Mechanical and physiological factors in knee joint contact mechanics: early changes following meniscectomy and conservative intervention strategies

Numerous biomechanical studies have provided evidence that laterally wedged insoles reduce the knee adduction moment during walking in healthy controls as well as patients with knee osteoarthritis potentially reducing the contact stress of medial tibial and femoral condyles. The knee adduction moment has been recognized as a suitable biomechanical marker for progression of knee osteoarthritis. However, recent clinical trials have not been able to confirm this potentially favourable effect. With the increasing prevalence of knee osteoarthritis and knee replacement surgery the demand for early conservative treatment modalities also increases.

The aim of this thesis was to 1) identify relationships between footwear and laterally wedged insoles in a healthy group, 2) to evaluate the mechanical and physiological factors of experimental pain when introducing a laterally wedged insoles to otherwise healthy subjects, and 3) to identify the acute effect of laterally wedged insoles on biomechanical markers in patients after an medial arthroscopic partial meniscectomy.

The results showed that shoe design and lateral wedges are equally important factors for changing the knee adduction moment, but the shoe designs tested did however not further improve or reduce the effect of lateral wedges. Second, experimental knee pain did not mediate the effect of lateral wedges in fact experimental knee pain has a larger impact on knee extension moment than knee adduction moment. Medial arthroscopic partial meniscectomy significantly increased the knee adduction moment 3-5 years postoperatively in an otherwise active group of patients when compared to a matched healthy group of people. Finally, lateral wedges can decrease knee adduction moment in medial arthroscopic partial meniscectomy patients, however not to the level of healthy matched controls.

In conclusion, although similar reductions can be achieved by choice of shoe design the difference between a neutral running shoe and Oxford leather shoes are similar in magnitude compared to the effect of lateral wedges in any type of shoe. Experimental pain does not seem to change the effect of lateral wedges independently. The knee adduction moment in patients 3-5 years after a medial arthroscopic partial meniscectomy was at a similar level to what is observed with advanced knee osteoarthritis. Therefore, laterally wedged insoles should be considered part of the mechanical solution to the increased risk of progression of knee osteoarthritis in this patient group.