Measurement Principles and ROM Assessment Lecture

Rationale for Precise Measurement

• Getting it right the first time safeguards patient diagnosis, treatment plans, and research data integrity.

• Measurements are used to:

  • Track change in function, evaluate intervention success.

  • Compare to norms (while acknowledging individual variability).

• Ethical / practical stakes: a faulty diagnosis ⇒ sub-optimal or harmful care.

• Goal: produce data that could withstand research‐level scrutiny, even in routine clinical practice.

Sources of Variability & Error

• User-related: improper tool use or interpretation.

• Patient-related: sex, age, activity, body habitus, mood, comorbidities.

• Instrument-related: calibration, build quality (e.g., mis-printed STAR mats).

• Environment / protocol: footwear differences, unclear instructions.

Variable Types (Data Language)

• Quantitative (height, weight, girth) – continuous.

• Qualitative/descriptive – can be coded numerically (e.g., sex: 0 = female, 1 = male).

• Continuous vs discrete examples:

  • Continuous: height (no upper bound).

  • Discrete: pain scale 0-10, dead/alive, pregnant/not.

Reliability – Consistency of Measurement

• Desired formula: \text{Observation}=\text{True Value}\pm\text{Error} (minimise error).

• Error Types:

  • Systematic: consistent but wrong (uncalibrated scale, fast alarm clock). Reliable ⟂ valid.

  • Random: unpredictable influences (caffeine before BP, depression on pain scale).

• Levels of reliability:

  • Test–retest (same tool, different times).

  • Intra-rater (same examiner).

  • Inter-rater (different examiners).

  • Alternate-forms (different tools).

  • Internal consistency (variance within a tool/battery).

• Always pilot-test protocols & instruments before formal data collection.

Validity – Are We Measuring the Intended Construct?

• Accurate ≠ merely consistent.

• Bullseye analogy:

  • Tight cluster off-centre ⇒ reliable but invalid.

  • Scattered hits ⇒ unreliable & invalid.

  • Tight on centre ⇒ reliable & valid (ideal).

• Questionnaire examples:

  • FAAM: higher score = better function.

  • IDFAI: higher score = more pathology (threshold for chronic ankle instability). Know directionality!

• Range-of-motion example: “more” ROM isn’t automatically good (hypermobility may equal instability).

Foundational Biomechanics

• Cardinal planes: sagittal, coronal, transverse.

• Axes of rotation: mediolateral, anteroposterior, superoinferior (each ⟂ its plane).

• Osteokinematics (visible joint motion) vs arthrokinematics (roll, glide, spin).

Range-of-Motion Terminology

• Zero–180° notation; always start at anatomical zero.

• Categories:

  • AROM – patient moves actively.

  • PROM – clinician moves relaxed limb.

  • RROM – resisted (strength test).

  • AAROM – active-assist (rehab, not eval).

• Normal end-feels (asymptomatic):

  • Soft (tissue approximation).

  • Firm (muscle/ligament stretch).

  • Hard (bony block – e.g., olecranon fossa).

• Pathological end-feels:

  • Boggy soft (swelling).

  • Abnormally firm (adhesions, spasm).

  • Hard (loose body, meniscus tear).

  • Empty (ligament rupture – no restraint).

Goniometry Essentials

• Parts: stationary/proximal arm (with dial), moving/distal arm, axis/pivot.

• Tool options: 360° plastic, half-circle, finger goniometers, inclinometers, electro-goniometers.

• Set-up principles:

  • Identify bony landmarks (axis, proximal alignment, distal alignment).

  • Stabilise proximal segment; remove obstacles.

  • Stationary arm must remain fixed; moving arm stays parallel to distal segment.

• Recording example:

  • “R ankle PF AROM 0°-50°, pain-free, muscular end-feel.”

• Three-point notation for hyper-extension:

  • Knee: 5°-0°-135° (5° hyperextension through 135° flexion).

ROM Joints & Motions to Master

Lower extremity

• Hip (femoroacetabular): flex-ext, ABD-ADD, IR-ER.

• Knee (tibiofemoral).

• Ankle: talocrural (DF/PF) + subtalar (INV/EV) → combine for pronation/supination.
  Upper extremity

• Shoulder (glenohumeral): flex, ext, ABD, ADD, IR, ER, horizontal ABD/ADD.

• Elbow: flex/ext; forearm pron-sup (radioulnar).

• Wrist & hand: radiocarpal, DRUJ, MCP/PIP/DIP, thumb CMC/IP.

Program‐Standard “Normal” ROM Values (memorise)

• Hip Flex 120°, Ext 20°; ABD 45°, ADD 30°; IR/ER 45°.

• Knee Flex 135°, Ext 0° (hyperextension recorded separately).

• Ankle PF 50°, DF 20°; Inversion 35°, Eversion 15°.

• Shoulder Flex 180°, Ext 60°, ABD 180°, IR 70°, ER 90°, Hor ABD 45°, Hor ADD 135° (*added by instructor).

• Elbow Flex 150°, Ext 0°; Forearm Pronation 80°, Supination 80°.

• Wrist Flex 80°, Ext 70°; Rad Dev 20°, Uln Dev 30°.

Manual Muscle Testing (MMT)

Purpose & Context

• Quick, cheap assessment of strength; good intra-rater reliability with practice.

• Distinguish from manual resistance exercises (rehab modality) – intent differs.

Tools & Alternatives

• Classic MMT (5-point scale).

• Handheld dynamometer (objective Newton/kg/lb readings, brake or make tests).

• Isokinetic dynamometers (Biodex, KinCom) – research/advanced clinic.

Testing Principles

• Stabilise proximal segment; apply resistance distally & gradually.

• Use antigravity positions unless too weak (then gravity-minimised plane).

• One-joint muscle: test at end-range; two-joint: mid-range.

• Order logically: supine → prone → sitting → standing to minimise patient repositioning.

• Watch for substitutions & “cogwheel” guarding (malingering/kinesiophobia).

MMT 0-5 Grading Scale

Documentation Tips

• Always include: limb, motion, AROM/PROM/RROM, starting/ending angles, pain or other symptoms, end-feel, limiting factors (e.g., body habitus), patient comments.

• Note footwear or equipment conditions (e.g., STAR test barefoot). Establish & follow Standard Operating Procedures.

Clinical & Research Implications

• Consistency → reduced error → clearer clinical decision-making and stronger research conclusions.

• Pilot practice for both people & devices before collecting “real” data.

• Understand scoring direction and normal ranges before interpreting a metric.

• Biopsychosocial lens: mood, fear, motivation can alter both ROM and strength scores.

Key Take-Home Messages

• Reliable ≠ valid; you must strive for both.

• Systematic practice, proper landmarks, and rigorous SOPs are non-negotiable.

• Record hyperextension with three-point notation.

• Memorise program-adopted ROM norms; cite deviations explicitly.

• Use MMT scale accurately; know difference between brake & make tests.

• Every measurement decision (tool, position, wording) has downstream effects on patient care and research quality.