Table 1: Review of studies which assessed the subtalar joint compensation for the knee or the ankle deformity.

Total numberReasons for deformationSurgical procedureEvaluation of subtalar alignmentFindings

Chandler et al. [10]86 Varus and valgus knee OATKAplane radiographsThe subtalar joint compensated the deformity of the knee.
There was no correlation between the knee and subtalar joint alignment.

Mullaji et al. [11]165Varus and valgus knee OATKAplane radiographsThe hindfoot valgus decreased after TKA.
87% of the subtalar joint continued to have valgus alignment even after TKA.

Norton et al. [12]401Varus and valgus knee OA-plane radiographsMost of the compensation to angular deformity at the knee occurred in the subtalar joint.
There was a correlation between knee and hindfoot deformities in patients with a larger knee deformity (≥ 10°).

Takenaka et al. [8]71Varus knee OATKAplane radiographsThe subtalar joint alignment improved 3 weeks after TKA in the subtalar joint valgus group, and further improvement was noted 1 year following TKA.
The subtalar joint alignment did not improve after TKA in the subtalar joint varus group.

Okamoto et al. [13]75Varus knee OATKAplane radiographsCalcaneal pitch, naviculocuboid overlap and hindfoot pain with moderate varus deformity of knee (≤ 6° varus) improved after TKA, but those with severe varus deformity of knee (> 6°) did not improve after TKA.

Cho et al. [14]195Varus knee OATKAplane radiographsGreater improvements of hindfoot valgus occurred in patients with a severe varus deformity of the knee joint (≥ 10°) after TKA.
There was no further improvement in hindfoot alignment between 6 weeks and 2 years post-operatively.

Jeong et al. [7]375Varus knee OATKAplane radiographsThe variation of correction of varus knee alignment was significantly correlated with that of the valgus ankle and subtalar alignment after TKA.

Nakada et al. [15]205Knee RA with varus and valgus deformity-plane radiographsCorrelation exists between the knee and hindfoot alignments only in knees with a Larsen grade ≥ 4.
This correlation was stronger in patients with less damaged subtalar joints (Larsen grade ≤ 3).

Choi et al. [16]38 for HTO 
46 for LTO
Varus knee and ankle OAHTO and LTOplane radiographsHindfoot alignment was valgus in patients with advanced arthritis of the knee, but mild hindfoot varus deviation was seen in patients with advanced arthritis of the ankle.
Preoperative hindfoot valgus deviation was decreased after HTO, whereas the hindfoot alignment was changed to valgus deviation synchronizing to the ankle alignment after LTO.

Hayashi et al. [17]133Varus ankle OA-plane radiographsThe subtalar joint compensates varus deformity of the ankle at the intermediate stage ankle OA, but not at the end stage.

Lee et al. [18]154Varus ankle OA-plane radiographsHindfoot alignment was valgus in many ankles in stage II and IIIA, and the mean value was varus in stage IIIB and IV.

Wang et al. [19]233Varus and valgus ankle OA-plane radiographsCompensation of the subtalar joint was identified in 39% of valgus ankle OA and 53% of varus ankle OA.
The patients with no or mild degenerative changes of the subtalar joint may compensate the ankle malalignment

Krahenbuhl et al. [9]88Varus and valgus ankle OA-computed tomographyCompensation of the subtalar joint for the ankle deformity could only be verified for varus ankle osteoarthritis and not for valgus ankle osteoarthritis.
Subtalar joint alignment had no influence on the stage of ankle osteoarthritis, extent of the tibiotalar tilt and stage of subtalar joint osteoarthritis.

OA: osteoarthritis, TKA: total knee arthroplasty, HTO: high tibial osteotomy, LTO: low tibial osteotomy