1. Gait assessment:

this starts with a full clinical history, both from the patient and from any others involved, such as doctors, therapists or family members. Where a patient has previously had surgery, details of this should be obtained, if possible from the operative notes. History taking is followed by a physical examination, with particular emphasis on the neuromusculoskeletal system. In many laboratories, physical examinations are performed by both a doctor and a physiotherapist. Finally, a formal gait analysis is carried out.

2. Hypothesis formation:

the next stage is the development of a hypothesis regarding the cause or causes of the observed abnormalities. This hypothesis is often informed by the specific questions raised by the referring doctor. Time needs to be set aside to review the data, and consultation between colleagues, particularly those from different disciplines, is extremely valuable. Indeed, almost all of those using gait assessment as a clinical decision-making tool stress the value of this ‘team approach’. In forming a hypothesis as to the fundamental problem in a patient with a gait disorder, Rose (1983) emphasised that the patient’s gait pattern is not entirely the direct result of the pathology, but is the net result of the original problem and the patient’s ability to compensate for it. He observed that the worse the underlying problem, the easier it is to form a hypothesis, since the patient is less able to compensate.

3. Hypothesis testing:

this stage is sometimes omitted, when there is little doubt as to the cause of the abnormalities observed. However, where some doubt does exist, the hypothesis can be tested in two different ways – either by using a different method of measurement or by attempting in some way to modify the gait. Some laboratories routinely use a fairly complete ‘standard protocol’, including video recording, kinematic measurement, force platform measurements and surface electromyography (EMG). They will then add other measurements, such as fine wire EMG, where this is necessary to test a hypothesis. Other clinicians start the gait analysis using a simple method, such as video recording, and only add other techniques, such as EMG or the use of a force platform, where they would clearly be helpful. Rose (1983) opposed the use of a standard protocol for all patients, since some of the procedures turn out to be unnecessary and there is a risk of ending up with ‘an exhausted subject in pain’. The other method of testing a hypothesis is to re-examine the gait after attempting some form of modification, typically by the application of an orthosis to limit joint motion, a medication such as botulinum toxin to decrease spasticity, or by anaesthetising a muscle. The ultimate form of gait modification is the surgical operation, with retesting following recovery. However, this is a rather drastic form of ‘hypothesis testing’, which can be used only where there is a good reason to suppose that the operation will lead to a definite improvement.

Different types of gait analysis data may be useful for different aspects of the gait assessment. Information on foot timing may be useful to identify asymmetries and may indicate problems with balance, stability, pain etc. The general gait parameters give a guide to the degree of disability and may be used to monitor progress or deterioration with the passage of time. The kinematics of limb motion describe abnormal movements, but do not identify the ‘guilty’ muscles.

The most useful measures are probably the joint moments and joint powers, particularly if this information is supplemented by EMG data. Hemiparetic patients may show greater differences between the two sides in muscle power output than in any of the other measurable parameters, including EMG. Winter (1985) stressed the need to work backwards from the observed gait abnormalities to the underlying causes in terms of the ‘guilty’ motor patterns, using both the EMG and the moments about the hip, knee and ankle joints. He offered a method of charting gait abnormalities and a table giving the common gait disorders, their possible causes and the type of evidence which would confirm or refute them (Table 5.1). Although the next step, that of treatment, was not considered in detail, he suggested that once an accurate ‘diagnosis’ had been made, the therapist would be challenged to ‘alter or optimise the abnormal motor patterns’ which requires the understanding of the biomechanical cause–effect relationships necessary to improve gait.

Table 5.1 Common gait abnormalities, their possible causes and evidence required for confirmation

^* Note: there may be below normal extensor forces at one joint but only in the presence of abnormally high extensor forces at one or both of the other joints.

Reproduced with permission from Winter (1985).

Many others working in the field of clinical gait assessment have noted the difficulty of deducing the underlying cause from the observed gait abnormalities, because of the compensations which take place. A number of attempts have been made to simplify this process, by using a systematic approach. Computer-based expert systems are very suitable for this type of application and a number of such systems have been developed for clinical gait assessment. Since gait patterns are seldom clear-cut, such expert systems cannot generally use a fixed set of rules but rather need to learn to recognise patterns within complex sets of data. Techniques such as neural networks and fuzzy logic have been explored for this purpose (Chau, 2001). No doubt the number and quality of such systems will increase in the future. The following paragraphs describe how gait assessment is used for clinical decision making in a ‘typical’ laboratory. The details will, of course, differ from one laboratory to another, based on the skills and interests of the laboratory personnel, the facilities and equipment available, and the types of patient seen.

When the patient arrives at the facility informed consent is taken, a thorough history is then obtained and a physical examination is performed, by both a doctor, a physiotherapist, and sometimes others such as a prosthetist. Height, weight and a number of other measurements are made. The patient’s gait is video-recorded, viewing the patient from both sides and from the front and back. The ‘technological’ element of the gait analysis is performed, using a television/computer kinematic system and one or more force platforms. The number of cameras used is dictated largely by economics. Ideally, at least six cameras should be used but three can give acceptable data, particularly if measurements are made from only one side of the body at a time. Most laboratories record surface EMG, either on muscles which are selected on a case-by-case basis or on a standard set, such as gluteus maximus, quadriceps (in particular rectus femoris), medial and lateral hamstrings, triceps surae, tibialis anterior and the hip adductors. Depending on the clinical condition, fine wire EMG of selected muscles may be recorded, either at the same time or later. For example, Gage et al. (1984) reported that where a hip flexion contracture is present, their laboratory routinely records fine wire EMG from the iliopsoas, however this is not common clinical practice. There is variation in the protocols used, with some facilities recording kinetic, kinematic and EMG data at the same time, whereas others find it more convenient to record EMG separately.

Since great variability may exist between one walk and another, any single walk may not be representative, particularly if the patient hesitates or momentarily loses their balance. For this reason, a number of walks are recorded and the results examined for consistency. Depending on the clinical status of the patient, walks may be made under a number of different conditions, for example with and without shoes, with or without an orthosis, or using different walking aids. Activities such as rising from a chair or walking up and down steps can also be studied, however, it may not be possible to obtain force plate data.

Once preliminary reports on the history and physical examination have been prepared, the data processed and charts printed, the ‘team’ meets to discuss the case. The composition of the team varies considerably from one facility to another, but it would commonly consist of a doctor, a physiotherapist and a kinaesiologist or bio-engineer, with the optional addition of other doctors, physiotherapists, prosthetists, orthotists and podiatrists. Indeed, anyone with an interest in providing the best possible care for the patient may be invited to join the team to discuss a particular patient. In many facilities, the team includes the orthopaedic surgeon who will ultimately perform any necessary surgery.

The assessment begins with a careful review of the patient’s history and the physical examinations by the doctor and physiotherapist. The gait video recording is watched frame by frame and discussed and notes are made for inclusion in a final report. The general gait parameters are noted to determine the degree of disability and the effects of any changes in conditions, such as orthoses or walking aids. Different gait analysis systems provide different amounts of technical data on the patient’s gait and examination of the ‘charts’ can be a long and painstaking process. One of the most important parts of the assessment is to identify deviations from normal in the joint angles and to determine the cause of such deviations. This process is easier if joint moments and powers are available. Joint moments indicate in general terms which structures in the region of a joint are coming under tension and the degree of tension in them. Joint powers may help to discriminate between concentric muscle contraction, eccentric muscle contraction and passive tension in soft tissues. They can also distinguish between powerful and weak muscle contractions. The EMG also contributes to this process by identifying which muscles are electrically active and are thus candidates for developing tension at different times during the gait cycle.

Very briefly, interpretation of the gait analysis charts may involve the following steps. Commonly a comparison of the left to right sides is made when doing this.