4.1 Posture and Gait Analysis

Why Posture and Gait Analysis Matters on Part III

Posture and gait analysis is a core observational skill tested on the National Board of Chiropractic Examiners (NBCE) Part III Neuromusculoskeletal (NMS) Examination. These questions typically present a brief clinical vignette describing an observed deviation in standing alignment or a described walking pattern, then ask the candidate to identify the underlying structural, muscular, or neurological cause. Because posture and gait findings are the first data gathered in any physical examination, they also set up follow-on questions about which orthopedic or neurological test should be performed next.

Static Posture Assessment

Static posture is evaluated with the patient standing relaxed in anatomical position, viewed from anterior, posterior, and lateral perspectives, ideally against a plumb line or posture grid.

Reference landmarks (lateral view) — the plumb line should pass through:

• External auditory meatus
• Bodies of the cervical vertebrae
• Tip of the shoulder (acromion)
• Midpoint of the trunk, through the lumbar vertebral bodies
• Greater trochanter of the femur
• Slightly anterior to the midline of the knee
• Slightly anterior to the lateral malleolus

Common postural distortions and their typical drivers:

Anterior-view landmarks that should be level and symmetrical include the eyes, ear lobes, acromion processes, iliac crests, and knee/ankle position; posterior-view landmarks add the inferior scapular angles and gluteal fold height. Any asymmetry is documented and correlated with palpation and orthopedic findings rather than diagnosed from observation alone.

Dynamic Posture: The Normal Gait Cycle

Gait is assessed dynamically as the patient walks, ideally for several full cycles. One gait cycle runs from heel strike of one foot to the next heel strike of the same foot, and is divided into:

• Stance phase (about 60% of the cycle): heel strike, foot flat, midstance, heel-off, toe-off
• Swing phase (about 40% of the cycle): acceleration, mid-swing, deceleration

Normal gait requires coordinated function of the hip, knee, and ankle, intact proprioception, and adequate muscular strength, especially the hip abductors (gluteus medius and minimus), which stabilize the pelvis during single-limb stance. A deviation in any one of these systems produces a characteristic, examinable gait pattern.

Antalgic Gait

An antalgic gait is a pain-avoidance pattern, most classically from hip, knee, or ankle pathology, or from an acutely inflamed lumbar disc or sacroiliac joint. The hallmark is a shortened stance phase on the painful side — the patient minimizes the time spent bearing weight on the affected limb, producing an asymmetric, uneven step rhythm. Trunk lean toward the painful side is also frequently observed, since shifting the body's center of gravity over a painful hip reduces the abductor muscle force (and joint reaction force) required to keep the pelvis level. Antalgic gait is a symptom-driven compensation, not a specific diagnosis — the exam expects candidates to recognize the pattern and then pursue orthopedic testing to localize the pain generator.

Trendelenburg Gait and the Trendelenburg Sign

The Trendelenburg sign tests gluteus medius (hip abductor) strength and stability. The patient stands and lifts one foot off the ground, standing only on the stance leg. A positive sign occurs when the pelvis on the raised (non-weight-bearing) side drops, because the weight-bearing side's gluteus medius is too weak to hold the pelvis level. This is frequently mis-stated on exams, so the rule to memorize is: the pelvis drops opposite the weak abductor, and weakness is named for the stance (weight-bearing) limb.

When this weakness is present during walking, it produces a Trendelenburg gait: with each step, the pelvis drops toward the swing-leg side because the stance-leg abductors cannot hold it level. Patients often compensate with a compensated Trendelenburg (lurching) gait, leaning the trunk toward the weak stance side to shift the center of gravity medially and reduce the demand on the weak abductor — this compensation can mask the pelvic drop and must be watched for separately. Causes include superior gluteal nerve injury, L5 radiculopathy, hip abductor tears, and developmental hip dysplasia.

Ataxic Gait

Ataxic gait describes incoordination during walking and has two mechanistically distinct forms that the exam distinguishes carefully:

• Cerebellar (staggering) ataxia: a wide-based, irregular, lurching gait with poor tandem-walk ability; it worsens with eyes open or closed roughly equally, since the deficit is in coordination itself, not sensory input. Associated with cerebellar lesions, alcohol intoxication, or posterior circulation stroke.
• Sensory ataxia: results from loss of proprioceptive input (posterior column disease, peripheral neuropathy, vitamin B12 deficiency, tabes dorsalis). Produces a steppage/stomping gait, with the patient watching the ground and slapping the feet down to substitute visual and auditory feedback for lost position sense. Critically, this form worsens dramatically with the eyes closed, which is the basis of the Romberg test — a positive Romberg (loss of balance with eyes closed but not open) localizes the lesion to the dorsal columns or peripheral sensory pathways rather than the cerebellum or vestibular system.

Scoliosis Screening

Screening for structural scoliosis is a standard part of the static/dynamic postural exam, particularly in adolescent patients. The primary screening tool is the Adam's forward bend test: the patient bends forward at the waist with feet together, knees straight, and arms hanging free while the examiner views the spine from behind (and sometimes from the front for lumbar curves). A positive finding is a visible rib hump or paraspinal muscle prominence on one side, because axial rotation of the vertebral bodies in structural scoliosis carries the ribs with it — a finding that is absent in simple postural asymmetry or leg-length-driven curves, which have no rotational component and therefore no rib hump.

Quantitative follow-up uses a scoliometer placed at the apex of the hump; a reading of roughly 5-7 degrees or more is generally used as a threshold for referral for radiographic evaluation (Cobb angle measurement). Standing postural screening also documents shoulder height, scapular prominence, waist crease asymmetry, and iliac crest height, all of which support, but do not replace, the Adam's test as the primary rotational screen.

Key Distinctions for the Exam

The most heavily tested discrimination points in this section are: (1) antalgic gait is driven by pain and shortens stance time on the painful side; (2) Trendelenburg gait/sign reflects hip abductor weakness, with the pelvis dropping on the side opposite the weak stance-side abductor; (3) cerebellar ataxia is vision-independent while sensory ataxia is vision-dependent (Romberg-positive); and (4) a rotational rib hump on Adam's test, not simple curve visibility, is what distinguishes structural scoliosis from postural asymmetry.