Is increased knee moment risk for knee osteoarthritis?
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Increased Knee Moment and Risk for Knee Osteoarthritis
Introduction to Knee Moments and Osteoarthritis
Knee osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of cartilage and underlying bone in the knee joint. Mechanical factors, particularly knee joint moments during gait, play a significant role in the onset and progression of knee OA. This article explores the relationship between increased knee moments and the risk of developing knee osteoarthritis.
Knee Adduction Moment (KAM) and Osteoarthritis Risk
Elevated KAM and Medial Knee Loading
The knee adduction moment (KAM) is a critical biomechanical parameter that reflects the load distribution across the knee joint. Elevated KAM has been consistently associated with increased medial knee loading, which is a significant risk factor for the progression of medial knee osteoarthritis . Studies have shown that higher KAM is linked to greater cartilage loss and worsening of medial tibiofemoral cartilage defects over time.
KAM and Pain in Osteoarthritis
Increased KAM is also associated with higher levels of knee pain and disability in individuals with knee osteoarthritis. Research indicates that higher KAM during gait is correlated with greater self-reported pain and reduced physical function . This relationship underscores the importance of managing knee adduction moments to alleviate pain and improve quality of life in OA patients.
Knee Flexion Moment (KFM) and Its Protective Role
Lower Risk of Knee Pain with Higher KFM
Contrary to KAM, higher knee flexion moment (KFM) has been associated with a lower risk of developing knee pain in older adults. A study found that individuals with higher KFM during walking had a significantly lower incidence of frequent knee pain over a 24-month period. This suggests that promoting sagittal knee moments might be beneficial in preventing knee pain among the elderly.
KFM in Osteoarthritis Patients
However, in patients with existing knee osteoarthritis, greater KFM during the midstance phase of gait has been linked to moderate to severe pain. This indicates that while higher KFM may be protective against the onset of knee pain, it may exacerbate pain in those already suffering from OA.
Impact of Surgical Interventions on Knee Moments
ACL Reconstruction and Increased KAM
Individuals who have undergone anterior cruciate ligament (ACL) reconstruction often exhibit altered gait mechanics, including increased peak KAM. This biomechanical change is believed to contribute to the early onset of knee osteoarthritis in this population . The increased KAM post-ACL reconstruction highlights the need for targeted rehabilitation to mitigate OA risk.
Arthroscopic Partial Meniscectomy and Knee Loading
Patients undergoing arthroscopic partial meniscectomy (APM) also show increased KAM and KAM impulse in the operated leg compared to the contralateral leg. This increase in medial compartment loading may elevate the risk of developing knee osteoarthritis post-surgery.
Preventative and Therapeutic Implications
Gait Modifications and Toe-Out Angle
Modifying gait patterns, such as increasing the toe-out angle during walking, can reduce the knee adduction moment and potentially slow the progression of medial knee osteoarthritis. This biomechanical adjustment shifts the ground reaction force vector closer to the knee center, thereby decreasing medial knee loading.
Limb Realignment Surgery
Limb realignment surgeries, such as high tibial osteotomy (HTO), have shown promising results in reducing knee adduction moments and improving patient-reported outcomes over the long term. These surgical interventions can significantly alter load distribution during walking, leading to substantial improvements in knee function and pain relief.
Conclusion
Increased knee moments, particularly the knee adduction moment, are strongly associated with the risk and progression of knee osteoarthritis. While higher knee flexion moments may reduce the risk of developing knee pain in asymptomatic individuals, they can exacerbate pain in those with existing OA. Surgical interventions and gait modifications offer potential strategies to manage knee moments and mitigate the risk of knee osteoarthritis. Understanding and addressing these biomechanical factors are crucial for developing effective prevention and treatment approaches for knee OA.
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