Lateral Wedge Insoles (Recommendation Against)

Although lateral heel wedges had historical support for their use in knee arthritis, contemporary studies have not shown a reliable improvement in pain relief and no contemporary studies have shown sufficient functional improvement for patients suffering from knee arthritis to recommend using lateral wedge insoles. Lateral heel wedges can be prepared as an insert for the heel alone, or included in the heel of an independent arch support (i.e. lateral heel wedge arch support of LWAS) or built into shoe itself (as was used by Hinman et al 2016). In the arthritic knee, medial compartment compression forces are commonly increased, especially in the knee with varus tibiofemoral alignment. The knee adduction moment can be calculated by gait analysis. The lateral wedge is thought to change the knee adduction moment thus relieving medial compartment pressure, hence relieving arthritic pain.

Our literature review screening culled several papers for analysis. Baker and Goggins 2007 was a high quality study finding no important differences between insole and wedged insole. 90 patients were randomized to one treatment for 6 weeks followed by a 4-week washout period and then the opposite treatment. There were no major differences in pain during either phase of the study. More musculoskeletal symptoms and more blisters occurred with neutral insoles. No patient falls were attributed to the treatment alternatives.

Felson and Parke 2019 prescreened patients to eliminate those with patellofemoral OA and biomechanical non-responders. Lateral wedge insoles reduced knee pain, but the effect of treatment was small and was considered likely of clinical significance in only a minority of patients. 21 of 83 of patients did not show sufficient biomechanical correction. Only 28% of patients in the active phase of treatment had minimally important improvement whereas 22% of patients wearing neutral insoles reached the same level of improvement. 2 patients stopped treatment while wearing lateral wedge insoles (calf pain at night and increased knee pain) and 2 stopped while wearing neutral insoles (toe blister and increased knee pain). They also looked at volume of arthritic bone marrow lesions (BML) found by MRI and saw no significant difference in BML change between study and control groups.

In Bennell 2011, 89 patients with mild to moderate knee arthritis completed follow up with lateral insoles worn daily for 12 months. 90 patients completed follow up as the control group wearing neutral insoles. Pain relief after 12 months showed no significant difference between the groups. 

In Hsieh 2016, 90 patients with Kellgren-Lawrence Grade 2 or higher radiographic changes were randomized to either a rigid insole with lateral wedge arch support (LWAS) or a soft insole with lateral wedge. Dropout rate was 20% with rigid and 15.6% with soft insoles over the 3-month long study. They concluded that patients using the soft insole LWAS had improved pain and function. However, their primary data suggests better walking time and speed going up and down stairs with rigid LWAS. Furthermore, pain was improved with soft LWAS only at the 3-month mark. Authors suggested longer term follow up for soft insoles.

Hinman 2016 evaluated an unloading shoe with stiff lateral midsole and 5 degree lateral wedge insole in comparison to a standard walking shoe. 164 patients were enrolled with 96% retention during the 6 months study. 83 patients received the unloading shoes and the control shoes. 14 of 83 stopped wearing the unloading shoes for various reasons and 8 of 81 stopped wearing the control shoes. 160 completed primary outcome measures at 6 months. There was no significant difference between groups with regard to pain or function, although both groups did show improvement.

20% of participants with the study shoes reported ankle and foot pain whereas 9% of control shoe participants did so. There was no difference in reason to discontinue treatment (unloading shoe 4% versus 2% control). Other reported adverse events were back pain, hip pain, knee pain, knee stiffness/swelling and shin/calf pain. 2 of 83 experimental group patients reported increase in knee pain with the unloading shoe and 2 or 81 control patients reported that the conventional shoe did not relieve knee pain.

Toda 2004 followed 84 knee female arthritis patients were followed for one month wearing either a hard rubber insole or urethane insole secured to the foot with a subtalar strap used for ankle sprains. 12 mm lateral wedge was manufactured for both. 17 of the 42 rubber insole patients had complications (foot pain in 8; popliteal pain in 6; low back pain in 3) versus 8 of the 42 using urethane insoles (popliteal pain in 4; foot pain in 3; low back pain in 1). All patients improved by the Lequesne Index with the urethane group achieving statistically significant improvement.

Niazi 2014 was a comparison of off-loading knee brace versus lateral wedge insole. 120 patients with both radiographic medial compartment arthritis and gene varum were randomized to either knee brace or lateral wedge insole. Pain improvement with the knee brace group was statistically significant compared to the lateral wedge insole, but clinically minor (VAS 3.97 in the study group compared to 4.53 in controls).

In Hatef 2013, 118 of 150 patients completed the 2-month long study (101 women and 17 men). Half were given LWAS and the control group wore neutral insoles. Patient compliance was much worse in the LWAS group. They noted statistically significant decline in knee pain and EKFS in women in the LWAS, but not men. Overall, there was improvement in the LWAS group. There was a much higher noncompliance rate in the LWAS than with the neutral insoles with 29 of 57 patients stopping use of the insoles by weeks 5 to 6 of an 8-week study.

We identified one potential study within our literature which addressed the question of special shoe versus a conventional shoe. Nigg 2006 evaluated a training shoe which purports to convert a flat hard surface into “natural uneven ground”, thus prompting increased muscle activity in the lower extremity. The control shoe was a standard walking shoe. 58 patients were enrolled in the study group and 67 in the control group. Both groups had one patient drop out (cumbersome shoes in the study group and increased knee pain with the control shoe). Pain with walking was improved at 12 weeks in both groups, without between groups difference. The study shoe showed increased pain relief at 3, 6 and 12 weeks. The control shoe showed increased pain relief at 3 and 12 weeks. They also reported improved balance from baseline in the study shoe at 12 weeks which was not statistically significant.

Benefits/Harms of Implementation
Although lower extremity pain might be increased with either neutral insole or LWAS, there is no significant harm to the patient trying either option.

Cost Effectiveness/Resource Utilization
A standard insole or conventional walking shoe provided equivalent improvement in pain compared to lateral wedge arch support. Although the lateral wedge modifications are more expensive, the increased cost is not prohibitive and a patient attempting self-treatment could discontinue at any time with little loss of time effort or out of pocket cost.

Acceptability
Insoles are already commercially available and have long history of orthopaedic use. They can fit or be adapted to a variety of shoes, commonly already owned by the patient. Some studies reviewed (Hsieh 2016 and Hatef 2013) also described a relatively high dropout or non-compliance rate. While this does not imply frank harm to the patient, such data do suggest distinct potential for patient dissatisfaction with the treatment.

Feasibility
Although there are no immediately obvious limits to feasibility of implementing neutral insoles or LWAS for knee pain, Felson 2019 confirmed previous studies by showing 25% of their potential subjects did not correct knee adduction when using the lateral wedge.

Future Research
We did not identify any studies of sufficient size comparing a “walking shoe” versus a random or conventional shoe. The studies reviewed by the workgroup suggest that a walking shoe or a soft neutral insole might provide some degree of pain relief. Future studies addressing this treatment option could confirm some type of specialized yet commercially available shoe as beneficial to the patient with knee arthritis.