Statics and dynamics: visual criteria of the musculoskeletal system

Visual examination remains the starting point: it is quick, non-invasive, and often informative enough to identify key movement patterns and hypothesize dysfunction. But it is important to remember: there is no single "ideal standard posture" for everyone, and common tools like the Kendall plumb line should be interpreted with caution and tied to symptoms and function, not to a "poster ideal." Contemporary reviews emphasize that "standard posture" as a goal is a myth; the variability of the norm is significant. [1]

To make visual assessment more objective, validated metrics and scales are used: craniovertebral angle (assessment of head protrusion), Foot Posture Index (FPI-6) for the foot, structured observation of the scapula during shoulder movements, and, for dynamics, well-described phases of the gait cycle and functional tests (e.g., Timed Up and Go). These instruments have published norms/threshold values and acceptable reliability when used correctly. [2]

Where visual inspection is insufficient, photo/videogrammetry is used: today, even a smartphone, when protocol is followed, provides high repeatability of head angles, kyphosis/lordosis, and knee hyperextension. Recent studies demonstrate good inter-repeat reliability of photogrammetry for a number of postural parameters. [3]

Finally, when assessing dynamics, they focus on the percentage ratios of gait phases (support ~60%, swing ~40%) and key event points (heel contact, transfer, push-off). This provides a general "coordinate grid" on which deviations are visible: phase asymmetry, the absence of certain events, and disruption of sequence. [4]

Table 1. Principles of visual assessment: “fair play” with reality

Principle	What does this mean in practice?
There is no universal “ideal” posture	We compare with the functional task and symptoms, not with the poster
We use validated angles/scales	CVA for the head, FPI-6 for the foot, structural tests for the scapula
If possible, we document it on camera.	Photos/videos increase reliability and allow you to track the dynamics
Dynamics requires "beacons"	We use step phases, key events, and control tests
Any find ↔ function	We check whether correction of the finding changes pain/task performance
[5]

Statics: How to look from head to toe and what to record

Head and neck

The craniovertebral angle (CVA) is the angle between the line from the external auditory canal to the spinous process of C7 and the horizontal. Average values in healthy adults are approximately 49-50°, with a natural decrease of approximately 1.5-2° per decade and slight gender differences. Smaller angles correspond to greater forward protrusion of the head. Clinicians find it convenient to track individual CVA dynamics over time. [6]

Shoulder girdle and scapula

When raising the arm, the scapula should rotate upward, tilt backward, and rotate outward. Observation from behind in the frontal/sagittal planes and under light load helps identify scapular dyskinesia. A simple clinical visual observation test (McClure/Kibler) shows satisfactory clinical reliability in at-risk groups. [7]

Pelvis and frontal plane

We note the horizontal alignment of the iliac crests, the symmetry of the waist triangles, the position of the patellas, and the axis of the tibia. Asymmetry at rest is always compared with dynamic asymmetry (for example, during a one-legged squat).

Foot and ankle

The Foot Posture Index (FPI-6) is a rapid clinical scale (-12 to +12), where negative values correspond to supination and positive values to pronation. The method has been validated and has high inter-rater and repeat reliability, including in patients with low back pain. [8]

Table 2. Mini-posture protocol: landmarks in three planes

Plane	Landmarks/Angles	What to write down
Sagittal (profile)	CVA (head), thoracic kyphosis, pelvic tilt, knee hyperextension	Numbers/rating + photo
Frontal (back/front)	Shoulder/pelvic level, scapular medialization, patellar axis, foot arch	Symmetry/asymmetry
Transverse	Shoulder/pelvic rotation, foot rotation	Deviations when stepping from a place
Foot	FPI-6 (-12…+12)	Total for each foot
[9]

Dynamics: The basic anatomy of a step and what can go wrong

The gait cycle is divided into a support phase (~60%) and a swing phase (~40%). The support phase includes: initial contact → load response → midstance → terminal support → prestance. The swing phase: early → mid → late swing. Normally, the sequence of events and the duration of the phases are reproducible; phase asymmetry and the absence of characteristic events (e.g., "heel does not touch the ground," "no hip extension before push-off") are key visual markers. [10]

At the segment level, they look for “tricking”:

• pelvis - excessive frontal work (valgus roll),
• knee - knee mediation during squatting/support,
• foot - early overpronation or rigid supination pattern.

Pelvis-hip-knee-foot alignment in the mid-base is the foundation for an economical step. [11]

Table 3. Step phases and visual analysis cues

Phase	What should happen	What's alarming
Initial contact	Heel/full foot contact, knee slightly bent	Constant toe-strike, soft foot collapse
Response to load	Cushioning, controlled pronation	Sharp medialization of the knee, "collapse" of the pelvis
Middle support	The center of gravity is over the foot, the knee is in extension	Lack of hip extension, pelvis "sags"
Terminal support	Push, heel comes off	Early external rotation of the foot/pain bypass
Pre-transfer → max	Efficient transfer, toe clearance	Toe hooks, high hip lift
[12]

Functional tests: fast, simple, reliable

Single-Leg Squat (SLS) is the "golden" frontal plane screening tool. It reliably detects dynamic knee valgus (the knee moves medially relative to the foot) in 2D/3D imaging; inter-repeat reliability and agreement with 3D are high in protocols with fixed angles (45-60°). [13]

The Kibler/McClure scapula examination is a simple visual test of dyskinesia that is reasonably reliable in athletes at risk for overuse. It complements the shoulder girdle examination. [14]

The Timed Up and Go (TUG) is a universal assessment of mobility: stand up from a chair, walk 3 m, turn around, return, and sit down. The test is reliable and valid, and a cutoff of approximately 13.5 seconds is often used in older adults as a marker of increased fall risk (context and population are important; the TUG is part of a battery, not the sole arbiter). [15]

Table 4. Quick set of functional tests

Test	What are we looking for?	How to fix
Single-Leg Squat (SLS)	Dynamic valgus, pelvic displacement	Frontal/lateral video, marks on the patella/kneecap/2nd finger
Scapula arm lift	Wingedness, rotational delay, asymmetry	Back/side view, light dumbbell as indicated
TUG (3 m)	Time, smoothness, manual assistance	Stopwatch, repeat 2-3 times, best result
Step-down	Knee/pelvis control during descent	Frontal video, error count
Tandem stand/walk	Balance, myelopathic "failures"	Step hold time/error
[16]

Reliability and validity: what can be "believed with the eyes"

Photogrammetry (correct markings, fixed camera distance/height) shows high repeatability for CVA, sway-back and knee hyperextension; suitable for monitoring. [17]

The FPI-6 has excellent inter-rater and repeat reliability and has been shown to be reproducible even in people with low back pain.[18]

Scapular tests have acceptable clinical reliability, but diagnostic yield increases with the combination of pain/strength deficit and overhead tasks. The modified LSST can be reproducible, but its clinical utility is limited; observation in motion is preferred. [19]

SLS-valgus - 2D assessment agrees well with 3D in standardized protocols. TUG is one of the most valid "general mobility" tests, with a confirmed association with fall risk in the elderly (threshold 13.5 s from the original Shumway-Cook work). [20]

Table 5. “Green” and “yellow” zones of confidence in visual tests

Tool	You can rely on it	Comment
CVA (photo/video)	Yes, for monitoring	Follow the shooting technique
FPI-6	Yes, screening/monitoring	Assess both feet separately
Observing the scapula	Yes, as part of the battery	Better in conjunction with strength/symptoms
SLS (dynamic hallux valgus)	Yes, with the standard	Mark the angle, depth, errors
TUG	Yes, especially in older people	The threshold of 13.5 seconds is a guideline, not a death sentence.
[21]

From "picture" to plan: how to connect the static and dynamic

A visual finding is valuable when its correction improves task performance. Examples:

• arch support with the insole in a “highly pronated” foot reduces knee collapse in SLS;
• tactile cue "scapula down-back" eliminates "winging" during overhead press;
• The behavioral cue "pull the crown of your head" increases CVA and reduces neck muscle fatigue during computer work.

The logic of the modern approach is the diagnosis of the movement system: formulating the problem in terms of “functions” rather than “vertebral/muscular defects.” The position of professional societies (APTA) calls for the use of movement diagnoses and coherent intervention plans. [22]

Table 6. Template for forming a “motor diagnosis”

Observation	Functional deficit	Hypothesis about the cause	Correction test	Solution
CVA ↓, neck fatigue	Discomfort when working on a PC	Deep neck flexors are lagging behind	Chin-tuck, biofeedback → better?	Enable DSSH + pose timeouts
Scapular dyskinesia	Pain above the head	Lower trapezius/serratus deficiency	The "scapula down and back" hint	Scapular rotation exercises
FPI-6 high	SLS: knee valgus	Lack of hip/foot control	Arch support + hip abduction	Insole + hip/foot training
TUG >13.5 s	Fear of falling	Balance/strength ↓	Strength/Balance Program	Training + TUG refresher
[23]

Security and surveillance red flags

Visual assessment should be stopped and passed on to diagnostics if you see signs of neurological deficit, significant asymmetry, progressive weakness, signs of myelopathy (unsteady gait, abnormal reflexes), or obvious pain with little exertion. In the elderly, particular attention should be paid to the history of falls: in this case, TUG and other tests are not just a screening tool, but a starting point for routing. [24]

Table 7. Red flags in visual screening

Sign	What could be behind it?	Action
Severe asymmetry, progression of weakness	Neurological deficit/compression	Urgent consultation, MRI if necessary
"Dips" in tandem walking, spasticity	Myelopathy	Referral to a specialist
Pain with little exertion, swelling, redness	Trauma/inflammation	Exclude non-osseous and osseous pathology
History of falls, TUG ≥13.5 s	Increased risk of falls	Route to the Balance/Strength Program
[25]

Documentation and communication: do what colleagues and the patient will understand

In the card, record what and how you looked (postures, planes, camera distance), what scales/angles you used (CVA, FPI-6, SLS errors, TUG), what motor diagnosis you made, and what correction immediately improved task performance. Store photos/videos with metadata (date, camera distance/height) to evaluate progress during follow-up visits.

Table 8. One visit - one data table (template)

Metrics	To	After correction	Comment
CVA, °	44	50 (after the hint)	Fatigue has decreased
FPI-6 (L/R)	+8 / +7	+6 / +5 (with insole)	Symmetry +
SLS errors (L/R)	3 / 2	1 / 1 (hip training)	The knee is stable
TUG, with	15.2	12.8 (after 6 weeks)	Risk of falls ↓
[26]

Short answers to frequently asked questions

Should everyone's posture be "straightened" to the point of being on display?
No. Our goal is function and well-being. "Perfect" posture doesn't exist for everyone; we improve what interferes with the patient's goal. [27]

What angles and scales are the most useful without equipment?
CVA (head), FPI-6 (foot), scapula checklist, SLS, TUG. All have publications on validity/reliability and clear protocols. [28]

How can you quickly describe a stride without sensors?
Note whether there's heel contact, how the load response is, whether the knee is medially displaced in midstance, whether there's normal hip extension and toe clearance. Remember the phase ratio of ~60/40. [29]

Can you rely on a "visual eye" without video?
Better yet, no. A camera increases reliability, and photogrammetry demonstrates high repeatability with standard shooting. [30]