Medical Calculators for Physical Therapists

FRAX estimates 10-year probability of major osteoporotic fracture (hip, spine, wrist, shoulder) using clinical risk factors with or without bone mineral density (BMD). Physical therapists use FRAX to identify patients who may benefit from falls prevention programs, balance training, and strength exercise, and to guide referral for DEXA scanning or pharmacological treatment. Intervention thresholds vary by country — in the US, treatment is generally considered when 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20% (NOF guidelines).

The Ottawa Ankle Rules determine whether ankle X-ray is needed after injury. X-ray is indicated if: bone tenderness at the posterior edge or tip of the lateral malleolus OR medial malleolus, OR inability to weight-bear (4 steps) immediately after injury and in the ED. Sensitivity is ~98% for fracture, allowing safe rule-out when negative. PTs applying these rules in sports medicine or community settings should confirm the patient was assessed within 10 days of injury and has no findings that exclude the rule (e.g., isolated midfoot injury, which uses Ottawa Foot Rules instead).

VO2 max (maximal oxygen uptake) measures cardiorespiratory fitness. Field estimates (Cooper 12-minute run, Rockport walk test) are used when formal lab testing is unavailable. In cardiac rehabilitation, VO2 max determines exercise prescription intensity and tracks functional improvement. In pulmonary rehab (COPD), VO2 max informs the BODE index and predicts survival. For healthy adults, VO2 max <25 mL/kg/min indicates poor fitness; ≥50 mL/kg/min is excellent. Exercise training typically improves VO2 max by 10–30% over 8–12 weeks.

The modified Medical Research Council (mMRC) dyspnea scale grades breathlessness: 0 = dyspnea only with strenuous exercise; 1 = when hurrying or walking up a slight hill; 2 = walks slower than peers or stops after 15 minutes on the level; 3 = stops after 100 yards or a few minutes; 4 = too breathless to leave the house. mMRC ≥2 is a criterion for COPD GOLD group B/D assessment and pulmonary rehab referral. In pulmonary rehab, mMRC is tracked alongside 6-minute walk distance and SGRQ to measure functional outcomes.

Heart rate zones are calculated from maximum HR (HRmax = 220 − age, or measured directly). Zones: Zone 1 (50–60% HRmax) = very light, active recovery; Zone 2 (60–70%) = light, fat oxidation, aerobic base; Zone 3 (70–80%) = moderate, aerobic conditioning; Zone 4 (80–90%) = hard, lactate threshold; Zone 5 (90–100%) = maximum effort. For cardiac rehab, the Karvonen formula (target HR = [(HRmax − HRrest) × intensity%] + HRrest) is preferred as it accounts for resting HR. Initial cardiac rehab typically targets 40–70% heart rate reserve.

ECOG performance status (0–5) quantifies functional capacity, which directly informs rehabilitation goals and intensity for oncology patients. ECOG 0–1: standard exercise prescription, focus on fitness maintenance and fatigue management. ECOG 2: modified exercise program, prioritize ADL function and symptom management. ECOG 3: low-intensity mobility and strength work, focus on preventing deconditioning and maintaining independence. ECOG 4: passive range of motion, positioning, and caregiver education. Exercise oncology evidence supports rehabilitation across all ECOG levels — even ECOG 3–4 patients benefit from adapted activity.