01Approach to the Critical Patient/attcp32

Immediate priorities

›Orthopedic urgency recognition

›Complete rupture: no active knee extension, palpable suprapatellar gap

›Prompt orthopedic consultation in the ED for all suspected complete tears

›Delayed diagnosis leads to tendon retraction, more complex surgery, worse outcomes

›Bilateral rupture alarm

›May mimic spinal cord injury or Guillain-Barre syndrome

›Strongly associated with systemic metabolic disease: CKD, hyperparathyroidism, gout, diabetes

›Immediate neurovascular and metabolic assessment required

›Open extensor mechanism injury

›Open wound over tendon requires urgent operative management

›Tetanus status and antibiotic coverage

Escalation triggers

›Critical findings requiring immediate action

›Neurovascular compromise distal to injury

›Absent or diminished distal pulses

›Compartment syndrome signs: pain with passive stretch, tense compartment

›Bilateral simultaneous rupture

›Emergent metabolic workup: BMP, PTH, calcium, phosphorus

›Orthopedic consultation for both knees

›Hemodynamic instability

›Assess for associated injuries or blood loss

›Hemarthrosis rarely causes significant blood loss in isolation

Key decision points

›Complete vs partial tear determination

›Complete tear: inability to perform straight leg raise, palpable gap

›Surgical repair required, ideally within days to 2 weeks

›Orthopedic consultation before discharge

02History/hx54

Mechanism and onset

›Classic mechanism

›Sudden eccentric quadriceps contraction against a flexed knee

›Fall, stumble, or misstep (most common)

›Sports activity: landing from a jump, deadlifting

›Spontaneous rupture with minimal or no trauma

›Suggests underlying metabolic or connective tissue disorder

›Higher suspicion in dialysis patients or those on chronic steroids

Symptom characterization

›Core presenting symptoms

›Acute severe anterior knee or suprapatellar pain

›Immediate onset at moment of injury

›"Pop" or "giving way" sensation

›Inability to bear weight or walk normally

›Inability to straighten the knee

›Complete inability to perform straight leg raise in complete rupture

Prior knee and tendon history

›Relevant past musculoskeletal history

›Prior quadriceps tendinopathy or partial tears

›Prior episodes of tendon pain or stiffness

›History of tendinopathy symptoms suggesting chronic degeneration

›Previous extensor mechanism surgery or total knee arthroplasty

›Altered anatomy increases risk

›Prior contralateral tendon rupture

Risk factor history

›Systemic disease history

›Chronic kidney disease and dialysis status

›Dialysis vintage and secondary hyperparathyroidism status

03Physical Exam/exam43

Vitals and general

›Stability and general assessment

›Vital signs

›Heart rate, blood pressure, oxygen saturation

›Hemodynamic instability rare in isolated rupture

›Ability to bear weight or ambulate

›Complete rupture typically prevents normal gait

Knee inspection and palpation

›Suprapatellar region examination

›Visible suprapatellar swelling and ecchymosis

›Soft tissue defect may be visible above the patella

›Pathognomonic finding: palpable suprapatellar gap 1-2 cm above superior pole of patella

›Patella position

›Patella baja or infera: low-riding patella compared to contralateral side

›Compare patella height bilaterally

›Hemarthrosis

›Intra-articular effusion from hemarthrosis common

Functional testing

›Extensor mechanism assessment

›Straight leg raise test

›Inability to raise extended leg off the bed: complete rupture

›Hallmark finding for complete rupture

›Active knee extension against gravity

›Partial tears may allow extension with gravity eliminated but not against resistance

›Grade extension strength to characterize partial vs complete

›Active knee extension against resistance

›Complete failure: complete rupture

›Reduced strength: high-grade partial tear

04Differential Diagnosis/ddx36

Extensor mechanism injuries

›Patellar tendon rupture

›ICD-10 M66.361 (right), M66.362 (left)

›Pain and gap are infrapatellar

›Patella alta on X-ray vs patella baja in quadriceps rupture

›Patellar fracture

›ICD-10 S82.001

›Six times more common than tendon ruptures

›Direct blow mechanism, palpable crepitus, visible on X-ray

›Quadriceps strain or contusion

›ICD-10 S76.111

›Preserved though painful extension

›No palpable gap; bruising common

Bony injuries and instability

›Fractures and dislocations

›Femoral neck or shaft fracture

›ICD-10 S72.001, S72.301

›Inability to bear weight; pain with log roll; visible on X-ray

›Knee dislocation or multiligament injury

›ICD-10 S83.006

›Gross instability; assess for vascular injury

›Ankle-brachial index if knee dislocation suspected

Neurologic mimics

›Neurologic causes of extension weakness

›L3-L4 radiculopathy

›ICD-10 M54.4

›Weakness of knee extension but no palpable gap

›Positive neurologic findings; no acute trauma

05Laboratory Tests/lt30

Metabolic workup

›Renal and metabolic panel

›Basic or comprehensive metabolic panel

›Creatinine and BUN for CKD screening

›Calcium and phosphorus for secondary hyperparathyroidism assessment

›Electrolytes: hyperkalemia risk in CKD patients

›Parathyroid hormone level

›Indicated if CKD or suspected hyperparathyroidism

›Elevated iPTH associated with tendon degeneration in dialysis patients

›Alkaline phosphatase

›Elevated in secondary hyperparathyroidism

›Supports metabolic bone disease diagnosis

Inflammatory and systemic labs

›Inflammatory markers and metabolic disease

›Uric acid

›Elevated in gout: associated with tendon weakening

›HbA1c or glucose

›Diabetes mellitus screening and control assessment

›ESR and CRP

›If concern for inflammatory arthropathy or infection

›Not specific for rupture diagnosis

›Complete blood count

›Baseline; low hemoglobin seen in CKD patients

›Leukocytosis if concurrent infection suspected

Pre-operative considerations

›Surgical clearance labs

›Coagulation profile

›PT, INR if anticoagulation use or liver disease

06Diagnostic Tests/dt66

Scoring Systems

›Functional outcome scoring (post-operative use)

›Lysholm Knee Score

›Evaluates pain, instability, locking, swelling, stair climbing, squatting

›Not validated for ED diagnosis; used for post-operative outcome assessment

›International Knee Documentation Committee (IKDC) score

›Measures symptoms, function, sports activity

›Used for long-term rehabilitation monitoring

›No validated ED-specific scoring system for quadriceps tendon rupture

›Clinical triad (acute pain, palpable gap, inability to extend) is the diagnostic standard

›High clinical suspicion with low threshold for imaging is recommended

MRI

›MRI characteristics and indications

›Gold standard imaging modality

›Sensitivity, specificity, and positive predictive value of 1.0 for complete rupture

›Definitive characterization of partial vs complete tears

›Indications

›Clinical diagnosis uncertain

›Partial tear suspected: characterize extent before surgical planning

›Pre-operative planning for reconstruction type

›MRI findings in complete rupture

›Tendon discontinuity at or near the superior pole of the patella

›Tendon retraction proximal

›Fluid-filled gap in the tendon

›Bone marrow edema at insertion site

›MRI findings in partial tear

›Partial fiber disruption with intact superficial layer

›Intratendinous signal change without complete discontinuity

07Disposition/dispo36

Admission indications

›Criteria for hospital admission

›Bilateral rupture

›Metabolic optimization required prior to surgical repair

›Electrolyte abnormalities in dialysis patients

›Nephrology or endocrinology co-management needed

›Significant comorbidities requiring optimization

›Dialysis patients with acute electrolyte derangements

›Uncontrolled diabetes or cardiovascular disease requiring pre-operative optimization

›Inability to safely mobilize with appropriate support

›No support system or home assistance

›Inability to use crutches or walker safely

Discharge criteria

›Safe discharge parameters

›Confirmed or suspected partial tear with preserved extension

›Knee immobilized in extension with immobilizer

›Reliable patient with access to follow-up within 48-72 hours

›Complete tear with same-day orthopedic consultation completed

›Surgical plan established

›Patient able to mobilize safely with crutches

›Pain adequately controlled with oral medications

›Written discharge instructions provided

›Return precautions clearly explained

Consultation and follow-up

›Mandatory consultations and follow-up

›Orthopedic surgery consultation in the ED for all complete ruptures

›Urgent surgical repair is the standard of care

›Class I expert consensus recommendation

08Treatment/t69

Immediate ED management

›Analgesia

›Non-opioid first-line analgesia

›Acetaminophen 1000 mg orally every 6-8 hours

›Ibuprofen 400-600 mg orally every 6-8 hours if no contraindication

›Avoid if CKD, bleeding risk, or surgeon requests pre-operative avoidance

›Opioid analgesia for severe pain

›Morphine 2-4 mg IV every 4-6 hours as needed

›Oxycodone 5-10 mg orally every 4-6 hours as step-down

›Adjunct analgesia

›Ice pack to knee: 20 minutes on, 20 minutes off

›Elevation of affected limb

Immobilization

›Knee immobilization in full extension

›Knee immobilizer (preferred for isolated rupture)

›Immobilize in full extension 0 degrees

›Allows for easy removal for reassessment

›Long-leg posterior splint alternative

›0 degrees of extension

›Used if significant swelling or instability

›Weight-bearing restriction

›Non-weight-bearing or toe-touch weight-bearing with crutches

›Crutch instruction before discharge

Surgical repair (definitive management)

›Complete tear: surgical repair

›Timing of repair

›Ideally within days to 2 weeks of injury

›Acute repair associated with significantly better outcomes

›Delayed repair (chronic tear) requires more complex reconstruction

›Surgical techniques

›Transosseous suture repair

›Traditional gold standard technique

›Sutures passed through bone tunnels in the patella

›Suture anchor repair

›Comparable outcomes to transosseous technique

›Shorter operative time in comparative studies

›Augmentation for complex or poor-quality tissue

›V-Y plasty for lengthening in retracted chronic tears

›Allograft or autograft for mid-substance tears or revision cases

Nonoperative management

›Partial tears: nonoperative protocol

›Low-grade partial tear criteria

›Preserved active extension against gravity

›MRI confirms intact deep layer of tendon

›Immobilization protocol

›Knee immobilizer in full extension for 4-6 weeks

›Progressive weight-bearing as tolerated after 2-4 weeks

›High-grade partial tear consideration

›Often require surgical repair despite partial intact fibers

›Orthopedic decision based on functional loss and MRI grading

Post-operative rehabilitation protocol

›Rehabilitation phases

›Phase 1: 0-6 weeks post-operative

›Immediate protected weight-bearing in orthosis locked in extension

›Passive ROM initiated early to prevent stiffness

›Avoid active extension for approximately 6 weeks

›Phase 2: 6-12 weeks

›Progressive strengthening program initiated

›Active-assisted ROM exercises

›Orthosis weaned progressively

›Phase 3: 3-6 months

›Full strengthening and functional rehabilitation

›Return to sport or heavy activity

›97% return to work at long-term follow-up

›Average active flexion approximately 133 degrees at long-term follow-up

DVT prophylaxis

›Thromboprophylaxis

›VTE risk assessment

›Surgical patients: DVT rate approximately 2.5% post repair

›Immobilization increases VTE risk

›Pharmacologic prophylaxis options

›Low molecular weight heparin: enoxaparin 40 mg subcutaneous daily

›Initiated post-operatively per orthopedic surgeon direction

›Mechanical prophylaxis

›Compression stockings to contralateral leg during immobility

09Special Populations/sp47

Pregnancy

›Quadriceps tendon rupture in pregnancy

›Epidemiology in pregnancy

›Extremely rare; case reports only

›Altered biomechanics and weight gain increase extensor mechanism stress

›Imaging considerations

›Ultrasound is preferred first-line imaging: no ionizing radiation

›MRI without gadolinium acceptable if ultrasound inconclusive

›Avoid CT if possible; use only if bony injury requires exclusion

›Surgical and anesthetic considerations

›Multidisciplinary team: orthopedics, obstetrics, anesthesia

›Timing of surgical repair depends on gestational age and stability

›Regional anesthesia preferred where feasible

›Analgesia in pregnancy

›Acetaminophen: safest analgesic in all trimesters

›NSAIDs: avoid after 20 weeks gestation (risk of premature ductal closure)

›Opioids: use with caution; neonatal opioid syndrome risk with prolonged use

Geriatric

›Considerations in patients older than 65

›Epidemiology in geriatric patients

›Peak incidence age 40-70 years; majority of cases in this demographic

›Higher prevalence of comorbidities: CKD, diabetes, gout, PVD

›Increased risk of chronic tendon degeneration underlying acute rupture

›Analgesia considerations

›NSAIDs: increased risk of renal toxicity, GI bleeding, cardiovascular events

›Prefer acetaminophen as first-line

›Opioids: increased risk of delirium, falls, respiratory depression

›Reduce opioid doses by 25-50% in frail elderly patients

10Background/b55

Epidemiology

›Incidence and demographics

›Incidence approximately 1.37 per 100,000 persons per year

›Uncommon but clinically significant injury

›Less common than patellar tendon rupture

›Demographics

›Predominantly males older than 40 years

›Male predominance: approximately 80-90% of cases

›Peak incidence in the fifth and sixth decades of life

›Misdiagnosis rates

›Initial misdiagnosis rates approach 50% in some series

›High index of suspicion required in ED practice

›Bilateral rupture

›Occurs in up to 5% of cases

›Strongly associated with systemic metabolic disease

Pathophysiology

›Mechanisms of tendon failure

›Normal anatomy

›Quadriceps tendon inserts at the superior pole of the patella

›Composed of three to four layers from rectus femoris, vasti muscles

›Bears tensile loads up to 8 times body weight during dynamic activity

›Degenerative pathway

›Chronic tendinopathy with collagen disorganization precedes most ruptures

›Hypovascular zone 1-2 cm proximal to patellar insertion is most vulnerable

›Rupture typically occurs at the osteotendinous junction

›Metabolic contributors to tendon degeneration

›Secondary hyperparathyroidism: excess PTH causes collagen weakening

›Calcium pyrophosphate crystal deposition in tendons (gout, pseudogout)

11Patient Discharge Instructions/pdi29

copy discharge instructions

›Quadriceps Tendon Rupture - Discharge Instructions

›What happened to you

›You have been diagnosed with a quadriceps tendon rupture or injury

›The quadriceps tendon connects the thigh muscles to the kneecap

›This injury requires orthopedic follow-up and likely surgical repair

›Your knee brace or immobilizer

›Keep the knee immobilizer on at all times including when sleeping

›Do not attempt to bend the knee until cleared by your orthopedic surgeon

›Adjust straps for comfort but maintain full extension of the knee

›Weight-bearing and mobility

›Non-weight-bearing or toe-touch weight-bearing with crutches only

›Do not put your full weight on the affected leg

›Use crutches for all walking until seen by orthopedic surgeon

›Pain management at home

›Acetaminophen (Tylenol) 500-1000 mg every 6-8 hours as needed

›Ibuprofen 400-600 mg every 6-8 hours with food if prescribed and no kidney problems

›Ice pack 20 minutes on, 20 minutes off to the knee

›Elevate the leg above heart level when resting to reduce swelling

›Your follow-up appointment

›You must see an orthopedic surgeon within 48-72 hours (complete tear) or 1-2 weeks (partial tear)

›Delayed treatment significantly worsens surgical outcomes

›Bring your discharge paperwork and imaging results to your appointment

›Return to the emergency department immediately if

›Severe increase in pain, redness, or warmth in the knee or leg

›Calf swelling or pain (possible blood clot)

›Numbness, tingling, or color change in the foot or toes

›Fever above 38.5 degrees Celsius

12References/r27

Guidelines and key sources

›Primary clinical references

›Arnold EP, Sedgewick JA, Wortman RJ, Stamm MA, Mulcahey MK. Acute Quadriceps Tendon Rupture: Presentation, Diagnosis, and Management. JBJS Reviews. 2022. PMID 35130193

›Core review establishing incidence 1.37 per 100,000 per year and clinical triad

›Ilan DI, Tejwani N, Keschner M, Leibman M. Quadriceps Tendon Rupture. Journal of the American Academy of Orthopaedic Surgeons. 2003. PMID 12828449

›Misdiagnosis rates approaching 50%; surgical repair outcomes data

›Ciriello V, Gudipati S, Tosounidis T, Soucacos PN, Giannoudis PV. Clinical Outcomes After Repair of Quadriceps Tendon Rupture: A Systematic Review. Injury. 2012. PMID 22959496

›Systematic review of surgical outcomes: re-rupture, DVT, heterotopic ossification rates

›Pengas IP, Assiotis A, Khan W, Spalding T. Adult Native Knee Extensor Mechanism Ruptures. Injury. 2016. PMID 27423309

›Risk factors: fluoroquinolones, corticosteroids, aromatase inhibitors

Pharmacologic and metabolic references

›Drug safety and metabolic disease references

›Morales DR, Slattery J, Pacurariu A, et al. Relative and Absolute Risk of Tendon Rupture With Fluoroquinolone and Concomitant Fluoroquinolone/Corticosteroid Therapy. Clinical Drug Investigation. 2019. PMID 30465300

›aIRR of 19.36 for tendon rupture with fluoroquinolone and corticosteroid combination

›Chang CK, Chien WC, Hsu WF, et al. Positive Association Between Fluoroquinolone Exposure and Tendon Disorders. Frontiers in Pharmacology. 2022. PMID 35387340

›Population-based cohort confirming fluoroquinolone tendon injury risk

›Wu W, Wang C, Ruan J, et al. Simultaneous Spontaneous Bilateral Quadriceps Tendon Rupture With Secondary Hyperparathyroidism in a Patient Receiving Hemodialysis. Medicine. 2019. PMID 30855501

›Bilateral rupture mechanism in CKD with hyperparathyroidism

›Malta LM, Gameiro VS, Sampaio EA, Gouveia ME, Lugon JR. Quadriceps Tendon Rupture in Maintenance Haemodialysis Patients. Injury. 2014. PMID 25441174

›Risk factor analysis and surgical outcomes in dialysis patients

Surgical technique references

›Operative technique and outcome studies

›Jammal M, Weil Y, Kanaann M, Mosheiff R, Oulianski M. Comparative Outcomes of Trans-Osseous Tunnels Versus Suture Anchors for Acute Quadriceps Tendon Rupture. Injury. 2026. PMID 41724016

›Comparable outcomes between transosseous and suture anchor repair techniques

›Danaher M, Faucett SC, Endres NK, Geeslin AG. Repair of Quadriceps and Patellar Tendon Tears. Arthroscopy. 2023. PMID 36332853

›Augmentation strategies for complex and chronic tears

›Boudissa M, Roudet A, Rubens-Duval B, Chaussard C, Saragaglia D. Acute Quadriceps Tendon Ruptures: A Series of 50 Knees With Average Follow-Up More Than 6 Years. OTSR. 2014. PMID 24529850

›Long-term outcomes: average active flexion 133 degrees; 97% return to work

Evidence & Review

Evidence & Review