Overview Snapshot A 21-year-old man presents to the emergency department for severe pain in the right knee. A few hours prior to presentation, an opposing football player hits his leg from his right side. Afterwards, he felt a "pop" sound that was followed by severe knee pain and a sensation of knee instability. On physical exam, there is anterior translation of the proximal tibia when pulled as the patient has the knee flexed at 90° and supine. Ice is applied to the knee and ibuprofen is prescribed. Orthopedic surgery is consulted to evaluate if ligamental reconstruction is needed. Introduction Clinical definition injury in the form of tear or rupture affecting the anterior cruciate ligament (ACL) in the knee Epidemiology incidence non-contact ACL injuries are more common demographics more common in female athletes risk factors sports (e.g., football, soccer, skiers, and basketball) motor vehicle accidents Pathoanatomy normal anatomy the ACL course originates in the posteromedial aspect of the lateral femoral condyle reaches the anteromedial aspect of the tibia the ACL plays an important role in knee stability it controls anterior translation of the tibia it also restrains against tibial rotation, varus, and valgus stress pathology contact mechanisms injury that causes hyperextension or valgus deformation of the knee e.g., football injury high-speed motor vehicle accident non-contact mechanisms changing direction, pivoting, or landing that leads to rotation or valgus stress of the knee after sudden deceleration Associated conditions unhappy triad which consists of injury to the ACL medial collateral ligament medial meniscus Prognosis the majority of athletes are able to return to their sports activities with ACL reconstruction Presentation Symptoms feeling a "pop" in the knee thereafter, there is acute swelling and pain instability or "giving out" knee Physical exam anterior drawer test the proximal tibia is anteriorly pulled while the patient is supine and the knee is flexed at 90 degrees if there is anterior translation then the test is positive Lachman test the proximal tibia is anteriorly pulled with one hand, while the other hand stabilizes the distal femur while the knee is flexed at 30 degrees hemarthrosis Imaging Magnetic resonance imaging (MRI) indication an imaging modality that can confirm the diagnosis if reconstruction is a possibility or to identify concomitant knee pathology Studies Making the diagnosis can be made based on typical clinical presentation alone can be confirmed by MRI or knee arthroscopy Differential Meniscal tear differentiating factor patients can have a positive Thessaly test McMurray test Apley test Posterior collateral ligament (PCL) injury differentiating factor patients can have a positive posterior drawer test Treatment Conservative rest, ice, compression, and elevation (RICE) therapy indication management to reduce pain, edema, and hemarthrosis in the acute stage of the injury nonsteroidal anti-inflammatory drugs are typically added Operative surgical reconstruction indications performed in young and active patients with high demand sports or jobs significant knee instability such as injuries affecting multiple knee structures (e.g., unhappy triad) Complications Osteoarthritis Arthrosis Sports disability
QUESTIONS 1 of 1 1 Previous Next Lab Values Blood Hematologic Cerebrospinal Sweat, Urine, and BMI Blood, Plasma, Serum Reference Range ALT 8-20 U/L Amylase, serum 25-125 U/L AST 8-20 U/L Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL Calcium, serum (Ca2+) 8.4-10.2 mg/dL Cholesterol, serum Rec: < 200 mg/dL Cortisol, serum 0800 h: 5-23 μg/dL //1600 h: 3-15 μg/dL 2000 h: ≤ 50% of 0800 h Creatine kinase, serum Male: 25-90 U/LFemale: 10-70 U/L Creatinine, serum 0.6-1.2 mg/dL Electrolytes, serum Sodium (Na+) 136-145 mEq/L Chloride (Cl-) 95-105 mEq/L Potassium (K+) 3.5-5.0 mEq/L Bicarbonate (HCO3-) 22-28 mEq/L Magnesium (Mg2+) 1.5-2.0 mEq/L Estriol, total, serum (in pregnancy) 24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL 28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL Ferritin, serum Male: 15-200 ng/mLFemale: 12-150 ng/mL Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL Female: premenopause: 4-30 mIU/mL midcycle peak: 10-90 mIU/mL postmenopause: 40-250 pH 7.35-7.45 PCO2 33-45 mmHg PO2 75-105 mmHg Glucose, serum Fasting: 70-110 mg/dL2-h postprandial:<120 mg/dL Growth hormone - arginine stimulation Fasting: <5 ng/mLProvocative stimuli: > 7ng/mL Immunoglobulins, serum IgA 76-390 mg/dL IgE 0-380 IU/mL IgG 650-1500 mg/dL IgM 40-345 mg/dL Iron 50-170 μg/dL Lactate dehydrogenase, serum 45-90 U/L Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL Female: follicular phase: 5-30 mIU/mL midcycle: 75-150 mIU/mL postmenopause 30-200 mIU/mL Osmolality, serum 275-295 mOsmol/kd H2O Parathyroid hormone, serume, N-terminal 230-630 pg/mL Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L Phosphorus (inorganic), serum 3.0-4.5 mg/dL Prolactin, serum (hPRL) < 20 ng/mL Proteins, serum Total (recumbent) 6.0-7.8 g/dL Albumin 3.5-5.5 g/dL Globulin 2.3-3.5 g/dL Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h Thyroxine (T4), serum 5-12 μg/dL Triglycerides, serum 35-160 mg/dL Triiodothyronine (T3), serum (RIA) 115-190 ng/dL Triiodothyronine (T3) resin uptake 25%-35% Urea nitrogen, serum 7-18 mg/dL Uric acid, serum 3.0-8.2 mg/dL Hematologic Reference Range Bleeding time 2-7 minutes Erythrocyte count Male: 4.3-5.9 million/mm3Female: 3.5-5.5 million mm3 Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/hFemale: 0-20 mm/h Hematocrit Male: 41%-53%Female: 36%-46% Hemoglobin A1c ≤ 6 % Hemoglobin, blood Male: 13.5-17.5 g/dLFemale: 12.0-16.0 g/dL Hemoglobin, plasma 1-4 mg/dL Leukocyte count and differential Leukocyte count 4,500-11,000/mm3 Segmented neutrophils 54%-62% Bands 3%-5% Eosinophils 1%-3% Basophils 0%-0.75% Lymphocytes 25%-33% Monocytes 3%-7% Mean corpuscular hemoglobin 25.4-34.6 pg/cell Mean corpuscular hemoglobin concentration 31%-36% Hb/cell Mean corpuscular volume 80-100 μm3 Partial thromboplastin time (activated) 25-40 seconds Platelet count 150,000-400,000/mm3 Prothrombin time 11-15 seconds Reticulocyte count 0.5%-1.5% of red cells Thrombin time < 2 seconds deviation from control Volume Plasma Male: 25-43 mL/kgFemale: 28-45 mL/kg Red cell Male: 20-36 mL/kgFemale: 19-31 mL/kg Cerebrospinal Fluid Reference Range Cell count 0-5/mm3 Chloride 118-132 mEq/L Gamma globulin 3%-12% total proteins Glucose 40-70 mg/dL Pressure 70-180 mm H2O Proteins, total < 40 mg/dL Sweat Reference Range Chloride 0-35 mmol/L Urine Calcium 100-300 mg/24 h Chloride Varies with intake Creatinine clearance Male: 97-137 mL/minFemale: 88-128 mL/min Estriol, total (in pregnancy) 30 wks 6-18 mg/24 h 35 wks 9-28 mg/24 h 40 wks 13-42 mg/24 h 17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 hFemale: 2.0-8.0 mg/24 h 17-Ketosteroids, total Male: 8-20 mg/24 hFemale: 6-15 mg/24 h Osmolality 50-1400 mOsmol/kg H2O Oxalate 8-40 μg/mL Potassium Varies with diet Proteins, total < 150 mg/24 h Sodium Varies with diet Uric acid Varies with diet Body Mass Index (BMI) Adult: 19-25 kg/m2 Calculator ( ) xy AC 7 8 9 ÷ 4 5 6 × 1 2 3 - 0 . = + (M2.OR.17.4799) A 25-year-old male presents to his primary care physician for pain in his knee. The patient was in a wrestling match when his legs were grabbed from behind and he was taken to the floor. The patient states that the moment this impact happened, he felt a snapping and sudden pain in his knee. When the match ended and he stood back up, his knee felt unstable. Minutes later, his knee was swollen and painful. Since then, the patient claims that he has felt unstable bearing weight on the leg. The patient has no significant past medical history, and is currently taking a multivitamin and protein supplements. On physical exam you note a tender right knee, with erythema and an effusion. Which of the following is the most likely physical exam finding in this patient? Review Topic | Tested Concept QID: 109202 Type & Select Correct Answer 1 Laxity to valgus stress 0% (0/2) 2 Laxity to varus stress 0% (0/2) 3 Clicking and locking of the joint with motion 0% (0/2) 4 Anterior translation of the tibia relative to the femur 50% (1/2) 5 Posterior translation of the tibia relative to the femur 50% (1/2) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review tested concept
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