Medial knee osteoarthritis is a condition which many clinicians see and has been described in literature as “a major public health problem”. This prospective cohort study examines the effect of mechanical factors on the progression of medial knee arthritis and gives food for thought in terms of management with conservative therapies.

 

Higher dynamic medial knee load predicts greater cartilage loss over 12 months in medial knee osteoarthritis

Kim L Bennell, Kelly-Ann Bowles, Yuanyuan Wang, Flavia Cicuttini,

Miranda Davies-Tuck, Rana S Hinman (2011).

Annals of Rheumatic Diseases. 70(10) pp.1770-4

 

Overview:


Increased medial knee joint load is a mechanical force which is believed to be a key factor in the development of medial knee arthritis. This study sought to investigate the relationship between medial joint loading during gait and the progression of arthritis. They found that higher “knee adduction moment impulse” was associated with greater loss of medial tibial cartilage volume over a 12 month period, meaning that it is a risk factor for disease progression.


What it all means:


Essentially, because joint load is modifiable with conservative therapies (such as physiotherapy or foot orthoses), appropriate interventions may slow down the disease process.

 

Key points:

  • Participants were recruited with medial knee pain and medial osteophytes or joint narrowing on x-ray.

 

  • Lateral wedged insoles were compared against flat control insoles. Baseline measurements of medial knee load were then taken before intervention.

 

  • Peak “knee adduction moment” (KAM) and KAM impulse were both measured at baseline.

 

  • MRI’s of the knee were taken at baseline and at 12 months for comparison.

 

  • KAM impulse was found to have the greatest effect on loss of medial knee cartilage.

 

  • KAM impulse means that it considers both magnitude and duration of the adduction moment, so it gives more comprehensive information about knee load rather than just measuring the peak KAM which just measures one point in stance.

 

  • It is unclear how mechanical loading stresses cartilage but, it is thought to involve chondrocyte death, disruption of the extracellular matrix and microfractures within the subchondral cortical end plate.

 


Putting it into practice:

  1. While the paper clearly states that more research is needed outside of a laboratory environment, it does support “load modifying interventions” such as gait retraining, braces, footwear and exercise.

 

  1. Further research has supported the use of laterally wedged prefab insoles for reducing KAMs. If you decide to try this in clinic, start gradually with a low degree of wedging and run the wedging along the entire lateral edge of the insole so that the whole foot everts and reduces the adduction moment at the knee. Make sure you have a valgus support under the arch to reduce eversion at the STJ and ankle joint.

 

  1. Always carry out a full biomechanical assessment first as any orthotic modification can affect any of the joints in the lower limb, not just the knee.

 

  1. Managing joint loads and the effects on arthritis has received a lot of attention in the literature in recent years. Keeping up to date with new research is paramount to improving patient care and quality of life.


Professor Kim Bennell will be addressing this at the Biomechanics Summer School in June along with other leading speakers in this field.