Unhappy triad
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Unhappy triad
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Anatomy clinical correlates: Spinal cord pathways
Anatomy clinical correlates: Bones, fascia and muscles of the neck
Anatomy of the oral cavity
Anatomy of the temporomandibular joint and muscles of mastication
Muscles of the face and scalp
Anatomy of the salivary glands
Nerves and vessels of the face and scalp
Anatomy of the tongue
Anatomy of the pterygopalatine (sphenopalatine) fossa
Anatomy of the inner ear
Anatomy of the infratemporal fossa
Anatomy clinical correlates: Skull, face and scalp
Anatomy of the cerebral cortex
Anatomy of the cerebellum
Anatomy of the cranial meninges and dural venous sinuses
Anatomy of the brainstem
Anatomy of the basal ganglia
Anatomy of the white matter tracts
Anatomy of the limbic system
Anatomy of the blood supply to the brain
Anatomy of the diencephalon
Anatomy of the ventricular system
Anatomy clinical correlates: Cerebral hemispheres
Anatomy of the olfactory (CN I) and optic (CN II) nerves
Anatomy of the oculomotor (CN III), trochlear (CN IV) and abducens (CN VI) nerves
Anatomy of the trigeminal nerve (CN V)
Anatomy of the facial nerve (CN VII)
Anatomy of the glossopharyngeal nerve (CN IX)
Anatomy of the spinal accessory (CN XI) and hypoglossal (CN XII) nerves
Anatomy of the vagus nerve (CN X)
Anatomy clinical correlates: Facial (CN VII) and vestibulocochlear (CN VIII) nerves
Glycolysis
Citric acid cycle
Electron transport chain and oxidative phosphorylation
Gluconeogenesis
Glycogen metabolism
Pentose phosphate pathway
Amino acid metabolism
Nitrogen and urea cycle
Fatty acid synthesis
Fatty acid oxidation
Ketone body metabolism
Cholesterol metabolism
Type I and type II errors
Sensitivity and specificity
Incidence and prevalence
Positive and negative predictive value
Test precision and accuracy
Relative and absolute risk
Odds ratio
Attributable risk (AR)
Mortality rates and case-fatality
DALY and QALY
Direct standardization
Indirect standardization
Study designs
Ecologic study
Cross sectional study
Case-control study
Cohort study
Randomized control trial
Clinical trials
Sample size
Placebo effect and masking
Disease causality
Selection bias
Information bias
Confounding
Interaction
Bias in interpreting results of clinical studies
Bias in performing clinical studies
Modes of infectious disease transmission
Vaccination and herd immunity
Prevention
Leukodystrophy
Adrenoleukodystrophy (NORD)
Zellweger spectrum disorders (NORD)
Primary ciliary dyskinesia
Alport syndrome
Ehlers-Danlos syndrome
Osteogenesis imperfecta
Marfan syndrome
Vitamin C deficiency
Peroxisomal disorders: Pathology review
Nuclear structure
DNA structure
Transcription of DNA
Translation of mRNA
Gene regulation
Epigenetics
Amino acids and protein folding
Protein structure and synthesis
Nucleotide metabolism
DNA replication
Lac operon
DNA damage and repair
Cell cycle
Mitosis and meiosis
DNA mutations
Development of the cardiovascular system
Fetal circulation
Development of the face and palate
Pharyngeal arches, pouches, and clefts
Development of the ear
Development of the eye
Development of the digestive system and body cavities
Development of the gastrointestinal system
Development of the teeth
Development of the tongue
Development of the integumentary system
Development of the axial skeleton
Development of the limbs
Development of the muscular system
Development of the nervous system
Development of the renal system
Development of the reproductive system
Development of the respiratory system
Human development days 1-4
Human development days 4-7
Human development week 2
Human development week 3
Ectoderm
Mesoderm
Endoderm
Development of the placenta
Development of the fetal membranes
Development of twins
Hedgehog signaling pathway
Development of the umbilical cord
Mendelian genetics and punnett squares
Hardy-Weinberg equilibrium
Inheritance patterns
Independent assortment of genes and linkage
Evolution and natural selection
Lesch-Nyhan syndrome
Orotic aciduria
Adenosine deaminase deficiency
Xeroderma pigmentosum
McCune-Albright syndrome
Acute radiation syndrome
Purine and pyrimidine synthesis and metabolism disorders: Pathology review
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fragile X syndrome
Huntington disease
Myotonic dystrophy
Friedreich ataxia
Turner syndrome
Klinefelter syndrome
Prader-Willi syndrome
Angelman syndrome
Beckwith-Wiedemann syndrome
Cri du chat syndrome
Williams syndrome
Alagille syndrome (NORD)
Achondroplasia
Polycystic kidney disease
Familial adenomatous polyposis
Familial hypercholesterolemia
Multiple endocrine neoplasia
Neurofibromatosis
Tuberous sclerosis
von Hippel-Lindau disease
Albinism
Cystic fibrosis
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Hemochromatosis
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Krabbe disease
Niemann-Pick disease types A and B (NORD)
Niemann-Pick disease type C
Phenylketonuria (NORD)
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Alpha-thalassemia
Beta-thalassemia
Wilson disease
X-linked agammaglobulinemia
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hemophilia
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Muscular dystrophy
Wiskott-Aldrich syndrome
Mitochondrial myopathy
Muscular dystrophies and mitochondrial myopathies: Pathology review
Miscellaneous genetic disorders: Pathology review
Blood histology
Bacterial structure and functions
Staphylococcus epidermidis
Staphylococcus aureus
Staphylococcus saprophyticus
Streptococcus viridans
Streptococcus pneumoniae
Streptococcus pyogenes (Group A Strep)
Streptococcus agalactiae (Group B Strep)
Enterococcus
Clostridium perfringens
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Bacillus cereus (Food poisoning)
Listeria monocytogenes
Corynebacterium diphtheriae (Diphtheria)
Nocardia
Actinomyces israelii
Escherichia coli
Salmonella (non-typhoidal)
Salmonella typhi (typhoid fever)
Pseudomonas aeruginosa
Enterobacter
Klebsiella pneumoniae
Shigella
Proteus mirabilis
Yersinia enterocolitica
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Serratia marcescens
Bacteroides fragilis
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Helicobacter pylori
Campylobacter jejuni
Neisseria meningitidis
Neisseria gonorrhoeae
Moraxella catarrhalis
Francisella tularensis (Tularemia)
Bordetella pertussis (Whooping cough)
Brucella
Haemophilus influenzae
Haemophilus ducreyi (Chancroid)
Pasteurella multocida
Mycobacterium tuberculosis (Tuberculosis)
Mycobacterium leprae
Mycobacterium avium complex (NORD)
Mycoplasma pneumoniae
Chlamydia pneumoniae
Chlamydia trachomatis
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Leptospira
Treponema pallidum (Syphilis)
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Gardnerella vaginalis (Bacterial vaginosis)
Varicella zoster virus
Cytomegalovirus
Epstein-Barr virus (Infectious mononucleosis)
Human herpesvirus 8 (Kaposi sarcoma)
Herpes simplex virus
Human herpesvirus 6 (Roseola)
Adenovirus
Parvovirus B19
Human papillomavirus
Poxvirus (Smallpox and Molluscum contagiosum)
BK virus (Hemorrhagic cystitis)
JC virus (Progressive multifocal leukoencephalopathy)
Poliovirus
Coxsackievirus
Rhinovirus
Hepatitis A and Hepatitis E virus
Hepatitis D virus
Influenza virus
Mumps virus
Measles virus
Respiratory syncytial virus
Human parainfluenza viruses
Dengue virus
Yellow fever virus
Zika virus
Hepatitis C virus
West Nile virus
Norovirus
Rotavirus
Coronaviruses
HIV (AIDS)
Human T-lymphotropic virus
Ebola virus
Rabies virus
Rubella virus
Eastern and Western equine encephalitis virus
Lymphocytic choriomeningitis virus
Hantavirus
Coccidioidomycosis and paracoccidioidomycosis
Histoplasmosis
Blastomycosis
Toxoplasma gondii (Toxoplasmosis)
Trichomonas vaginalis
Protein synthesis inhibitors: Aminoglycosides
Antimetabolites: Sulfonamides and trimethoprim
Antituberculosis medications
Miscellaneous cell wall synthesis inhibitors
Protein synthesis inhibitors: Tetracyclines
Cell wall synthesis inhibitors: Penicillins
Miscellaneous protein synthesis inhibitors
Cell wall synthesis inhibitors: Cephalosporins
DNA synthesis inhibitors: Metronidazole
DNA synthesis inhibitors: Fluoroquinolones
Mechanisms of antibiotic resistance
Integrase and entry inhibitors
Nucleoside reverse transcriptase inhibitors (NRTIs)
Protease inhibitors
Hepatitis medications
Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
Neuraminidase inhibitors
Herpesvirus medications
Azoles
Echinocandins
Miscellaneous antifungal medications
Anthelmintic medications
Antimalarials
Anti-mite and louse medications
Free radicals and cellular injury
Necrosis and apoptosis
Ischemia
Hypoxia
Amyloidosis
Inflammation
Wound healing
Arterial disease
Angina pectoris
Stable angina
Unstable angina
Myocardial infarction
Prinzmetal angina
Coronary steal syndrome
Peripheral artery disease
Subclavian steal syndrome
Aortic dissection
Vasculitis
Behcet's disease
Kawasaki disease
Hypertension
Hypertensive emergency
Renal artery stenosis
Coarctation of the aorta
Cushing syndrome
Conn syndrome
Hypotension
Orthostatic hypotension
Hypertriglyceridemia
Hyperlipidemia
Chronic venous insufficiency
Thrombophlebitis
Deep vein thrombosis
Lymphedema
Lymphangioma
Shock
Vascular tumors
Angiosarcomas
Candida
Tetralogy of Fallot
Truncus arteriosus
Transposition of the great vessels
Total anomalous pulmonary venous return
Hypoplastic left heart syndrome
Patent ductus arteriosus
Ventricular septal defect
Atrial septal defect
Atrial flutter
Atrial fibrillation
Premature atrial contraction
Atrioventricular nodal reentrant tachycardia (AVNRT)
Wolff-Parkinson-White syndrome
Ventricular tachycardia
Brugada syndrome
Premature ventricular contraction
Long QT syndrome and Torsade de pointes
Ventricular fibrillation
Atrioventricular block
Bundle branch block
Pulseless electrical activity
Heart failure
Cor pulmonale
Endocarditis
Myocarditis
Rheumatic heart disease
Hypertension: Pathology review
Hyperthyroidism
Diabetes mellitus
Diabetic retinopathy
Diabetic nephropathy
Hyperparathyroidism
Hypoparathyroidism
Hypercalcemia
Hypocalcemia
Hypopituitarism
Cataract
Glaucoma
Vertigo
Acyanotic congenital heart defects: Pathology review
Cyanotic congenital heart defects: Pathology review
Atherosclerosis and arteriosclerosis: Pathology review
Coronary artery disease: Pathology review
Peripheral artery disease: Pathology review
Valvular heart disease: Pathology review
Cardiomyopathies: Pathology review
Heart failure: Pathology review
Supraventricular arrhythmias: Pathology review
Ventricular arrhythmias: Pathology review
Heart blocks: Pathology review
Aortic dissections and aneurysms: Pathology review
Pericardial disease: Pathology review
Endocarditis: Pathology review
Shock: Pathology review
Vasculitis: Pathology review
Cardiac and vascular tumors: Pathology review
Dyslipidemias: Pathology review
Thyroglossal duct cyst
Hyperaldosteronism
Nasal, oral and pharyngeal diseases: Pathology review
Cleft lip and palate
Congenital diaphragmatic hernia
Esophageal web
Tracheoesophageal fistula
Pyloric stenosis
Sialadenitis
Parotitis
Oral candidiasis
Ludwig angina
Aphthous ulcers
Temporomandibular joint dysfunction
Dental abscess
Gingivitis and periodontitis
Dental caries disease
Oral cancer
Warthin tumor
Barrett esophagus
Achalasia
Plummer-Vinson syndrome
Mallory-Weiss syndrome
Boerhaave syndrome
Gastroesophageal reflux disease (GERD)
Zenker diverticulum
Diffuse esophageal spasm
Esophageal cancer
Eosinophilic esophagitis (NORD)
Gastric dumping syndrome
Peptic ulcer
Cyclic vomiting syndrome
Gastroenteritis
Gastric cancer
Gastritis
Meckel diverticulum
Celiac disease
Crohn disease
Ulcerative colitis
Hemorrhoid
Crigler-Najjar syndrome
Biliary atresia
Gilbert's syndrome
Dubin-Johnson syndrome
Rotor syndrome
Jaundice
Cirrhosis
Portal hypertension
Hepatic encephalopathy
Budd-Chiari syndrome
Non-alcoholic fatty liver disease
Cholestatic liver disease
Hepatocellular adenoma
Autoimmune hepatitis
Alcohol-induced liver disease
Alpha 1-antitrypsin deficiency
Primary biliary cirrhosis
Primary sclerosing cholangitis
Hepatitis
Neonatal hepatitis
Reye syndrome
Benign liver tumors
Hepatocellular carcinoma
Gallstones
Biliary colic
Acute cholecystitis
Ascending cholangitis
Chronic cholecystitis
Gallstone ileus
Gallbladder cancer
Cholangiocarcinoma
Acute pancreatitis
Pancreatic pseudocyst
Chronic pancreatitis
Pancreatic cancer
Pancreatic neuroendocrine neoplasms
Zollinger-Ellison syndrome
Congenital gastrointestinal disorders: Pathology review
Esophageal disorders: Pathology review
GERD, peptic ulcers, gastritis, and stomach cancer: Pathology review
Inflammatory bowel disease: Pathology review
Malabsorption syndromes: Pathology review
Diverticular disease: Pathology review
Appendicitis: Pathology review
Gastrointestinal bleeding: Pathology review
Colorectal polyps and cancer: Pathology review
Pancreatitis: Pathology review
Gallbladder disorders: Pathology review
Jaundice: Pathology review
Viral hepatitis: Pathology review
Cirrhosis: Pathology review
Iron deficiency anemia
Sideroblastic anemia
Anemia of chronic disease
Lead poisoning
Hemolytic disease of the newborn
Autoimmune hemolytic anemia
Pyruvate kinase deficiency
Paroxysmal nocturnal hemoglobinuria
Aplastic anemia
Megaloblastic anemia
Folate (Vitamin B9) deficiency
Vitamin B12 deficiency
Diamond-Blackfan anemia
Vitamin K deficiency
Thrombotic thrombocytopenic purpura
Von Willebrand disease
Disseminated intravascular coagulation
Heparin-induced thrombocytopenia
Antithrombin III deficiency
Factor V Leiden
Protein C deficiency
Protein S deficiency
Antiphospholipid syndrome
Langerhans cell histiocytosis
Multiple myeloma
Microcytic anemia: Pathology review
Non-hemolytic normocytic anemia: Pathology review
Intrinsic hemolytic normocytic anemia: Pathology review
Extrinsic hemolytic normocytic anemia: Pathology review
Macrocytic anemia: Pathology review
Heme synthesis disorders: Pathology review
Coagulation disorders: Pathology review
Platelet disorders: Pathology review
Mixed platelet and coagulation disorders: Pathology review
Thrombosis syndromes (hypercoagulability): Pathology review
Lymphomas: Pathology review
Leukemias: Pathology review
Plasma cell disorders: Pathology review
Myeloproliferative disorders: Pathology review
Sepsis
Neonatal sepsis
Abscesses
Type I hypersensitivity
Food allergy
Anaphylaxis
Asthma
Type II hypersensitivity
Immune thrombocytopenia
Graves disease
Pemphigus vulgaris
Type III hypersensitivity
Serum sickness
Systemic lupus erythematosus
Poststreptococcal glomerulonephritis
Type IV hypersensitivity
Graft-versus-host disease
Contact dermatitis
Ruptured spleen
Immunodeficiencies: T-cell and B-cell disorders: Pathology review
Immunodeficiencies: Combined T-cell and B-cell disorders: Pathology review
Immunodeficiencies: Phagocyte and complement dysfunction: Pathology review
Folliculitis
Atopic dermatitis
Lichen planus
Pityriasis rosea
Psoriasis
Seborrhoeic dermatitis
Urticaria
Epidermolysis bullosa
Bullous pemphigoid
Stevens-Johnson syndrome
Cellulitis
Necrotizing fasciitis
Rotator cuff tear
Dislocated shoulder
Radial head subluxation (Nursemaid elbow)
Winged scapula
Thoracic outlet syndrome
Carpal tunnel syndrome
Ulnar claw
Erb-Duchenne palsy
Klumpke paralysis
Iliotibial band syndrome
Unhappy triad
Anterior cruciate ligament injury
Patellar tendon rupture
Meniscus tear
Patellofemoral pain syndrome
Sprained ankle
Achilles tendon rupture
Spondylolysis
Spondylolisthesis
Degenerative disc disease
Spinal disc herniation
Sciatica
Compartment syndrome
Rhabdomyolysis
Cleidocranial dysplasia
Osteoporosis
Osteopetrosis
Osteosclerosis
Lordosis, kyphosis, and scoliosis
Osteoarthritis
Rheumatoid arthritis
Fibromyalgia
Myasthenia gravis
Sjogren syndrome
Mixed connective tissue disease
Raynaud phenomenon
Scleroderma
Back pain: Pathology review
Rheumatoid arthritis and osteoarthritis: Pathology review
Seronegative and septic arthritis: Pathology review
Gout and pseudogout: Pathology review
Systemic lupus erythematosus (SLE): Pathology review
Scleroderma: Pathology review
Sjogren syndrome: Pathology review
Bone disorders: Pathology review
Bone tumors: Pathology review
Myalgias and myositis: Pathology review
Neuromuscular junction disorders: Pathology review
Cerebral palsy
Transient ischemic attack
Ischemic stroke
Epilepsy
Trigeminal neuralgia
Meningitis
Charcot-Marie-Tooth disease
Congenital neurological disorders: Pathology review
Headaches: Pathology review
Seizures: Pathology review
Cerebral vascular disease: Pathology review
Traumatic brain injury: Pathology review
Spinal cord disorders: Pathology review
Dementia: Pathology review
Central nervous system infections: Pathology review
Movement disorders: Pathology review
Demyelinating disorders: Pathology review
Adult brain tumors: Pathology review
Pediatric brain tumors: Pathology review
Neurocutaneous disorders: Pathology review
Renal agenesis
Horseshoe kidney
Potter sequence
Hyperphosphatemia
Hypophosphatemia
Hypernatremia
Hyponatremia
Hypermagnesemia
Hypomagnesemia
Hyperkalemia
Hypokalemia
Renal tubular acidosis
Minimal change disease
Focal segmental glomerulosclerosis (NORD)
Membranous nephropathy
Lupus nephritis
Membranoproliferative glomerulonephritis
Rapidly progressive glomerulonephritis
IgA nephropathy (NORD)
Hydronephrosis
Acute pyelonephritis
Chronic pyelonephritis
Prerenal azotemia
Renal azotemia
Acute tubular necrosis
Postrenal azotemia
Renal papillary necrosis
Renal cortical necrosis
Chronic kidney disease
Multicystic dysplastic kidney
Medullary cystic kidney disease
Medullary sponge kidney
Renal cell carcinoma
Angiomyolipoma
Nephroblastoma (Wilms tumor)
WAGR syndrome
Kidney stones
Lower urinary tract infection
Congenital renal disorders: Pathology review
Renal tubular defects: Pathology review
Renal tubular acidosis: Pathology review
Acid-base disturbances: Pathology review
Electrolyte disturbances: Pathology review
Renal failure: Pathology review
Nephrotic syndromes: Pathology review
Nephritic syndromes: Pathology review
Urinary incontinence: Pathology review
Urinary tract infections: Pathology review
Kidney stones: Pathology review
Renal and urinary tract masses: Pathology review
Ovarian cyst
Endometriosis
Fetal alcohol syndrome
Ovarian cysts and tumors: Pathology review
HIV and AIDS: Pathology review
Upper respiratory tract infection
Methemoglobinemia
Pneumonia
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Deep vein thrombosis and pulmonary embolism: Pathology review
Obstructive lung diseases: Pathology review
Apnea, hypoventilation and pulmonary hypertension: Pathology review
Baroreceptors
Chemoreceptors
Renin-angiotensin-aldosterone system
Adrenocorticotropic hormone
Growth hormone and somatostatin
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Antidiuretic hormone
Thyroid hormones
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Phosphate, calcium and magnesium homeostasis
Parathyroid hormone
Vitamin D
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Anatomy and physiology of the teeth
Chewing and swallowing
Carbohydrates and sugars
Fats and lipids
Proteins
Vitamins and minerals
Intestinal fluid balance
Pancreatic secretion
Bile secretion and enterohepatic circulation
Prebiotics and probiotics
Platelet plug formation (primary hemostasis)
Coagulation (secondary hemostasis)
Role of Vitamin K in coagulation
Clot retraction and fibrinolysis
Innate immune system
Complement system
T-cell development
B-cell development
MHC class I and MHC class II molecules
T-cell activation
B-cell activation and differentiation
Cell-mediated immunity of CD4 cells
Cell-mediated immunity of natural killer and CD8 cells
Antibody classes
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VDJ rearrangement
Contracting the immune response and peripheral tolerance
B- and T-cell memory
Anergy, exhaustion, and clonal deletion
Vaccinations
Ascending and descending spinal tracts
Sympathetic nervous system
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Enteric nervous system
Basal ganglia: Direct and indirect pathway of movement
Memory
Learning
Stress
Emotion
Renal system anatomy and physiology
Glomerular filtration
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Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Erythropoietin
Respiratory acidosis
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Metabolic alkalosis
Menstrual cycle
Anticoagulants: Direct factor inhibitors
Assessments
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High Yield Notes
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Unhappy triad
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A 33-year-old man presents to the emergency department following a right knee injury. The patient was playing rugby when an opposing teammate tackled him. He felt a “pop” in the right knee and experienced pain after that. The patient is otherwise healthy. Physical examination demonstrates a large right knee effusion, a positive anterior drawer test, and a positive valgus stress test. Vital signs are within normal limits. An MRI of the patient's right knee is shown below. Which of the following is the most likely mechanism of injury that resulted in this patient’s condition?
Image reproduced from Radiopedia
Image reproduced from Radiopedia
External References
First Aid
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2022
2021
Anterior cruciate ligament (ACL) injury
“unhappy triad,” p. 459
Medial collateral ligament (MCL) injury
in “unhappy triad,” p. 459
“Unhappy triad”(knee injuries) p. 459
Summary
An unhappy triad, also known as O'Donoghue's triad, is a common injury that occurs in the knee joint. It involves damage to the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus. The injury usually occurs as a result of a sudden forceful twist or impact on the knee joint, such as during a sports activity. The lateral meniscus may also be involved in some cases. This injury is typically treated with surgery and physical therapy.