Compensatory Function of the Subtalar Joint for Lower Extremity Malalignment

Table 1

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

	Total number	Reasons for deformation	Surgical procedure	Evaluation of subtalar alignment	Findings
Chandler et al. [10]	86	Varus and valgus knee OA	TKA	plane radiographs	The subtalar joint compensated the deformity of the knee.; There was no correlation between the knee and subtalar joint alignment.
Mullaji et al. [11]	165	Varus and valgus knee OA	TKA	plane radiographs	The hindfoot valgus decreased after TKA.; 87% of the subtalar joint continued to have valgus alignment even after TKA.
Norton et al. [12]	401	Varus and valgus knee OA	-	plane radiographs	Most 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]	71	Varus knee OA	TKA	plane radiographs	The 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]	75	Varus knee OA	TKA	plane radiographs	Calcaneal 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]	195	Varus knee OA	TKA	plane radiographs	Greater 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]	375	Varus knee OA	TKA	plane radiographs	The 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]	205	Knee RA with varus and valgus deformity	-	plane radiographs	Correlation 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 OA	HTO and LTO	plane radiographs	Hindfoot 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]	133	Varus ankle OA	-	plane radiographs	The subtalar joint compensates varus deformity of the ankle at the intermediate stage ankle OA, but not at the end stage.
Lee et al. [18]	154	Varus ankle OA	-	plane radiographs	Hindfoot 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]	233	Varus and valgus ankle OA	-	plane radiographs	Compensation 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]	88	Varus and valgus ankle OA	-	computed tomography	Compensation 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