Effects of Lateral Shoe Wedges and Toe-in Foot Progression Angles on the Biomechanics of Knee Osteoarthritis during Stationary Cycling

Exercise is important for individuals with knee osteoarthritis (OA) but certain activities can be painful and discourage participation. Cycling is commonly prescribed for OA but practically no previous literature exists. Due to their altered knee kinematics, OA patients may be at greater risk of OA progression or other knee injuries during cycling. The purpose of Study One was to investigate the effects of lateral wedges on knee joint biomechanics and pain in patients with medial compartment knee OA. The purpose of Study Two was to investigate the effects of toe-in foot progression angles on the same variables. Thirteen OA subjects and 11 healthy subjects participated. A motion analysis system and custom instrumented pedal was used to collect 5 pedal cycles of kinematics and kinetics during 2 minutes of cycling in one neutral and two lateral wedge conditions (5° and 10°) for Study One and 2 toe-in conditions (5° and 10°) for Study Two. Subjects pedaled at 60 RPM and 80 watts and rated their knee pain on a visual analog scale.

Study One: There was a 22% decrease in the knee abduction moment with the 10° wedge. This finding was not accompanied by a decrease in knee adduction angle or pain. Additionally, there was an increase in vertical and horizontal PRF which may negate the advantages of the decreased KAM.

Study Two: For the OA subjects, there was a 61% (2.7°) and a 73% (3.2°) decrease in peak knee adduction angle compared to neutral. This finding was not accompanied by a decrease in pain or KAM because of high inter-subject variability. A simple linear regression showed a positive correlation between Kelgren-Lawrence (K/L) score and both peak knee adduction angle and KAM.

For OA patients, cycling with a 10° lateral wedge or a decreased foot progression angle may be beneficial in slowing the progression of OA or minimizing other knee injuries. Patients with a higher K/L score may have greater risk of injury. More research is needed to investigate the joint contact forces as well as long term effects of riding with wedges or toe-in foot angles.