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Page 8 of 15 Crowe et al. Plast Aesthet Res 2019;6:4 I http://dx.doi.org/10.20517/2347-9264.2018.70

Knee disarticulation
Knee disarticulation is a less commonly performed level of amputation with advantages and disadvantages
compared to the more proximal above-knee amputation (AKA). Early variations of the through-knee
amputation used a soft-tissue closure consisting of only skin and subcutaneous tissue, leaving a fragile
envelope prone to bone exposure if dehiscence occurred. Knee disarticulation was greatly improved by
use of the gastrocnemius muscle bellies to pad the distal end and thus provide vascularity and additional
[45]
cushioning to the closure and weight-bearing stump, respectively . The knee disarticulation is capable of
[46]
end bearing, is muscle-balanced in regards to flexion/extension and provides an excellent sitting platform
[47]
and long lever arm for wheelchair transfers in non-ambulatory patients . Leaving the femoral epiphysis
intact is important in children, as it will allow for continued longitudinal growth of the femur. In growing
patients, the arrest of longitudinal growth is carefully timed so that the prosthetic knee joint may better
approximate the length of the unaffected side.

A through knee amputation may pose challenges in regards to a stable and comfortable fit, though this is
not necessarily true if the prosthetist is experienced with creating the appropriate socket. This is particularly
problematic at the lateral femoral condyle, which may be prone to unbalanced loading and subsequent skin
breakdown.

Prosthesis and orthosis for knee disarticulations
The knee disarticulation results in a bulbous stump end, which is most evident when the femoral condyles
are left intact. Choice of liner becomes more important in this circumstance because it has the potential to
add even greater bulk to the distal residual limb. Several techniques are available to better accommodate
the bulky end - including inner protrusions and medial door openings to allow for passage of the condyles
and improved suspension of the prosthetic. The selection of a knee component will be discussed in greater
detail below; however, one consideration in knee disarticulation is the position of the prosthetic knee.
Analogous to the prosthetic foot/ankle with a Syme amputation, the prosthetic knee center resides more
distally than in the contralateral knee following disarticulation, which is more evident when the patient is
sitting. Subsequently, the shank portion of the lower leg prosthesis must be shortened to avoid leg-length
discrepancy and can cause some challenges in timing of the swing phase of gait on the prosthetic side.

Transfemoral amputation
The transfemoral, or AKA, is a less desirable level of amputation and is reserved for circumstances in which
a below- or through-knee amputation would not suffice to resolve the underlying pathology, allow for
enough tibial length for prosthetic fitting, or provide adequate tissue for closure of the residual limb. The
transfemoral amputation has been well demonstrated to increase the energy expenditure of ambulation
[8]
due to alteration of gait mechanics . Loss of contact with the tibia and an unopposed abductor mechanism
[48]
causes the femur to assume an abducted position, thus decreasing the efficiency of gait .
Ideally the transfemoral amputation is performed no more than 5-7 cm proximal to the knee joint, leaving
as long a lever arm as feasible while still allowing room for a prosthetic knee joint. Early techniques of
transfemoral amputation sacrificed the hip adductor muscles, which led to unopposed abduction and flexion.
Preservation of the adductor magnus and anchoring to the distal femur improves the position of the femur.
Overall, the transfemoral amputation tends to heal quickly and the residual femur has ample soft tissue on
all sides, especially when myodesis is pursued. This allows for earlier prosthetic fitting compared to more
distal amputations. However, there is less successful prosthetic ambulation in patients undergoing above
[49]
knee amputations .

Prosthesis and orthosis for above knee amputations
As with below-knee prostheses, socket design, interface, and suspension are necessary considerations in