Posture perfect

POSTURE ASSESSMENT Clinical importance of posture Most medics and healthcare practitioners consider posture to be important, and as early as 1947 the Posture Committee of the American Academy of Orthopaedic Surgeons defined posture as “the arrangement of body parts in a state of balance that protects the supporting structures of the body against injury or progressive deformity”. This succinct definition highlights the most important aspects of posture: first, that it is an arrangement of body parts to create balance; and second, that if this balance is lost, then it is likely to have clinical implications.

Physiotherapist Chris Norris, looks at the importance of posture, outlining optimal posture, how to assess posture and the types of suboptimal posture.

When posture is optimal, there should be no pain and little muscle work needed to maintain it. Indeed, optimal posture combines both minimal muscle work and minimal joint loading. Where posture becomes suboptimal, we can expect both of these factors to increase. Figure 1 illustrates this. Blocks are arranged along a central line that passes through the centre of each block, in the same way that body segments are arranged along the posture line passing from the top of the head to between the feet. If one block moves forwards, its centre moves away from the line, causing it to tilt or fall. To prevent this, something must pull the block back in the opposite direction. In the case of the body, this opposite pull comes from soft tissues, especially muscle, meaning that the amount of muscle work is significantly increased. This is an immediate effect, but over time tissue adaptation will occur, with some tissues shortening and others lengthening. Soft tissue imbalance must therefore be corrected as part of posture re- education.

In addition, when one block lies directly on top of another, its a. Optimal alignment b. Suboptimal alignment (poor posture)

weight is distributed evenly along its whole contact surface. If one block moves forward relative to another, its weight is the same but this weight will be distributed over a smaller surface. The result is an increase in pressure (compression force) – just like a shoe with a stiletto heel causing more pressure on a floor than a shoe with a broader heel. Increased pressure gives increased loading and damage may result over time, as we saw with dance floors becoming pock- marked by stiletto heels in the 1960s.

Minimising joint loading over time is important. Joints rely on intermittent loading to flush nutrients contained within the synovial fluid across the joint surface and press them into the hyaline cartilage. Constant loading does not achieve the same effect, and point pressure caused by malalignment of a joint can produce thinning in joint cartilage. Correcting malalignment spreads pressure over a larger area, and restrengthening poor muscle increases the support to a joint. This effect (called load- sharing) takes some of the stress imposed on to a joint away from the joint structures such as cartilage, bone and ligaments and on to the muscles.

ASSESSING POSTURE Posture may be labelled static (still) or dynamic (moving). Static posture looks at one body segment relative to another along a vertical posture line. This type of assessment uses a plumbline and/or posture chart (Figure 2) and can suggest areas where further testing is required. For example, shortened tissue may develop trigger points requiring more attention by a soft tissue therapist. Dynamic posture also gives information about body segment alignment, muscle actions and motor skill. In my clinic we are mainly interested in walking, bending and sitting. In sport, actions such as running, jumping and throwing are examples of clinically important dynamic postures.

weight-bearing surface

normal muscle tone

overstretched muscle

Figure 1: Impact of suboptimal posture 20 lax muscle

Static posture assessment Static posture assessment begins with the subject standing behind a plumbline or posture screen. From the side the line should pass just in front of the ankle bone (lateral malleolus), just in front of the centre of the knee joint, through the greater trochanter of the hip, and then through the bodies of the lumbar vertebrae and the centre of the shoulder joint and ear. By passing through the knee joint centre, the knee is pressed straight and locks (extensor torque), meaning that we do not require any muscle activity in our quadriceps to stay standing upright. If the knee moves forwards, the line passes behind the knee centre, giving the knee a tendency to bend and unlock (flexor torque); this action must be resisted by activity in the quads. This muscle activity has two effects: first, it is tiring over time; second, the

The REPs Journal 2011;22(September):20-22