The Role of Resistance Training in the Management of Knee Osteoarthritis
the deficit were caused primarily by atrophy, a pure muscle-strengthening approach would be taken. Alternatively, if the deficit were primarily in the ability to activate an essentially normal muscle cross-sectional area, attention might be directed towards removing the inhibitory sources that are preventing sufficient activation (such as pain and effusion) and re-training the patient to fully activate his or her muscles.
This probably reflects the overall low to moderate training intensity used in most resistance training studies involving people with knee OA.
Effects of Resistance Training Exercise on Muscle Strength in Knee Osteoarthritis A large systematic review was recently published assessing the effectiveness of isolated resistance training in people with knee OA.17 Fourteen RCTs were identified that measured parameters of muscle strength. In general, the quality of the reviewed studies was deemed by the authors to be moderately robust. All included trials compared the effects of isolated resistance training versus a non-exercising control group. Dynamic or isotonic training was the most common exercise modality. Machine-based resistance training was used in almost half of the studies, and a similar proportion used free weights, resistance bands and/or other household items such as stairs or chairs. Most training programmes lasted for one to six months; however, three longer-term studies were identified (18–30 months). In general, muscle strength improved significantly with resistance training (mean improvement 17.4%, range 10.5% decrease to 49.5% increase), with nine out of 14 studies reporting significant improvements. Relative effect sizes for strength outcomes ranged from -0.04 to 1.52 with an average of 0.38, indicating small to moderate effects. The authors suggested that the mean improvement in muscle strength of 17.4% is in the lower range of strength improvement observed in older non-OA cohorts, where strength gains may exceed 150%.18
function, but there was no evidence that the type of strengthening exercise influenced outcome. Thus, clinicians can prescribe the type of exercise that best suits the individual patient.
A more recent systematic review also concluded that resistance training improved pain and function by clinically meaningful amounts in people with knee OA.17
The effect sizes of resistance training are
The effects of resistance training on different severities of knee OA as well as on other outcomes such as health-related quality of life and depression are yet to be confirmed.17
modest but nevertheless similar to those that can be achieved by the use of analgesic drugs and non-steroidal anti-inflammatory medication.24
One further
benefit of resistance training that has been found is an increase in overall habitual physical activity levels.25
Resistance training is also important to This will be beneficial for
general health, particularly given that many people with knee OA are overweight or obese and have a number of co-morbidities such as diabetes and heart disease.26
minimise loss of lean muscle mass that would otherwise exacerbate muscle weakness in overweight patients with knee OA undergoing dietary-induced weight loss.27
High-intensity training (high resistance/load) might be expected to result in greater strength gains than low-intensity training in people with lower limb OA, but could potentially overload the joint and exacerbate symptoms. The only study comparing high- and low-intensity strengthening programmes found that both were equally beneficial for pain, function, walking time and muscle strength over eight weeks in people with knee OA.28
Importantly, adverse events
In knee OA, increases in muscle strength with resistance training are probably only partly explained by increases in muscle cross-sectional area.19
were no more likely to occur in the high-intensity group, contrary to what is often assumed. From a practical perspective, the high-intensity programme took 20 minutes less to complete, which may improve patient adherence. The findings of this study support the conclusion of a systematic review of resistance training, which noted that the dosage (modality, duration, volume, frequency, intensity) did not appear to be related to study outcomes.17
However, the mode of
A limited number of studies have evaluated whether exercise reduces muscle inhibition in people with painful knee OA. In the only randomised controlled trial, a six-month home exercise programme aimed at strengthening the quadriceps and, to a lesser extent, the hamstrings led to modest changes (5–6%) in voluntary quadriceps activation as measured via twitch superimposition.20
Other
non-randomised studies have also found reduced quadriceps inhibition following a strengthening programme.21,22
Further research
is needed to investigate the relative contributions of neural adaptation, pain changes and muscle hypertrophy to the strength increases observed and their relationships with function.
Effects of Resistance Training Exercise on Symptoms of Knee Osteoarthritis
Strengthening exercises may be performed in a variety of modes including isometric, isotonic, isokinetic, concentric and eccentric. They may also be performed in an open kinetic or closed kinetic chain manner. Open kinetic chain exercises at the knee are non-weight-bearing, while closed kinetic chain exercises are typically weight-bearing involving multiple joints and are thought to be more functional. A meta-analysis published in 2004 identified 22 trials of strengthening exercise on individuals with knee OA employing a variety of modes.23
The results of this meta-analysis found that resistance exercise was effective in terms of improving pain and EUROPEAN MUSCULOSKELETAL REVIEW
delivery may be important, with a Cochrane review of land-based exercise for knee OA noting significantly greater improvements in pain and function with more than 12 directly supervised exercise sessions.29
There are few long-term studies of the effects of resistance training in people with knee OA. A recent study found that a home-based, self-managed programme of simple knee-strengthening exercises over a two-year period significantly reduced knee pain and improved knee function in overweight and obese people with knee pain.30 However, patient adherence to exercise declines rapidly over time and is an important factor in determining the long-term effectiveness of exercise for patients with OA.31
Adherence is improved when
patients receive attention from health professionals rather than following a primarily home-based exercise programme.32
Better
adherence is related to the patient’s belief in the effectiveness of the intervention and his or her understanding of the pathogenesis of OA (those who are less adherent tend to believe that OA is part of the natural ageing process or that it is simply a ‘wear and tear’ disease). Self-efficacy, or belief in one’s ability to perform tasks, is also associated with higher adherence and better outcome.33
Effects of Resistance Exercise on Knee Osteoarthritis Disease Progression A limited number of clinical trials have directly evaluated the effect of strengthening exercise on structural disease progression as
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