Biomechanical and clinical outcomes with shock-absorbing insoles in patients with knee osteoarthritis: immediate effects and changes after 1 month of wear

Objectives: To examine the effectiveness of shock-absorbing insoles in the immediate reduction of knee joint load, as well as reductions in knee joint load, pain, and dysfunction after 1 month of wear, in individuals with knee osteoarthritis (OA).

Design: Pre-post design with participants exposed to 2 conditions (normal footwear, shock-absorbing insoles) with a 1-month follow-up.

Setting: University laboratory for testing and general community for intervention.

Participants: Community-dwelling individuals (N=16; 6 men, 10 women) with medial compartment knee OA.

Intervention: Participants were provided with sulcus length shock-absorbing insoles to be inserted into their everyday shoes.

Main outcome measures: Primary outcome measures included the peak, early stance peak, and late stance peak external knee adduction moment (KAM); the KAM impulse (positive area under the KAM curve); and peak tibial vertical acceleration. Secondary outcomes included walking pain, the Western Ontario and McMaster Universities Osteoarthritis Index pain subscale and total score, and a timed stair climb task.

Results: There was a significant reduction in the late stance peak KAM with shock-absorbing insoles (P=.03) during follow-up compared with the baseline test session. No other immediate or longitudinal significant changes (P>.05) in the other KAM parameters or peak tibial acceleration after use of a shock-absorbing insole were observed. However, significant improvements in all measures of pain and function (P<.05) were observed.

Conclusions: Shock-absorbing insoles produced significant reductions in self-reported knee joint pain and physical dysfunction with 1 month of wear in patients with knee OA despite no consistent changes in knee joint load. Further research using randomized controlled trials, with larger sample sizes and explorations into long-term use of shock-absorbing insoles and their effect on disease progression, is warranted.