lifted;
  • the body's centre of gravity remaining high;
  • the knee being not flexed too much.

A partially flexible forefoot has the same effect. But, therefore, the toe flexors must be active.
Without a forefoot on the foot piece, this work must be done by the toe flexors alone.

Step 3/3

Forefoot in pre swing
A rigid forefoot prevents a toe extension, which still increasingly occurs in this phase, from happening. As a result:

  • the knee is increasingly flexed;
  • the heel is being lifted higher;
  • the contact to the floor is decreased.

A partially flexible forefoot enables this physiological, increased toe extension. But, therefore, the toe flexors must be able to counteract actively. As a result: 

  • the knee angle can remain physiologically;
  • the heel is not being lifted higher.

Without a forefoot, the same is happening as with a partially flexible foot piece. But, therefore, the toe flexors must be able to completely counteract actively.

Step 1/4

The foot piece’s mechanical rolling-off area separates the forefoot from the heel construction and defines an axis by doing so. The anatomical rolling-off area can significantly differ from the mechanical one. If the deviation should be too high, a rigid forefoot construction can be taken into consideration, even if it is not indicated on a muscular level.
The mechanical rolling-off area affects the gait phases mid stance, late mid stance and terminal stance.
The functionality of the mechanical rolling-off area significantly depends on the forefoot construction, the dorsiflexion stop and the pitch.

Step 2/4

Rolling-Off Area in mid stance
The mechanical rolling-off area limits the stance area (supportive area) distally. This way, it expands from the heel lever to the mechanical rolling-off area.
The GRF (ground reaction force) vector must fall into the supportive area in order for the legs to be able to take the load. This is an important task for the orthotist or qualified/trained expert, especially when height compensations and knee flexion contractures are involved.

Step 3/4

Rolling-Off Area in late mid stance
The mechanical rolling-off area limits the stance area (supportive area) distally. This way, it expands from the heel lever to the mechanical rolling-off area.
The GRF (ground reaction force) vector must fall into the supportive area in order for the legs to be able to take the load. This is an important task for the orthotist or qualified/trained expert, especially when height compensations and knee flexion contractures are involved. 

Step 4/4

Rolling-Off Area in terminal stance
The mechanical rolling-off area contains one axis. The foot rotates around this axis, because the GRF vector falls ahead of the rolling-off area, now. This way, the heel is lifted from the ground. The body's centre of gravity remains high.

Step 1/6

The mechanical heel lever represents an axis. The foot rotates around this axis. In addition, the heel lever limits the stance area (supportive area) proximally. The anatomical heel lever can significantly differ from the mechanical one. The heel lever affects the gait phases initial contact, loading response, early mid stance, mid stance and late mid stance.

Step 2/6

Heel Lever in initial contact
The mechanical heel lever represents the first ground contact.

Step 3/6

Heel Lever in loading response
The foot rotates around the mechanical heel lever. This results in:

  • a plantar flexion, if the system ankle joint allows such (plantar flexion: free or against spring force) - otherwise, there will solely be a tibia inclination;
  • a tibia inclination and a knee flexion, if the system knee and ankle joint allow such (plantar flexion: free or against spring force; flexion: free) - otherwise, there will solely be a tibia inclination or in case of a locked system knee joint an inclination of the hip and thigh.

Step 4/6

Heel Lever in early mid stance
The mechanical heel lever limits the stance area (supportive area) proximally. This way, it expands from the heel lever to the mechanical rolling-off area.
The GRF (ground reaction force) vector must fall into the supportive area in order for the legs to be able to take the load. This is an important task for the orthotist or qualified/trained expert, especially when height compensations and knee flexion contractures are involved.

Step 5/6

Heel Lever in mid stance
The mechanical heel lever limits the stance area (supportive area) proximally. This way, it expands from the heel lever to the mechanical rolling-off area.
The GRF (ground reaction force) vector must fall into the supportive area in order for the legs to be able to take the load. This is an important task for the orthotist or qualified/trained expert, especially when height compensations and knee flexion contractures are involved.

Step 6/6

Heel Lever in late mid stance
The mechanical heel lever limits the stance area (supportive area) proximally. This way, it expands from the heel lever to the mechanical rolling-off area.
The GRF (ground reaction force) vector must fall into the supportive area in order for the legs to be able to take the load. This is an important task for the orthotist or qualified/trained expert, especially when height compensations and knee flexion contractures are involved.

Step 1/22

Similar to the dorsiflexion stop, the plantar flexion stop can be realised in a number of ways and the effects differ, depending on the gait phase. Instead of a plantar flexion stop, this is often referred to as a foot lifting effect.

The plantar flexion stop affects the gait phases initial contact, loading response, early mid stance, pre swing, initial swing, mid swing and terminal swing.

It does not affect the other three gait phases, because here, the GRF vector falls before the system ankle joint’s pivot point and the dorsiflexion stop is reached. The contact to the plantar flexion stop is lost or is no longer in effect.

Step 2/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial contact
The heel lever gets in contact to the ground and results in a plantar flexion, which - in co-operation with the tibia inclination - initiates the loading response. This is the physiological process and should be reached, whenever possible. The plantar flexion stop can limit the plantar flexion here, or enable a resistance against this motion. The latter results in a controlled plantar flexion.

Without Plantar Flexion Stop:
If a plantar flexion without limitation or without resistance is possible, the situation is the same as for the variation against the spring force. But, therefore, the dorsal flexors must be active.

Step 3/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial contact
Without Plantar Flexion Stop, with Dorsiflexion Assist:
If a plantar flexion without limitation or without resistance is possible, the situation is the same as for the variation against the spring force. But, therefore, the dorsal flexors must be active.
This is also valid for system joints with a spring unit, if the spring is just very weak.

Step 4/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial contact
Dynamic Plantar Flexion Stop:
If a plantar flexion against a spring resistance is possible (not in case of a NEURO SPRING/VARIO-SPRING), this results in:

  • a physiological plantar flexion;
  • a physiological tibia inclination;
  • a physiological slight knee flexion;
  • a high remaining body's centre of gravity;
  • a symmetric step length.

Step 5/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial contact
A static plantar flexion stop in the shape of any kind of motion limitation, does not enable a plantar flexion. As a result:

  • a physiological plantar flexion cannot take place;
  • the angle from lower leg to foot remains the same;
  • the lower leg is significantly more accelerated forwards;
  • the knee is highly flexed;
  • the hip is moved forward in a highly accelerated way;
  • the body's centre of gravity drops due to the increased flexion;
  • the step length on the contralateral side is shortened as the patient tries to compensate the feeling of insecurity.

Step 6/22

Plantar Flexion Stop/Plantar Flexion Limitation in loading response
This phase is physiologically characterised by a plantar flexion. The foot reaches complete contact to the ground and the lower leg moves forward while the knee is flexed. The plantar flexion stop can limit the plantar flexion here or enable a resistance against this motion. The latter results in a controlled plantar flexion.

Without Plantar Flexion Stop:
If a plantar flexion without limitation or without resistance is possible, the situation is the same as for the variation against the spring force. But, therefore, the dorsal flexors must be active.

Step 7/22

Plantar Flexion Stop/Plantar Flexion Limitation in loading response
Without Plantar Flexion Stop, with Dorsiflexion Assist:
If a plantar flexion without limitation or without resistance is possible, the situation is the same as for the variation against the spring force. But, therefore, the dorsal flexors must be active.
This is also valid for system joints with a spring unit, if the spring is just very weak.

Step 8/22

Plantar Flexion Stop/Plantar Flexion Limitation in loading response
Dynamic Plantar Flexion Stop:
If a plantar flexion against a spring resistance is possible, this results in:

  • a physiological plantar flexion;
  • a physiological tibia inclination;
  • a physiological slight knee flexion;
  • a high remaining body's centre of gravity;
  • a symmetric step length.

Step 9/22

Plantar Flexion Stop/Plantar Flexion Limitation in loading response
A static plantar flexion stop in the shape of any kind of motion limitation does not enable a plantar flexion. This results in skipping this phase.

Step 10/22

Plantar Flexion Stop/Plantar Flexion Limitation in early mid stance
The plantar flexion is reduced, because the lower leg moves forward. 

Without Plantar Flexion Stop:
If a plantar flexion without limitation or without resistance is possible, this has no effects here.

Step 11/22

Plantar Flexion Stop/Plantar Flexion Limitation in early mid stance
Without Plantar Flexion Stop, with Dorsiflexion Assist:
If a plantar flexion without limitation or without resistance is possible, this has no effects here.

Step 12/22

Plantar Flexion Stop/Plantar Flexion Limitation in early mid stance
Dynamic Plantar Flexion Stop:
If a plantar flexion against a spring resistance is possible, this results in a supported dorsiflexion.

Step 13/22

Plantar Flexion Stop/Plantar Flexion Limitation in early mid stance
Static Plantar Flexion Stop:
If the plantar flexion is limited, this phase is skipped.

Step 14/22

Plantar Flexion Stop/Plantar Flexion Limitation in pre swing
Without Plantar Flexion Stop (with or without dorsiflexion assist):
If a plantar flexion without limitation or without resistance is possible, this has no effects here.

Step 15/22

Plantar Flexion Stop/Plantar Flexion Limitation in pre swing
Dynamic Plantar Flexion Stop:
In case of a very strong spring resistance and due to the leverage ratio, a plantar flexion is not possible in this phase. In case of weaker resistances, the same applies as for without plantar flexion stop (with or without dorsiflexion assist). 

Step 16/22

Plantar Flexion Stop/Plantar Flexion Limitation in pre swing
Static Plantar Flexion Stop:
A plantar flexion stop can prevent the physiological plantar flexion stop.

Step 17/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial swing
Without Plantar Flexion Stop:
The foot must be kept high by the dorsal flexors in order for a physiological, functional shortening of the leg to happen and to prevent compensatory movements (circumduction, vaulting etc.).

Step 18/22

Plantar Flexion Stop/Plantar Flexion Limitation in initial swing
Without plantar flexion stop, with dorsiflexion assist or a dynamic plantar flexion stop (with a sufficient spring resistance) as well as a static plantar flexion stop result in: 

  • a physiological, functional shortening of the leg;
  • no compensatory movements (circumduction, vaulting etc.).

Step 19/22

    Plantar Flexion Stop/Plantar Flexion Limitation in mid swing
    Without plantar flexion stop, the pretibial muscles must be active for:

    • a physiological, functional shortening of the leg;
    • the prevention of compensatory movements (circumduction, vaulting etc.).

    Step 20/22

    Plantar Flexion Stop/Plantar Flexion Limitation in mid swing
    Without plantar flexion stop with dorsiflexion assist, dynamic and static plantar flexion stop enable:

    • a physiological, functional shortening of the leg;
    • the prevention of compensatory movements (circumduction, vaulting etc.).

    Step 21/22

    Plantar Flexion Stop/Plantar Flexion Limitation in terminal swing
    Without plantar flexion stop, the pretibial muscles must be active for: 

    • a physiological, functional shortening of the leg;
    • the prevention of compensatory movements (circumduction, vaulting etc.).

    Step 22/22

    Plantar Flexion Stop/Plantar Flexion Limitation in terminal swing
    Without plantar flexion stop with dorsiflexion assist, dynamic and static plantar flexion stop, enable:

    • a physiological, functional shortening of the leg;
    • the prevention of compensatory movements (circumduction, vaulting etc.).

    Last Update: 20 August 2020

    FIOR & GENTZ

    Gesellschaft für Entwicklung und Vertrieb von orthopädietechnischen Systemen mbH

    Dorette-von-Stern-Straße 5
    D-21337 Lüneburg

    Phone: +49 4131 24445-0
    Fax: +49 4131 24445-57
    Email: info(at)fior-gentz.de


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