When having an amputation is a necessary measure and the affected area is around the knee, the opportunity sometimes presents itself to elect for either an Above Knee (AK) Amputation or a Through Knee (TK) Amputation.

However, prior to making this decision, there are numerous factors to be considered since there are clear advantages as well as distinct disadvantages with both procedures and the unique circumstances and lifestyle of the individual having the amputation need to be carefully considered. 

In this article we discuss the advantages, disadvantages and benefits of both procedures and, for ease of reference, we also provide a table that summarises each procedure at the end of our discussion.

Through-Knee Amputation

What exactly is a Through Knee Amputation?  Also known as Knee Disarticulation a Through Knee Amputation involves an amputation that is performed between bone surfaces instead of cutting through the bone itself.

Figure 1: Through Knee Amputation (Knee Disarticulation)

The prosthesis used for a Knee Disarticulation can be suspended from the condyles of the knee.  The condyles are the rounded protuberances found at the end of the knee bones.

  • The silicone sleeve

Prior the advent of the silicone sleeve, which is a gel-type sleeve made of silicone, urethane or similar materials, and works by creating an airtight seal between the skin of the residual limb and the top of the prosthesis, a Through Knee Amputation was advantageous since it helped with suspension.  However, the prosthesis can still be used successfully even without the silicone sleeve.

Figure 2: Silicone Sleeve
  • Advantages of having a Through Knee Amputation

There are definite advantages to having a Through Knee Amputation.  In the main:

  • Good functioning means that most of the body weight is taken as if the person is kneeling which imposes less stress on the residual limb as a whole.
    • The disarticulated knee takes 60% of the body weight and the long shaft of the femur can be used to take more of the weight.

Sean: Please insert Through Knee video here

  • Disadvantages of having a Through Knee Amputation

The disadvantages of having a Through Knee Amputation mainly involve:

  • Because a Through Knee disarticulation is a ‘long’ amputation, this impacts the limb in that the knee sticks out further than the other knee. 
    • One of the drawbacks is that tall people find it difficult to manoeuvre themselves in and out of a vehicle for instance.  However, most vehicles can be adjusted to accommodate the situation.
    • The residual limb may appear bulbous and the socket itself is also responsible for this type of appearance.
  • Benefits of a Through Knee Amputation
    • A Through Knee Amputation is end bearing which means that no weight is taken by the ischial tuberosity, otherwise termed the buttocks or also informally known as the ‘sit bones’, therefore it can be more comfortable to manage.
    • The silicone sleeve is not imperative since the procedure enables automatic suspension.
    • Rehabilitation time is a lot quicker since the bone is not cut.
    • The muscle structure is left intact which allows for greater control.

Above Knee Amputation

In the case where a Through Knee Amputation is not an option and an above knee amputation needs to be performed there are definite implications that need to be considered.

Image result for above knee amputation images
Figure 3: Louis Hoffman – a double amputee with left leg amputation above the knee

Overall, there is no real advantage of an Above Knee Amputation over a Through Knee Amputation except for cosmetic value and the fact that the system is not as cumbersome as the Through Knee procedure.  There are, however, some disadvantages.

  • Disadvantages of having an Above Knee Amputation
    • Unlike the Through Knee Amputation, an Above Knee Amputation cannot be weight bearing and a great deal of body weight is carried by the muscles.
    • Most of the body weight is carried through the ischial tuberosity.
    • The fitting of the prosthesis needs to be very precise to enable optimum functionality.

The table below summarises the advantages, disadvantages and benefits of both Above Knee and Through Knee Amputations

Comparison of Above Knee versus Through Knee Amputation
 
FactorsAbove Knee AmputationThrough Knee Amputation
AdvantagesDisadvantagesAdvantagesDisadvantages
CosmesisThe above knee amputation can achieve the same knee lengthThe residual limb may
appear bulbous and the socket itself is also responsible for this type of appearance
Muscle controlThe shorter the residual limb the more weight
taken by the muscles
from the prosthesis
RehabilitationN/AThe amputation is through the femur and takes
longer to heal
Faster healing as the knee
joint is disarticulated and no bone is cut
N/A
Silesian BeltN/AA Silesian Belt is a waist
belt that attaches the
prosthesis to the waist
Skin SuctionSkin suction forms a vacuum between the walls of the prosthetic socketN/A
N/A
N/A
SuspensionN/A
The silicone sleeve attaches to the residual limb and connects
it to the prosthesis
The prosthetist uses
the bulbous end of the residual limb for suspension
N/A
Weight bearingN/ATakes weight through the
ischial tuberosity (the
bone that we sit on)
The patient takes weight through
the condyles as if the person is
Kneeling which means It is easier and the prosthetic socket
does not need to go as high as an above knee socket

Final considerations

Overall, when weighing up the options as to which type of amputation is suitable for any particular individual, it is extremely important to take all contributing factors into account.  A person who has a more sedentary lifestyle in that they are not as physically active as some, may opt for the simplest solution.  However, someone who is keen on sporting activities such as tennis may want to investigate the various solutions that modern technology has to offer. Taking into account the individual circumstances of the patient, if the opportunity exists, it is more advantageous overall to opt for a Through Knee as opposed to an Above Knee Amputation.