Review Question - QID 214416

An increased adductor moment during gait is associated with progression of medial knee osteoarthritis.

Altered joint loading during ambulation contributes to the onset and progression of knee osteoarthritis. The external knee adduction moment is considered a surrogate measure for the medial tibiofemoral contact force. An adduction moment is experienced by the knee when the ground reaction force passes medial to the center of the joint. This is seen when the knee has a varus mechanical alignment. An abnormally large peak adduction moment has been linked to increased pain and rate of disease progression. Strategies to decrease the knee adduction moment have been developed such as offloader braces.

Chehab et al. performed a biomechanical, clinical and MRI study on the progression of knee osteoarthritis. They found that the knee adduction and flexion moments were associated with decreases in medial femoral and tibial cartilage thickness, with the knee adduction moment being most associated with diminished medial femoral cartilage thickness and the knee flexion moment being most associated with diminished medial tibial cartilage thickness. They concluded that both knee adduction moment and knee flexion moment increase with medial arthritis and varus alignment, and must be taken into consideration when designing interventions that address knee osteoarthritis progression.

Manal et al. performed a biomechanical study in which they determined knee compartment loading utilizing video-based motion capture and electromyographic (EMG) recordings. They determined that peak adduction moment was the leading predictor of peak medial loading, and that peak knee flexor moment was also a significant predictor of peak medial joint loading. They concluded that the combined use of peak knee adductor and flexor moments provides a more accurate estimate of peak medial joint loading than the peak adduction moment alone.

Illustration A is a diagram that shows how a knee adduction moment is produced by a varus mechanical alignment.

Incorrect Answers:
Answer 1 and 4: These are two ways of stating the same thing. An increased knee flexion moment is associated with increased medial compartment loading.
Answer 2: An increased abduction moment is not associated with increased medial compartment loading.
Answer 5: This is incorrect. Both an increased adduction moment and an increased flexion moment are associated with increased medial compartment loading.