Changes in ankle mechanical stability in those with knee osteoarthritis

Article Review by Robin J Lansman D.O., 

Sports Injury Tutor, British School of Osteopathy, London

This case control study aims to examine the correlation between Osteoarthritis in the knee and how that has an effect on the ankle sub-talar joint, by assessing it’s stability using an arthrometer. 

The ankle function was measured in A/P displacement as well as in inversion and eversion.  The study reports that among 27 million people in the United States suffering from osteoarthritis, the knee joint is the most commonly afflicted joint and it presents a large disruption to normal activities of daily living and exercise.  Disruption to the muscle function and particularly gait cycle is commonly observed to cause a compensation both above and below the knee joint.  This is perhaps something that Osteopaths observe as part of their normal patient assessment and something which is taken into account frequently.  There is a point when severe O/A of the knee reaches a point when O/A of the knee produces not just bio-mechanical changes in function of the ankle but actual arthritis at the ankle joint.

Consideration in patient management may therefore be that ankle rehabilitation should be a focus with any patient who is suffering from knee O/A.

This study was careful to exclude from its’ subjects any cases where there had been other traumas sustained in the hip area, surgical procedure or any other direct injury to the ankle, such as fracture.

A simple grading system was used to assess the osteoarthritic knee joints with zero representing no O/A, and then a scoring system used between 1, 2 and 3 to assess severity, independently assessed by two different orthopaedic surgeons.  Each patient was also assessed for pain levels,  level of stiffness and level of functional activity for the knee joint, so that each participant in the survey (15 subjects with O/A knee were compared with 15 healthy controls).

The sum assessment of the knee disability was scored out of a total of 96 points in total, to give an overall feeling of “disability” and how badly affected the particular individual   was by the O/A.  The ankle sub-talar joint was assessed using an arthrometer which basically allowed the foot to be fixed to an adjustable plate, which then in turn could be placed under different loadings to access the ankle function in different ranges of motion.

The data was recorded using a digital spatial kinematic linkage using customised software to assess the data that was collected.  The statistical analysis used on the case control design was a 2 x 2 case control design.

The study’s results were also made interesting because each of the arthritic knee patients also had the opposite knee and ankle tested, i.e. the side without the O/A. 

University patients with O/A knees exhibited considerable reduction in A/P joint displacement as well as in inversion and eversion when compared to the healthy group. 

It should also be pointed out that all subjects used for this study, even when they had O/A knee changes reported no actual symptoms at the ankle joint even though on testing there was considerable restriction in the ranges mentioned in the results.

Although the ankle joints may not have been symptomatic and may have exhibited dysfunction there was no X-ray taken of any of the reduced function ankle joints to actually confirm the presence of any early stage O/A in these ankle joints.  It does seem however that other results from another study by Tallroth et al, found significant correlation of the severity of the O/A and deviation of the ankle joint mechanics and alignment but in fact reported no clear relationship between ankle joint, mal-alignment and ankle O/A, although specific studies investigating ankle O/A exhibit similar restriction in range of movement in inversion, eversion and A/T displacement.  Moreover it seems that in this study where there was no frank O/A of the ankle were at a lesser stage of restriction than a population who actually suffer from ankle O/A.          .

It seems the most notable observation perhaps that Osteopathic practitioners can bear in mind is that observing gait can indicate a considerable amount of useful information to the clinical assessment of patients and that the varus or valgus of the knee has a direct relationship for the normal weight bearing function of the ankle and indeed, alterations at the hip with increased hip flexion and abduction, as well as at the ankle, for example when climbing stairs, are very easy to notice with a patient suffering from knee, mild to moderate knee O/A.

At a point in time the ankle sub-talar joint motion may not be able to compensate for the knee pathology.  A major limitation of the study is unlike an osteopaths ‘hands-on’ approach to examination and palpation, this study is measuring non-physiological movements using mechanical means to produce data, when in fact there is no measurement of natural physiologic motion, strength or function of the ankle sub-talar     joint.  A key finding however, and a suggestion to clinicians is the need to examine the ankle sub-talar joint mechanics and overall physiological motion to help maintain patient function in cases of the O/A knee.  Indeed patients may not be aware of ankle discomfort and therefore it is possible that this is not a reported area of symptoms that may or may not be assessed.

A suggestion of this study would be rehabilitation and treatment for patients with knee O/A should focus on the entire lower extremity to ensure function is maintained at all joints, in particular the ankle joint.  Additionally for them to do exercises for the whole lower extremities should be advised for mobility, joint functionality and possibly to prevent any changes for the ankle and the hip causing additional problems for these patients.

On an Osteopathic perspective it is uncertain whether Osteopathic practitioners utilise examination procedures that will incorporate the lower limb biomechanics in relation to spinal mechanics?

So taking this study a step further, might be using something such as a ‘Squatting’ test, which would then actually allow the observer to assess function between the ankle, knee, hip and through into the spinal function giving a more global impression of function.  Perhaps something for further discussion.

The measurement of ankle dysfunction on the opposite, supporting leg ie. the ankle on the side which is not affected by O/A in the knee is actually also doing more weight-bearing as a result of avoiding weight-bearing on the painful knee side.  As a result it would be expected that although the dysfunction is measurable in the ankle on the affected side,  was in fact weight-bearing compression loading through the supporting non-arthritic side may become more dysfunctional perhaps not when loaded using a mechanical arthrometer but indeed because of muscle loading changes which could produce stiffness and also a change in function in the ankle joint, something perhaps also that Osteopaths look at with a shift of weight-bearing which is a concern.   

It is quite commonly known that when mild arthritis occurs in one knee or one lower extremity joint it is common that the joint that wears out first is that of the supporting leg .because the patient has been adopting an antalgic posture tend to weight-bear even more heavily on the good side so in fact that side is the side that becomes arthritic at an accelerating rate and often is the knee joint surgery which needs replacement first even though it was the matter to suffer from many symptoms.

 In the meantime, the authors suggest the results of this study indicate a need to rehab both knees after a total knee replacement is done. The operated knee is important but the effect of the non-operated limb can't be ignored.

Reference:

Clare E. Milner, PhD, and Mary E. O'Bryan, BSEd. Bilateral Frontal Plane Mechanics After Unilateral Total Knee Arthroplasty. In Archives of Physical Medicine and Rehabilitation