Joint replacement basics (hip US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Joint replacement basics (hip. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Joint replacement basics (hip US Medical PG Question 1: A 69-year-old man presents to his primary care physician for pain when he walks. He states that the pain is the worst in his left great toe but is also present in his hips and knees. He says that his symptoms are worse with activity and tend to improve with rest. His symptoms have progressively worsened over the past several years. He has a past medical history of obesity, type II diabetes mellitus, smoking, and hypertension. He drinks roughly ten beers per day. His current medications include metformin, insulin, lisinopril, and hydrochlorothiazide. The patient has a recent travel history to Bangkok where he admits to having unprotected sex. On physical exam, examination of the lower extremity results in pain. There is crepitus of the patient's hip when his thigh is flexed and extended. Which of the following is the most likely diagnosis?
- A. Pseudogout
- B. Gout
- C. Rheumatoid arthritis
- D. Infectious arthritis
- E. Osteoarthritis (Correct Answer)
Joint replacement basics (hip Explanation: ***Osteoarthritis***
- The patient presents with classic features of **osteoarthritis (OA)**: **progressive worsening over several years**, pain that is **worse with activity and improves with rest** (mechanical pain pattern), and **crepitus of the hip** on examination.
- **Crepitus** is a hallmark physical finding in OA, indicating cartilage degradation and bone-on-bone contact.
- The patient has major risk factors including **age (69 years)**, **obesity**, and involvement of **weight-bearing joints** (hips and knees).
- While the great toe is also affected, polyarticular OA commonly involves multiple joints including the first metatarsophalangeal joint.
*Gout*
- Although the patient has risk factors for gout (**alcohol consumption** and **thiazide diuretic use**), gout typically presents with **acute, severe attacks** of monoarticular arthritis, not chronic progressive pain over several years.
- Acute gout would present with sudden onset of severe pain, erythema, warmth, and swelling, which are not described in this case.
- The **mechanical pain pattern** (worse with activity, better with rest) and **crepitus** are inconsistent with gout.
*Pseudogout*
- Pseudogout (calcium pyrophosphate deposition disease) typically causes **acute attacks** affecting larger joints like the knees, similar to gout.
- The **chronic progressive nature** of this patient's symptoms over several years, along with crepitus, is not consistent with pseudogout.
- Pseudogout does not explain the mechanical pain pattern or the hip crepitus.
*Infectious arthritis*
- While the patient's recent travel and unprotected sex raise concern for sexually transmitted infections, **septic arthritis** would present with **acute onset**, severe pain, fever, warmth, erythema, and systemic signs of infection.
- The **chronic progressive course over several years** is completely inconsistent with infectious arthritis.
- Gonococcal arthritis can cause migratory polyarthritis but would be acute, not chronic.
*Rheumatoid arthritis*
- Rheumatoid arthritis typically presents with **symmetric polyarthritis** affecting small joints of the hands and feet, with **prolonged morning stiffness** (>30-60 minutes).
- The pain pattern in RA is **inflammatory** (worse with rest, improves with activity), which is the **opposite** of this patient's presentation.
- **Crepitus** and mechanical pain pattern point to a degenerative process (OA), not an inflammatory arthropathy like RA.
Joint replacement basics (hip US Medical PG Question 2: A 6-week-old boy is brought for routine examination at his pediatrician’s office. The patient was born at 39 weeks to a 26-year-old G1P1 mother by normal vaginal delivery. External cephalic version was performed successfully at 37 weeks for breech presentation. Pregnancy was complicated by gestational diabetes that was well-controlled with insulin. The patient’s maternal grandmother has early onset osteoporosis. On physical examination, the left hip dislocates posteriorly with adduction and depression of a flexed femur. An ultrasound is obtained that reveals left acetabular dysplasia and a dislocated left femur. Which of the following is the next best step in management?
- A. Pavlik harness (Correct Answer)
- B. Closed reduction and spica casting
- C. Observation
- D. Physiotherapy
- E. Open reduction and femoral osteotomy
Joint replacement basics (hip Explanation: ***Pavlik harness***
- A Pavlik harness is the **gold standard treatment** for **developmental dysplasia of the hip (DDH)** in infants younger than 6 months. It maintains the hips in a **flexed and abducted position**, promoting proper acetabular development and hip reduction.
- The patient's age (6 weeks), clear diagnosis of **acetabular dysplasia**, and a dislocated hip on ultrasound make the Pavlik harness the **most appropriate and least invasive initial treatment**.
*Closed reduction and spica casting*
- This treatment is typically reserved for children older than 6 months or those who **fail Pavlik harness treatment**.
- It involves a more aggressive reduction technique, often requiring **anesthesia**, and is followed by prolonged immobilization in a **spica cast**.
*Observation*
- **Observation is not appropriate** for a 6-week-old infant with a **diagnosed dislocated hip** and **acetabular dysplasia**.
- Untreated DDH can lead to **permanent hip instability**, pain, and early arthritis.
*Physiotherapy*
- While physiotherapy may play a role in rehabilitation after other interventions, it is **not sufficient as a primary treatment** for a dislocated hip in an infant.
- It cannot achieve or maintain the necessary **reduction and stabilization** required for proper hip development.
*Open reduction and femoral osteotomy*
- This is an **invasive surgical procedure** typically reserved for older children (older than 18-24 months) or in cases of **failed non-operative management** and closed reduction, especially in irreducible or severely dysplastic hips.
- It involves directly opening the joint to reduce the hip and may include reshaping bone (osteotomy) to improve hip stability. This is **premature** for a 6-week-old.
Joint replacement basics (hip US Medical PG Question 3: Following a motor vehicle accident, a 63-year-old man is scheduled for surgery. The emergency physician notes a posture abnormality in the distal left lower limb and a fracture-dislocation of the right hip and acetabulum based on the radiology report. The senior orthopedic resident mistakenly notes a fracture dislocation of the left hip. The surgeon's examination of the patient in the operating room shows an externally rotated and shortened left lower limb. The surgeon reduces the left hip and inserts a pin in the left tibia. A review of postoperative imaging leads to a second surgery on the fracture-dislocation of the right hip. Which of the following strategies is most likely to prevent the recurrence of this type of error?
- A. Marking the surgical site
- B. Implementing a checklist
- C. Conducting a preoperative time-out (Correct Answer)
- D. Verifying the patient’s identity
- E. Performing screening X-rays
Joint replacement basics (hip Explanation: ***Conducting a preoperative time-out***
- A **preoperative time-out** is a crucial step in the Universal Protocol, ensuring that the entire surgical team confirms the correct patient, correct site, and correct procedure immediately before incision. This would have caught the discrepancy between the planned surgery and the surgeon's actions.
- The surgical time-out provides a final opportunity for all team members to voice concerns or identify errors, preventing wrong-site surgery as occurred here.
*Marking the surgical site*
- While **surgical site marking** is part of the Universal Protocol, it primarily prevents wrong-side or wrong-level surgery when multiple potential sites exist or when laterality is critical.
- In this scenario, the issue was a misidentification of the *injured* hip at the point of action, not necessarily an ambiguity on which limb *to mark*. The surgeon operated on the palpably injured hip, but it was the wrong one according to the actual diagnosis.
*Implementing a checklist*
- Implementing a comprehensive **surgical safety checklist** can reduce errors across many domains, but its effectiveness depends on strict adherence and a culture of safety.
- While valuable, a checklist alone might not have prevented this specific error if the initial misinterpretation of the radiology report by the resident wasn't explicitly cross-checked at a critical "stop" point.
*Verifying the patient’s identity*
- **Verifying patient identity** is a fundamental safety measure at multiple points, including admission, consent, and before surgery, but it prevents operating on the wrong patient.
- In this case, the correct patient was identified; the error was related to the specific surgical site on that patient.
*Performing screening X-rays*
- **Screening X-rays** are typically performed to assess the extent of injury and confirm the diagnosis before surgery. This was done, and the radiology report correctly identified the right hip injury.
- The error arose from the *interpretation* and *communication* of these findings, not the absence of imaging itself. The existing radiology report, if properly reviewed and confirmed, would have prevented the error.
Joint replacement basics (hip US Medical PG Question 4: A 65-year-old man comes to a follow-up appointment with his surgeon 2 months after undergoing hip replacement surgery. His major concern at this visit is that he is still limping since the surgery even after the post-operative pain has subsided. Specifically, when he stands on his right leg, he feels that he has to lean further to the right in order to maintain balance. When standing on his left leg, he feels that he is able to step normally. Damage to which of the following nerves would most likely present with this patient's symptoms?
- A. Common peroneal nerve
- B. Tibial nerve
- C. Femoral nerve
- D. Inferior gluteal nerve
- E. Superior gluteal nerve (Correct Answer)
Joint replacement basics (hip Explanation: ***Superior gluteal nerve***
- The superior gluteal nerve innervates the **gluteus medius** and minimus muscles, which are crucial for **hip abduction** and stabilizing the pelvis during gait.
- Damage to this nerve or its muscles on one side (e.g., right side) would lead to a **Trendelenburg gait**, where the pelvis drops on the unaffected side when standing on the affected leg, and the patient compensates by leaning towards the affected side.
*Common peroneal nerve*
- The common peroneal nerve primarily innervates muscles responsible for **dorsiflexion** and **eversion of the foot**.
- Damage to this nerve commonly results in **foot drop** and an inability to evert the foot, which is not the primary symptom described.
*Tibial nerve*
- The tibial nerve innervates muscles responsible for **plantarflexion** and **inversion of the foot**, as well as the intrinsic muscles of the sole.
- Injury typically presents with difficulty walking on tiptoes, toe curling, and sensory loss in the sole of the foot, not pelvic instability.
*Femoral nerve*
- The femoral nerve innervates the **quadriceps femoris** and sartorius muscles,
- Damage leads to weakness in **knee extension** and loss of sensation over the anterior thigh and medial leg.
*Inferior gluteal nerve*
- The inferior gluteal nerve innervates the **gluteus maximus** muscle, which is essential for **hip extension** and external rotation.
- Damage would primarily affect activities like climbing stairs or standing up from a seated position, rather than the specific lateral pelvic instability described.
Joint replacement basics (hip US Medical PG Question 5: Three hours after undergoing left hip arthroplasty for chronic hip pain, a 62-year-old man complains of a prickling sensation in his left anteromedial thigh and lower leg. He has never had these symptoms before. He has hyperlipidemia and coronary artery disease. He has had recent right-sided gluteal and thigh pain with ambulation. Vital signs are within normal limits. Sensation to pinprick and light touch are decreased on the anteromedial left thigh as well as medial lower leg. Neurologic exam shows left leg strength 3/5 on hip flexion and 2/5 on knee extension. Patellar reflex is decreased on the left. The remainder of neurologic exam is normal. Dorsalis pedis, popliteal, and femoral pulses are 2+ bilaterally. The surgical incision is without erythema or drainage. Which of the following is the most likely underlying cause of this patient's symptoms?
- A. Surgical site infection
- B. Obturator nerve injury
- C. Sural nerve injury
- D. Femoral nerve injury (Correct Answer)
- E. Femoral artery occlusion
Joint replacement basics (hip Explanation: ***Femoral nerve injury***
- The patient's symptoms of **prickling sensation (paresthesia)** in the anterior-medial thigh and medial lower leg, **decreased sensation to pinprick and light touch** in these areas, and **weakness in hip flexion (iliopsoas)** and **knee extension (quadriceps)**, along with a **decreased patellar reflex**, are all classic signs of **femoral nerve dysfunction**.
- The femoral nerve can be susceptible to injury during **hip arthroplasty** due to retraction, direct trauma, or hematoma formation, especially if the patient is slim or has anatomical variations.
*Surgical site infection*
- This typically presents with signs of **inflammation** such as erythema, warmth, severe pain, and sometimes drainage from the incision site, which are absent here.
- Neurological deficits like specific motor weakness and sensory loss in a nerve distribution are *not* primary features of a surgical site infection.
*Obturator nerve injury*
- An obturator nerve injury would primarily affect **adduction of the thigh** and might cause sensory changes in the medial thigh, but would *not* cause weakness in hip flexion or knee extension, nor would it affect the patellar reflex.
- The sensory distribution described (anteromedial thigh and medial lower leg) is more consistent with femoral nerve involvement than obturator nerve.
*Sural nerve injury*
- **Sural nerve injury** primarily causes sensory deficits along the **posterolateral aspect of the lower leg and ankle**, and the lateral aspect of the foot.
- It would *not* cause motor weakness in hip flexion or knee extension, nor would it affect the patellar reflex.
*Femoral artery occlusion*
- **Femoral artery occlusion** would cause symptoms of **acute limb ischemia**, including severe pain, pallor, pulselessness, poikilothermia (coldness), paresthesias, and paralysis (the "6 Ps").
- While paresthesias are present, the patient has **intact distal pulses (2+ bilaterally)** and no signs of pallor or coldness, ruling out significant arterial occlusion.
Joint replacement basics (hip US Medical PG Question 6: A 25-year-old woman is brought to the emergency department after being involved in a rear-end collision, in which she was the restrained driver of the back car. On arrival, she is alert and active. She reports pain in both knees and severe pain over the right groin. Temperature is 37°C (98.6°F), pulse is 116/min, respirations are 19/min, and blood pressure is 132/79 mm Hg. Physical examination shows tenderness over both knee caps. The right groin is tender to palpation. The right leg is slightly shortened, flexed, adducted, and internally rotated. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?
- A. Anterior hip dislocation
- B. Posterior hip dislocation (Correct Answer)
- C. Femoral neck fracture
- D. Pelvic fracture
- E. Femoral shaft fracture
Joint replacement basics (hip Explanation: ***Posterior hip dislocation***
- The classic presentation of **posterior hip dislocation** involves the affected leg being **shortened, flexed, adducted, and internally rotated**, as described in the patient.
- This type of injury commonly occurs in **motor vehicle collisions** where the knee strikes the dashboard (dashboard injury), transmitting force up the femur to the hip joint, often causing the femoral head to dislocate posteriorly.
*Anterior hip dislocation*
- This typically presents with the affected leg in a position of **hip flexion, abduction, and external rotation**, which is contrary to the findings in this patient.
- Anterior dislocations are less common than posterior dislocations and usually result from a traumatic force applied to the hip while it is in **abduction and external rotation**.
*Femoral neck fracture*
- While a **femoral neck fracture** can cause pain and shortening of the leg, the typical presentation is usually one of **external rotation**, not internal rotation.
- The distinct **flexion, adduction, and internal rotation** triad is highly suggestive of hip dislocation, not a fracture of the femoral neck.
*Pelvic fracture*
- A **pelvic fracture** would likely present with more diffuse pelvic pain, potentially instability upon palpation of the pelvis, and possibly lower extremity neurological deficits or genitourinary symptoms depending on the fracture type.
- The specific limb positioning observed (shortened, flexed, adducted, internally rotated) is not a hallmark of an isolated pelvic fracture.
*Femoral shaft fracture*
- A **femoral shaft fracture** would cause severe pain along the shaft of the femur, significant swelling, and obvious deformity of the thigh.
- While the leg might be shortened, the specific combination of **flexion, adduction, and internal rotation** primarily points towards a hip joint issue rather than a mid-shaft fracture.
Joint replacement basics (hip US Medical PG Question 7: A 63-year-old female recovering from a total shoulder arthroplasty completed 6 days ago presents complaining of joint pain in her repaired shoulder. Temperature is 39 degrees Celsius. Physical examination demonstrates erythema and significant tenderness around the incision site. Wound cultures reveal Gram-positive cocci that are resistant to nafcillin. Which of the following organisms is the most likely cause of this patient's condition?
- A. Streptococcus pyogenes
- B. Escherichia coli
- C. Streptococcus viridans
- D. Staphylococcus epidermidis
- E. Staphylococcus aureus (Correct Answer)
Joint replacement basics (hip Explanation: ***Staphylococcus aureus***
- The combination of **post-surgical infection**, **erythema**, and fever with **Gram-positive cocci** that are **nafcillin-resistant** is highly indicative of **Methicillin-Resistant Staphylococcus aureus (MRSA)**.
- *S. aureus* is a common cause of **surgical site infections**, and its resistance to nafcillin implies it is MRSA, a significant clinical concern for its difficulty in treatment.
*Streptococcus pyogenes*
- While *S. pyogenes* is a Gram-positive coccus that can cause skin and soft tissue infections, it is typically **susceptible to penicillin** and related antibiotics like nafcillin, unlike the organism described.
- It is more commonly associated with **streptococcal pharyngitis** or **cellulitis**, and while it can cause severe disease, its resistance profile doesn't match the clinical picture.
*Escherichia coli*
- *E. coli* is a **Gram-negative rod**, not a Gram-positive coccus.
- It is a common cause of **urinary tract infections** and **gastrointestinal infections**, making it an unlikely pathogen for a post-surgical joint infection unless contaminated from a visceral source.
*Streptococcus viridans*
- **Viridans streptococci** are Gram-positive cocci but are typically associated with **endocarditis** or dental infections, especially after poor dental hygiene or procedures.
- They are usually **susceptible to penicillin** and do not typically exhibit nafcillin resistance as the primary feature in a post-arthroplasty infection.
*Staphylococcus epidermidis*
- *S. epidermidis* is a **coagulase-negative Staphylococcus** known for forming **biofilms on prosthetic devices**, leading to chronic, low-grade infections.
- While it can be nafcillin-resistant, the **acute presentation** with fever and significant inflammation suggests a more virulent pathogen like *S. aureus*, as *S. epidermidis* infections are typically indolent.
Joint replacement basics (hip US Medical PG Question 8: A 6-year-old boy presents to his primary care physician with hip pain that started this morning. The patient claims the pain is severe and is stopping him from skateboarding. The patient recently recovered from an upper respiratory infection that he caught from his siblings but has otherwise been healthy. The patient has a past medical history of obesity. His temperature is 98.1°F (36.7°C), blood pressure is 100/55 mmHg, pulse is 90/min, respirations are 22/min, and oxygen saturation is 98% on room air. On physical exam, you note an obese boy in no acute distress. Cardiopulmonary exam is within normal limits. Inspection of the hip reveals no abnormalities or swelling. The hip exhibits a normal range of motion and physical exam only elicits minor pain. The patient's gait appears normal and pain is elicited when the patient jumps or runs. Which of the following is the best next step in management for this patient's most likely diagnosis?
- A. Ibuprofen and rest (Correct Answer)
- B. Radiography
- C. CT scan
- D. MRI
- E. Aspiration and broad spectrum antibiotics
Joint replacement basics (hip Explanation: ***Ibuprofen and rest***
- This patient's presentation with hip pain after an **upper respiratory infection**, normal physical exam findings except for pain on high-impact activities, and absence of fever, points towards **transient synovitis of the hip**.
- **Treatment for transient synovitis** is supportive, involving anti-inflammatory medications like ibuprofen and rest, as it is a self-limiting condition.
*Radiography*
- While imaging might be considered, **radiographs of the hip** are typically normal in transient synovitis and are primarily used to rule out other more serious conditions like Legg-Calvé-Perthes disease or slipped capital femoral epiphysis, which usually present with more distinct physical exam findings or chronic symptoms.
- Given the acute onset, recent viral illness, and mild exam findings, this is not the immediate next step for the most likely diagnosis.
*CT scan*
- A **CT scan** exposes the patient to radiation and is generally not indicated as a first-line diagnostic tool for transient synovitis due to its low diagnostic yield for this condition and higher cost compared to other modalities.
- It would only be considered if there was a strong suspicion of bony pathology not visible on plain radiographs or if surgery was being contemplated.
*MRI*
- An **MRI** would be highly sensitive for detecting inflammation or effusion in the hip joint, but it is an expensive and time-consuming procedure typically reserved for cases where the diagnosis is unclear or other serious conditions are strongly suspected (e.g., osteomyelitis, avascular necrosis).
- It is not necessary for the initial management of suspected transient synovitis, which is a clinical diagnosis.
*Aspiration and broad spectrum antibiotics*
- **Aspiration of the joint** and treatment with broad-spectrum antibiotics are indicated for **septic arthritis**, which is characterized by fever, significant pain with even gentle passive range of motion, and elevated inflammatory markers.
- This patient is afebrile, has only minor pain on physical exam, and has no systemic signs of infection, making septic arthritis highly unlikely.
Joint replacement basics (hip US Medical PG Question 9: A previously healthy 33-year-old woman comes to the physician because of pain and sometimes numbness in her right thigh for the past 2 months. She reports that her symptoms are worse when walking or standing and are better while sitting. Three months ago, she started going to a fitness class a couple times a week. She is 163 cm (5 ft 4 in) tall and weighs 88 kg (194 lb); BMI is 33.1 kg/m2. Her vital signs are within normal limits. Examination of the skin shows no abnormalities. Sensation to light touch is decreased over the lateral aspect of the right anterior thigh. Muscle strength is normal. Tapping the right inguinal ligament leads to increased numbness of the affected thigh. The straight leg test is negative. Which of the following is the most appropriate next step in management of this patient?
- A. Advise patient to wear looser pants (Correct Answer)
- B. Reduction of physical activity
- C. MRI of the lumbar spine
- D. X-ray of the hip
- E. Blood work for inflammatory markers
Joint replacement basics (hip Explanation: ***Advise patient to wear looser pants***
- This patient presents with symptoms consistent with **meralgia paresthetica**, a condition caused by compression of the **lateral femoral cutaneous nerve (LFCN)**. Modifying clothing or belts that compress the inguinal ligament can relieve pressure on the nerve.
- Her increased weight, a recent increase in physical activity, and a positive Tinel's sign at the inguinal ligament (tapping leads to increased numbness) support this diagnosis.
*Reduction of physical activity*
- While excessive physical activity can contribute to meralgia paresthetica, simply reducing it without addressing the underlying compression might not fully resolve symptoms.
- The patient has recently increased physical activity, which could be a contributing factor, but it's not the primary or most direct intervention for nerve compression.
*MRI of the lumbar spine*
- An MRI of the lumbar spine would be considered if there were signs of **radiculopathy** or other spinal pathology, such as weakness, reflex changes, or a positive straight leg test, which are absent here.
- The symptoms are localized to the distribution of the LFCN, and the physical exam points away from a central spinal cause.
*X-ray of the hip*
- An X-ray of the hip would be indicated for suspected **hip joint pathology** or **bony abnormalities**, which are not suggested by the patient's symptoms (pain and numbness in the thigh, not hip joint pain).
- Meralgia paresthetica is a nerve entrapment syndrome, not a structural issue of the hip joint.
*Blood work for inflammatory markers*
- Inflammatory markers like **ESR** or **CRP** would be relevant if an **inflammatory arthritis**, infection, or systemic inflammatory condition was suspected, but the patient's symptoms are purely neurological and localized.
- There is no clinical evidence of inflammation, fever, or joint swelling to suggest an underlying inflammatory process.
Joint replacement basics (hip US Medical PG Question 10: A 25-year-old man comes to the physician because of left-sided knee pain for 2 weeks. The pain started while playing basketball after suddenly hearing a popping sound. He has been unable to run since this incident. He has asthma, allergic rhinitis, and had a progressive bilateral sensorineural hearing impairment at birth treated with cochlear implants. His only medication is a salbutamol inhaler. The patient appears healthy and well-nourished. His temperature is 37°C (98.6°F), pulse is 67/min, and blood pressure is 120/80 mm Hg. Examination of the left knee shows medial joint line tenderness. Total knee extension is not possible and a clicking sound is heard when the knee is extended. An x-ray of the left knee shows no abnormalities. Which of the following is the most appropriate next step in the management of this patient?
- A. Reassurance and follow-up
- B. Arthrocentesis of the left knee
- C. Open meniscal repair
- D. Arthroscopy of the left knee
- E. MRI scan of the left knee (Correct Answer)
Joint replacement basics (hip Explanation: ***MRI scan of the left knee***
- The patient's presentation with a **popping sound**, inability to run, **medial joint line tenderness**, limited extension, and a clicking sound suggests a **meniscal tear**, which is not visible on X-ray.
- An **MRI scan** is the *most appropriate* next step as it is the **gold standard** for diagnosing meniscal tears and other soft tissue injuries of the knee.
*Reassurance and follow-up*
- This option is *inappropriate* given the clear signs and symptoms of a **significant knee injury** that warrants further investigation.
- Delaying diagnosis and treatment could lead to **worsening of the injury** and chronic pain.
*Arthrocentesis of the left knee*
- Arthrocentesis involves aspirating joint fluid, which is primarily indicated for diagnosing **septic arthritis** or **gout**, neither of which is suggested by this patient's acute trauma history.
- While a meniscal tear can cause an effusion, the primary diagnostic goal here is imaging the soft tissue injury, not analyzing synovial fluid.
*Open meniscal repair*
- **Open meniscal repair** is a surgical intervention, and it is *premature* to consider surgery before a definitive diagnosis is established.
- The *most appropriate* initial step after physical exam and X-ray is often an MRI to confirm the pathology.
*Arthroscopy of the left knee*
- **Arthroscopy** is both a **diagnostic and therapeutic procedure**, but it is generally reserved after non-invasive imaging like MRI has been performed.
- Although it can confirm a meniscal tear, an MRI is less invasive and can provide comparable if not superior detail for surgical planning.
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