Key Clinical Formulas & Scores
6-20 scale or CR-10 scale (0-10)
6-20: 6 = no exertion, 20 = maximal exertion
Estimate of exercise intensity relative to individual's capacity
Used in cardiac rehabilitation, exercise prescription, research
Heart rate estimation: RPE × 10 ≈ %HRmax (approximate)
0 = sick leave/disability for knee problems
5 = recreational sports (cycling, cross-country skiing)
7 = competitive sports (soccer, basketball)
10 = competitive sports (football, international level)
Used to assess return-to-sport readiness after knee injuries
Comparison with Lysholm score for comprehensive knee assessment
4 activities scored 0-4 each (total 0-16):
Running, cutting, decelerating, pivoting
Score 0 = unable to perform, 4 = no difficulty
Assesses high-level knee function for return to pivoting sports
Pre-injury vs post-injury comparison valuable
5 subscales: Pain (9 items), Symptoms (7 items), ADL (17 items), Sport/Recreation (5 items), Quality of Life (4 items)
Each scored 0-100 (0 = extreme symptoms, 100 = no symptoms)
Minimal clinically important difference: 8-10 points
Used for: ACL tears, meniscal injuries, osteoarthritis, post-TKA outcomes
Sideline concussion assessment:
Symptoms (22-item scale, severity 0-6)
Cognitive assessment: orientation, immediate memory, concentration
Neurological screening: balance, gait, coordination
Delayed recall: 5-word recall
Not a standalone diagnostic tool — must be combined with clinical judgment
Red flags for cervical spine injury: dangerous mechanism, neck pain/tenderness, upper extremity numbness/tingling
Core Concepts
Concussion Management (Berlin Consensus 2017)
Definition: traumatic brain injury induced by biomechanical forces (direct or indirect force to head, neck, or body). Clinical features: headache, dizziness, confusion, amnesia, visual disturbance, balance problems, sensitivity to light/noise. Recovery: 80-90% resolve within 7-10 days (adults), longer in children/adolescents. Return-to-learn: gradual return to cognitive activity. Return-to-play (6-step): (1) symptom-limited activity, (2) light aerobic exercise, (3) sport-specific exercise, (4) non-contact training drills, (5) full-contact practice, (6) return to sport. Each step ≥24 hours, symptoms must not worsen. Never return to play on same day. Baseline testing: ImPACT neuropsychological testing.
Anterior Cruciate Ligament (ACL) Injuries
Mechanism: non-contact deceleration/pivot, valgus force with external tibial rotation. Clinical: Lachman test (most sensitive, 95%), anterior drawer, pivot shift. MRI: gold standard for diagnosis. Treatment: non-operative for partial tears, low-demand patients. Surgical reconstruction: bone-patellar tendon-bone autograft (gold standard), hamstring autograft, quadriceps tendon autograft, allograft. Rehabilitation: 9-12 months for return to sport. Graft failure rate: 2-5% (higher in adolescents). Return-to-sport criteria: ≥9 months post-op, quadriceps strength symmetry >85%, hop tests >90% limb symmetry, psychological readiness (ACL-RSI scale). Re-injury risk highest in first 12 months.
Exercise-Related Sudden Cardiac Death Screening
Causes: hypertrophic cardiomyopathy (most common in US), congenital coronary anomalies, arrhythmogenic right ventricular cardiomyopathy, myocarditis, commotio cordis, long QT syndrome. Pre-participation physical exam: history (syncope, chest pain, palpitations, family history of sudden death <50), physical exam (murmurs, blood pressure, Marfan stigmata). ECG screening: recommended by ESC for competitive athletes, not universally adopted in US (cost-effectiveness debate). Treatment of exertional syncope: complete cardiac workup before return to sport. AED availability at sporting events critical for survival of cardiac arrest.
Clinical Case Studies
Case 1: Acute ACL Tear
Patient: 22-year-old female soccer player, non-contact pivot injury with immediate "pop," rapid effusion within 2 hours. Lachman test: positive (grade III, no endpoint). Pivot shift: positive. MRI: complete ACL tear, bone bruise pattern (lateral femoral condyle + posterolateral tibia), intact menisci.
Diagnosis: Complete ACL tear (right knee).
Management: (1) Pre-operative: reduce swelling, restore full ROM (especially extension), quadriceps strengthening (prehabilitation improves post-op outcomes). (2) Surgical: ACL reconstruction with bone-patellar tendon-bone autograft (gold standard for young athletes). (3) Rehabilitation: Phase 1 (0-2 weeks): ROM, edema control, weight-bearing as tolerated. Phase 2 (2-6 weeks): progressive strengthening, closed chain exercises. Phase 3 (3-6 months): agility, plyometrics, running program. Phase 4 (6-9 months): sport-specific training. Phase 5 (9-12 months): return-to-sport testing (strength symmetry >85%, hop tests >90%, ACL-RSI >56). (4) Bracing: functional brace for return to pivoting sports (controversial, not universally recommended).
Case 2: Exercise-Associated Hyponatremia
Patient: 35-year-old female marathon runner, collapses at finish line after 4+ hours racing. Confused, nauseated, seizures × 1. Serum sodium 118 mEq/L (pre-race normal). Drank large volumes of water during race, minimal electrolyte intake. Weight gained 2 kg during race.
Diagnosis: Exercise-associated hyponatremia (EAH) — life-threatening.
Management: (1) 3% hypertonic saline 100 mL IV bolus × 1-3 doses (raises Na ~2-3 mEq/L per bolus). (2) Goal: raise Na 4-6 mEq/L within 6 hours (stop seizures, prevent cerebral edema). (3) Do NOT give free water — worsens hyponatremia. (4) Monitor Na q2-4h until >130. (5) Prevention: drink to thirst (not to a schedule), include sodium in fluid replacement for events >2 hours, avoid NSAIDs (impair free water excretion). (6) Risk factors: low body weight, female sex, NSAID use, drinking excessively, slow race time.
Case 3: Concussion in Adolescent Athlete
Patient: 16-year-old male soccer player, head-to-head collision, immediate dizziness, confusion, amnesia for event. Vomited × 1 on sideline. SCAT5: positive for concussion. No loss of consciousness. No cervical spine tenderness. Glasgow Coma Scale 14 (E4 V4 M6).
Diagnosis: Sport-related concussion (mild traumatic brain injury).
Management: (1) Same-day return to play: CONTRAINDICATED (never). (2) Physical and cognitive rest for 24-48 hours, then gradual stepwise return-to-learn protocol. (3) Graduated return-to-play (6 steps): each step ≥24 hours, no symptom recurrence. (4) Total recovery time: children/adolescents often take longer (14-28 days). (5) Cervical spine: clinical clearance (no imaging needed if no red flags). (6) Neuropsychological testing (ImPACT) when symptoms resolve for baseline comparison. (7) Education for athlete and parents about symptoms and recovery expectations. (8) Consider baseline testing for future reference.
Practice Questions
A: Marx scale ranges 0-16 (4 activities × 0-4 points). Score of 12/16 indicates high-level function — running, cutting, decelerating, and pivoting at near-normal capacity. Compare to pre-injury level for return-to-sport assessment.
A: Lachman test — performed at 20-30 degrees knee flexion with anterior tibial translation. Sensitivity 95%, specificity 90%. Anterior drawer is less sensitive (best for chronic tears). Pivot shift is most specific for functional instability but difficult to perform in acute setting.
A: Serum sodium <135 mEq/L during or within 24 hours of exercise. Severe: <125 mEq/L (neurologic symptoms, seizures, coma, death). Treatment: 3% hypertonic saline 100 mL IV bolus. Goal: raise Na 4-6 mEq/L in first 6 hours.
A: Bone-patellar tendon-bone (BPTB) autograft. Pros: bone-to-bone healing, gold standard track record, lowest graft failure rate in high-level athletes. Cons: anterior knee pain, patellar tendonitis, risk of patellar fracture. Hamstring autograft alternative with slightly higher graft failure in adolescents.
A: (1) Symptom-limited activity, (2) Light aerobic exercise, (3) Sport-specific exercise, (4) Non-contact training drills, (5) Full-contact practice, (6) Return to sport. Each step ≥24 hours. If symptoms recur, return to previous step and wait 24 hours before re-attempting.