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Home , Lunate bone, Pubofemoral ligament, Unhappy triad

Lab 8— of Upper/Lower Limb Acromioclavicular – QuesƟons 1 of 1

1. An 18-year-old man injures the right from a down- ward blow on the point of the shoulder. The of the lies anteroinferior to the lateral end of the . There is tenderness in the region between the acromion and the lateral end of the clavicle and pain when abducting the right up to or above the level of the shoulder. Anteroposterior (AP) radiographs show that the acromioclavicular and coracoclavicu- lar spaces in the right shoulder are each more than 50% wider than the corresponding spaces in the left shoulder. The AP radi- ographs of the indicate which of the following liga- ments is significantly ruptured in the right shoulder? A. costoclavicular B. coracoacromial ligament C. coracohumeral ligament D. coracoclavicular ligament E. suprascapular ligament

2. An 18-year-old man injures the right shoulder from a down- ward blow on the point of the shoulder. The acromion of the scapula lies anteroinferior to the lateral end of the clavicle. There is tenderness in the region between the acromion and the lateral end of the clavicle and pain when abducting the right arm up to or above the level of the shoulder. Anteroposterior (AP) radiographs show that the acromioclavicular and coracoclavicu- lar spaces in the right shoulder are each more than 50% wider than the corresponding spaces in the left shoulder. Which bony structure lies DIRECTLY beneath the skin at the point of the shoulder? A. acromion of the scapula B. of the scapula C. spine of the scapula D. superior angle of the scapula E. head of the

3. An 18-year-old man injures the right shoulder from a down- ward blow on the point of the shoulder. The acromion of the scapula lies anteroinferior to the lateral end of the clavicle. There is tenderness in the region between the acromion and the lateral end of the clavicle and pain when abducting the right arm up to or above the level of the shoulder. Anteroposterior (AP) radiographs show that the acromioclavicular and coracoclavicu- lar spaces in the right shoulder are each more than 50% wider than the corresponding spaces in the left shoulder. Which injury is MOST indicated by the history, physical exam, and radio- graphs? A. acromioclavicular joint B. acromioclavicular joint subluxation C. acromioclavicular D. dislocation E. sternoclavicular joint dislocation

1 Lab 8—Joints of Upper/Lower Limb Acromioclavicular Joint– Answers

1. Answer D. (2) The point of the shoulder is the lat- eral-most limit of the shoulder. The acromion of the scap- ula lies directly beneath the skin here and thus gives the point of the shoulder its shape. Downward blows on the point of the shoulder the fibrous structures that sus- pend the scapula from the clavicle, in particular, the cap- sule of the acromioclavicular joint (AC) and the coracocla- vicular ligament (CL) . The severity of a shoulder separa- tion is assessed by comparing the widths of the acromio- clavicular and coracoclavicular spaces in an AP radio- graph of the injured shoulder with the widths of the corre- sponding spaces of the uninjured shoulder.

2. Answer A. (2) The point of the shoulder is the lat- eral-most limit of the shoulder. The acromion of the scap- ula lies directly beneath the skin here and thus gives the point of the shoulder its shape. Downward blows on the point of the shoulder strain the fibrous structures that sus- pend the scapula from the clavicle, in particular, the cap- sule of the acromioclavicular joint (AC) and the coracocla- vicular ligament (CL). The severity of a shoulder separa- tion is assessed by comparing the widths of the acromio- clavicular and coracoclavicular spaces in an AP radio- graph of the injured shoulder with the widths of the corre- sponding spaces of the uninjured shoulder.

3. Answer C. (2) A simple sprain of the acromioclavic- ular joint capsule is called a Grade I shoulder separation. In such an injury, the capsule sustains minimal tearing, and an AP radiograph of the injured shoulder shows nor- mal acromioclavicular and coracoclavicular spaces with- out deformity. A subluxation (partial dislocation) of the acromioclavicular joint is called a Grade II shoulder sepa- ration. It results from a significant rupture of the acromio- clavicular joint capsule. An AP radiograph of the injured shoulder shows an acromioclavicular space whose width is at least 50% greater than that of the uninjured shoulder. Inspection of the injured shoulder generally shows the lateral end of the clavicle a step above the acromion. A dislocation of the acromioclavicular joint is called a Grade III shoulder separation. It occurs when both the acromio- clavicular joint capsule and the coracoclavicular ligament are significantly ruptured. An AP radiograph of the injured shoulder shows acromioclavicular and coracoclavicular spaces at least 50% wider than those of the uninjured shoulder. Inspection of the injured shoulder commonly shows the acromion displaced anteroinferiorly to the lat- eral end of the clavicle.

2 Lab 8—Joints of Upper/Lower Limb Shoulder Joint — QuesƟons 1 of 1

1. The origination of the rotator cuff muscles is on this 5. A patient has a torn rotator cuff of the shoulder joint as . the result of an automobile accident. Which of the follow- A. ing muscle tendons is intact and has normal function? B. A. Supraspinatus C. Humerus B. Subscapularis D. Scapula C. Teres major E. Clavicle D. Teres minor E. Infraspinatus

2. The shoulder or pectoral girdle is formed by the scapu- lae and and is completed in front by the manu- brium of the sternum. How many muscles are included in the musculotendinous (rotator) cuff of the shoulder joint? A. 6 B. 5 C. 4 D. 3 E. 7

3. You are evaluating a radiograph of the only bony artic- ulation between the and the trunk. Which of the following joints are you evaluating? A. Glenohumeral B. Acromioclavicular C. Humeroclavicular D. Coracoclavicular E. Sternoclavicular

4. You are explaining the anatomy of the shoulder to a young athlete who has sustained an injury to one of his shoulders. You tell him that the chief stability to this joint is from which of the following? A. Glenohumeralligaments B. Acromioclavicular ligament C. Rotator cuff muscles D. Coracoclavicular E. Coracohumeral ligament

3 Lab 8—Joints of Upper/Lower Limb Shoulder Joint — Answers

1. Answer D. (2) The rotator cuff muscle stabilizes the 5. Answer C. (1) The rotator cuff consists of the ten- head of the humerus in the glenoid cavity of the scapula. dons of the supraspinatus, infraspinatus, subscapularis, To do so, they must originate from the scapula and insert and teres minor muscles. It stabilizes the shoulder joint by on the humerus. holding the head of the humerus in the glenoid cavity dur- ing movement. The teres major inserts on the medial lip of the intertubercular groove of the humerus.

2. Answer C. (2) The capsule of the shoulder joint is thin and has little mechanical strength. As the supraspina- tus, infraspinatus, teres minor and subscapularis pass to their insertions, they blend with the shoulder joint capsule and with each other, thus forming a musculotendinous cuff. This cuff, which is also called the rotator cuff, is in- complete only below and provides the major strength of the shoulder joint. The four component muscles keep the head of the humerus in place and are important fixators in various movements of the shoulder.

3. Answer E. (11) The upper limb is attached to the trunk only at the sternoclavicular joint. The primary attach- ment is muscular.

4. Answer C. (11) The primary stability to the gleno- humeral joint is provided by the tendons of the rotator cuff.

4 Lab 8—Joints of Upper/Lower Limb Joint—QuesƟons 1 of 1

1. An 18-month-old girl is brought to urgent care by her mother for evaluation of a painful right arm. The mother had been shopping with her toddler earlier that day and was holding her child's right when the child saw a toy that she liked; the child started pull- ing her mom in the direction of the toy. The mother pulled back on the child's hand, and that is when the toddler started screaming. On examination you note a well-developed, well-nourished 18- month-old girl. She is tearful and cries when you touch her right elbow or try to move her . A complete survey of the rest of her body reveals no evidence of other trauma. This history is most consistent with what injury? A. Nursemaid's elbow B. Colles' fracture C. Fracture of the scaphoid D. Fracture of the ulnar shaft E. Fracture of the distal radius

5 Lab 8—Joints of Upper/Lower Limb Elbow Joint—Answers

1. Answer A. (2) (Nursemaid's elbow (annular ligament dis- placement or radial head subluxation) is usually caused by an adult pulling or yanking on the outstretched arm of a toddler. The radial head slips through the annular ligament, which is then displaced towards the elbow joint. The child will usually hold the elbow partial- ly flexed and will refuse to move the arm. Reduction can readily be carried out by supination and extension of the forearm followed by full flexion of the forearm. This restores the annular ligament back to its normal anatomical position. Immobilization is not necessary and usually the child regains normal use of the joint within 20 minutes. Another maneuver called the pronation maneuver or handshake maneuver is also used. The history in this question is classic for Nursemaid's elbow. There is nothing to indicate a fracture of the scaphoid, distal radius (Colle's fracture), or ulnar shaft. Colle's fracture is a fracture of the distal radius and classically occurs after a fall on an outstretched hand.

6 Lab 8—Joints of Upper/Lower Limb Joint—QuesƟons 1 of 1

1. A 19-year-old construction worker sustains a superficial 5. You are examining a radiograph of a patient's wrist and laceration of the anterior wrist just proximal to the thenar note malalignment (dislocation) of one of the carpal and hypothenar eminences. Sensation is intact. Which of . Which of the following is most likely to be the dis- these tendons has most likely been severed? located carpal bone? A. Extensor carpi ulnaris A. Scaphoid B. Flexor digitorum profundus B. Lunate C. Flexor digitorum superficialis C. Triquetrum D. Flexor pollicis longus D. Capitate E. Palmaris longus E. Hamate

2. A 17-year-old male falls on his wrist while playing bas- 6. A patient with a severe tear of the medial collateral liga- ketball. After taking a history, you notice on physical exam ment of the wrist would likely display which of the follow- that he has marked tenderness within the "anatomical ing increased wrist movements? snuff box." What is the likely diagnosis? A. Flexion A. Fracture of the hook of the B. Extension B. Fracture of the C. Abduction C. Fracture of the D. Adduction D. Tendonitis E. Wrist sprain

3. A 23-year-old accountant trips over a briefcase and 7. A 20-year-old man presents with a left wrist injury. He falls onto his outstretched hand. A carpal bone fracture is says that he fell on his outstretched left arm two weeks ago suspected. Which of the following bones is most likely while playing basketball. On examination, he has tender- fractured? ness in the left anatomical snuff box. The physician is con- A. Scaphoid cerned that there could be a proximal fracture of the scaph- B. Lunate oid. C. Triquetrum What is the most likely consequence of an untreated proxi- D. Pisiform mal fracture of the scaphoid? E. Capitate A. Avascular necrosis B. Hyperplasia of the connective tissues surrounding the scaphoid C. Hypertrophy of the connective tissues surrounding the scaphoid D. Inability to oppose the thumb E. Inflammation leading to osteomyelitis

4. A 24-year-old man presents with pain in his right wrist that resulted when he fell hard on his outstretched hand. Radiographic studies indicate an anterior dislocation of a proximal row carpal bone that articulates with the most lateral proximal row carpal bone. Which of the following bones was dislocated? A. Capitate B. Lunate C. Scaphoid D. Trapezoid E. Triquetrum

7 Lab 8—Joints of Upper/Lower Limb Wrist Joint—Answers

1. Answer E. (3)The most superficial of the above ten- 5. Answer B. (11) The lunate bone is the most fre- dons is the palmaris longus (E). The extensor carpi ul- quently dislocated carpal bone. naris (A) is not on the anterior wrist. The flexor digitorum profundus (B), flexor digitorum superficialis (C), and flexor pollicis longus (D) tendons are all in the carpal tunnel, and are thus covered by the flexor retinaculum, whereas the palmaris longus is not.

2. Answer C. (3) The anatomical snuff box is the trian- 6. Answer C. (11) The medial or ulnar collateral liga- gular space formed by the extensor pollicis longus ment limits abduction or radial deviation of the wrist, (medial border), extensor pollicis brevis & abductor polli- which would increase if the ligament were severely torn. cis longus (lateral border), and the distal radial styloid. The and scaphoid bones form the floor or base of the snuff box. Tenderness in the anatomical snuffbox indicates scaphoid fracture until proven otherwise!

3. Answer A. (11) The scaphoid bone is the most fre- 7. Answer A. Avascular necrosis (10) Scaphoid is the quently fractured carpal bone. most commonly fractured carpal bone. It can be injured by a person hitting something with the knuckles of a clenched fist. An untreated proximal fracture of the scaph- oid can lead to avascular necrosis of the proximal frag- ment. This complication is due to the organization of blood supply to the scaphoid. Most of the blood supply to the scaphoid enters distally.

The proximal part of the scaphoid has no blood vessels entering it, depending instead on vessels that pierce the mid-portion of the bone. Arthritis can also occur as a long term complication. Answers B and C: Hyperplasia and hypertrophy of the connective tissues are not common complications of a scaphoid fracture. Answer D: Though a scaphoid fracture can lead to long term decreased range 4. Answer B. (3) The lunate is in the proximal row and of motion, the ability to oppose to thumb itself is not an articulates with the scaphoid laterally (this being the most isolated complication. Answer E: Osteomyelitis is an in- lateral of the proximal row). The lunate is the most com- fection within the bone. Scaphoid fracture does not carry monly dislocated carpal bone. It is usually displaced ante- an increased risk of this complication. Bottom Line: Un- riorly by rotation on its proximal, convex surface (where it treated proximal fracture of the scaphoid can lead to articulates with the radius). The displaced bone may com- avascular necrosis. press the median nerve in the carpal tunnel, leading to pain, sensory loss, and/or paralysis.

8 Lab 8—Joints of Upper/Lower Limb Joint —QuesƟons 1 of 1

1. A 72-year-old woman with Parkinson's disease has fallen down in the bathtub at her home and suffered a dislocation of the hip joint that may result in avascular necrosis of the femoral head and because of injuries to the arteries. Which of the following arteries might re- main intact? A. Lateral femoral circumflex artery B. Medial femoral circumflex artery C. Obturator artery D. Inferior gluteal artery E. Deep iliac circumflex artery

2. In a patient who has a posterior dislocation of the hip, which of the following ligamentous structures would be torn? A. Pubofemoral ligament B. C. Ischiofemoralligament D. Lacunar ligament E. Sacrotuberous ligament

3. A 54-year-old man has just dislocated his right hip. The physician is concerned about the integrity of the joint's blood supply. Which artery supplies most of the blood supply to the hip joint? A. Lateral circumflex femoral B. Medial circumflex femoral C. Superficial circumflexiliac D. Deep circumflexiliac E. Perforating

4. A patient with a is also exhibiting weak- ness of extension of the at the hip. This would indi- cate possible damage to which of the following? A. Femoral nerve B. Obturator nerve C. Common fibular portion of the sciatic nerve D. Tibial portion of the sciatic nerve E. Saphenous nerve

9 Lab 8—Joints of Upper/Lower Limb Hip Joint — Answers

1. Answer E. (5) The deep iliac circumflex artery does not supply the hip joint. However, this joint receives blood from branches of the medial and lateral femoral circum- flex, superior and inferior gluteal, and obturator arteries.

2. Answer C. (11) Posterior dislocation of the hip would tear the , thus reinforcing the capsule of the hip posteriorly.

3. Answer B. (11) The chief blood supply to the hip is the medial circumflex femoral artery.

4. Answer D. (11) Most of the extensor muscles of the hip (the hamstrings) are innervated by the tibial portion of the sciatic nerve. The gluteus maximus muscle, innervat- ed by the inferior gluteal nerve, could still weakly extend the thigh at the hip.

10 Lab 8—Joints of Upper/Lower Limb Joint —QuesƟons 1 of 2

1. A boy playing soccer has suffered trauma to the medial 5. A patient is unable to prevent anterior displacement of from a blow to the lateral aspect of the knee. the on the when the knee is flexed. Which of The knee is unstable. What other structure is most likely the following ligaments is most likely damaged? to be injured? A. Anterior cruciate B. Fibular collateral A. C. Patellar B. D. Posterior cruciate C. Anterior cruciate ligament E. Tibial collateral D. Patellar ligament E. Fibular collateral ligament

2. Your patient has sustained an external force to the 6. A high school football player suffers a traumatic knee injury knee. Which of the following ligaments has prevented ab- after an opposing player dives into the lateral aspect of his knee. duction of the leg at the knee? Which structure(s) in the knee are most vulnerable in such an A. Oblique popliteal injury? A. Anterior cruciate ligament, medial collateral ligament, medial B. Anterior cruciate meniscus c. Posterior cruciate B. Anterior cruciate ligament, medial collateral ligament, posteri- D. Lateral collateral or cruciate ligament E. Medial collateral C. Anterior cruciate ligament, lateral collateral ligament, posteri- or cruciate ligament D. Anterior cruicate ligament, , posterior cruci- ate ligament E. Lateral collateral ligament, medial collateral ligament, posteri- or cruicate ligament

3. In this same patient, which of the following ligaments 7. During a football game, a player sustains a powerful prevented posterior displacement of the tibia on the fe- blow to the lateral side of his weight-bearing leg. He expe- mur? riences excruciating knee pain and is unable to walk. The three structures most likely to be injured are the A. Oblique popliteal A. anterior cruciate and lateral collateral ligaments and B. Anterior cruciate the lateral meniscus C. Posterior cruciate B. anterior cruciate and medial collateral ligaments and D. Lateral collateral the medial meniscus E. Medial collateral C. posterior cruciate and lateral collateral ligaments and the lateral meniscus D. posterior cruciate and medial collateral ligaments and the lateral meniscus E. posterior cruciate and medial collateral ligaments and medial meniscus

4. One week following a sexual encounter at a ski resort 8. While playing in a Super Bowl game, a 32-year-old pro- in Colorado, a young woman develops a painful, swollen fessional football player is tackled and his anterior cruci- knee joint. The emergency department physician sus- ate ligament is torn. If not injured, the anterior cruciate pects gonococcal arthritis and wants to confirm this by ligament of the knee joint: sending joint fluid for bacterial culture. He uses the stand- A. Becomes taut during flexion of the leg ard suprapatelIar approach and passes a needle from the B. Resists posterior displacement of the femur on the tibia lateral aspect of the thigh into the region immediately C. Inserts into the medial femoral condyle proximal to the . Through which of the following D. Helps prevent hyperflexion of the knee joint muscles does the needle pass? E. Is lax when the knee is extended A. Adductor magnus B. Gracilis C. lliacus D. Sartorius E. Vastus lateralis

11 Lab 8—Joints of Upper/Lower Limb Knee Joint — Answers

1. Answer C. (6) Blows to the lateral aspect of the 5. Answer D. (1) The posterior cruciate ligament is knee typically injure one or more of the components of the important because it prevents forward displacement of the "terrible triad:' The triad includes the medial collateral liga- femur on the tibia when the knee is flexed. The anterior ment, the medial meniscus, and the anterior cruciate liga- cruciate ligament prevents backward displacement of the ment. femur on the tibia.

2. Answer E. (11) Abduction of the leg at the knee is 6. Answer A. (3) A common injury resulting from lateral- limited by the medial or tibial collateral ligament. to-medial knee trauma is injury to the "O'Donoghue tear," or "Unhappy Triad", which consists of the medial collat- eral ligament, the lateral meniscus, and the anterior cruci- ate ligament.

3. Answer C. (11) Posterior displacement of the tibia 7. Answer B. (4) The anterior cruciate and medial col- on the femur is limited by the PCL. lateral ligaments and the medial meniscus are sometimes called the "unhappy triad;' because they are commonly injured in lateral blows to the knee that forcefully abduct the tibia. A good mnemonic is "MAMM" (for Medial collat- eral, Anterior cruciate, and Medial Meniscus). Damage to the anterior cruciate ligament is characterized by the abil- ity to push the tibia too far forward on the femur. Damage to the lateral collateral ligaments and lateral menisci are very uncommon (choices A and C) and would be ex- pected if the tibia were forcefully adducted. Damage to the posterior cruciate ligaments (choices C, D, E) is ex- tremely rare and is characterized by the ability to push the tibia too far backward on the femur.

4. Answer E. (4) This route passes through the vastus 8. Answer B. (5) The anterior cruciate ligament of the lateralis to penetrate the knee joint via the suprapatellar knee joint prevents posterior displacement of the femur bursa, allowing aspiration of joint fluid for culture. The on the tibia and limits hyperextension of the knee joint. vastus lateralis, together with the vastus medialis, vastus This ligament becomes taut when the knee is extended intermedius, and rectus femoris, forms the quadriceps and lax when the knee is flexed. It inserts into the lateral muscle. The adductor magnus (choice A) is on the inner femoral condyle posteriorly within the intercondylar notch. and anterior aspect of the upper thigh. The gracilis (choice B) is on the inner aspect of the thigh. The iliacus (choice C) is mostly in the false . The sartorius (choice D) passes diagonally from the lateral hip to the medial knee.

12 Lab 8—Joints of Upper/Lower Limb Knee Joint —QuesƟons 2 of 2

9. During a sports medicine physical by a local family phy- 13. A 22-year-old man who belongs to a weekend football league was sician, a young woman is tested for stability of her joints running with the ball when a defender tackled him mid-lower limb from the side. After the tackle, he felt that his knee was hurt and went to the before try-outs for the high school team. Which of the fol- emergency room. From the MRI of the knee shown below, the lateral lowing ligaments is important in preventing forward dis- meniscus is uniformly black; however, the medial meniscus has a tear placement of the femur on the tibia when the weight- (lucent area within the meniscus). Which of the following is the reason bearing knee is flexed? why the medial meniscus is more susceptible to damage than the A. Medial meniscus lateral meniscus? A. The medial meniscus is attached to the popliteus muscle tendon, B. Tibial collateral ligament which can move into a position making it more susceptible C. Fibular collateral ligament B. The medial meniscus is attached to the medial (tibial) collateral D. Posterior cruciate ligament ligament, which holds it relatively immobile, making it more susceptible E. Anterior cruciate ligament C. The medial meniscus is attached to the anterior cruciate ligament, which holds it relatively immobile, making it more susceptible D. The only reason the medial meniscus is more susceptible to dam- age is that the knee usually gets hit laterally, causing more torsion on the medial meniscus

10. A high school football player suffers a traumatic knee 13. injury after an opposing player dives into the lateral as- pect of his knee. Which structure(s) in the knee are most vulnerable in such an injury? A. Anterior cruciate ligament, medial collateral ligament, medial meniscus B. Anterior cruciate ligament, medial collateral ligament, posterior cruciate ligament C. Anterior cruciate ligament, lateral collateral ligament, posterior cruciate ligament D. Anterior cruicate ligament, medial meniscus, posterior cruciate ligament E. Lateral collateral ligament, medial collateral ligament, posterior cruicate ligament

11. You have examined a patient and find that there is 14. A college rugby player is brought to the student health weakness in the ability to flex the knee. This indicates a clinic after sustaining a knee injury during practice. He problem with which of the following nerves? says he landed with a planted knee and was accidentally A. Femoral nerve kicked by another player. On examination of the injured B. Tibial nerve knee, the tibia is displaced anteriorly from the femur in the C. Common fibular nerve flexed position, there is laxity of the knee with valgus D. Deep fibular nerve stress at 0 degrees of flexion, and a "click" is heard when E. Superficial fibular nerve the patient's knee is externally rotated and passively ex- tended from 90 degrees to 0 degree. Which of the follow- ing set of structures is most likely damaged as a result of this injury?

A. Lateral collateral ligament, lateral meniscus, posterior cruciate ligament B. Lateral collateral ligament, medial meniscus, anterior cruciate ligament 12. A 78-year-old woman receives knee surgery because C. Medial collateral ligament, lateral meniscus, posterior her lateral meniscus is torn. Before injury, the normal lat- cruciate ligament eral meniscus of the knee joint: D. Medial collateral ligament, medial meniscus, anterior A. Is C-shaped or forms a semicircle cruciate ligament B. Is attached to the fibular collateral ligament E. Medial collateral ligament, medial meniscus, posterior C. Is larger than the medial meniscus cruciate ligament D. Lies outside the synovial cavity E. Is more frequently torn in injuries than the medial me- niscus

13 Lab 8—Joints of Upper/Lower Limb Knee Joint — Answers

9. Answer D. (5) The posterior cruciate ligament pre- 13. Answer B. (7) The medial meniscus is attached to vents forward displacement of the femur on the tibia when the medial (tibial) collateral ligament, which holds it rela- the knee is flexed. The anterior cruciate ligament prevents tively immobile, making it more susceptible. It is relatively backward dislocation of the femur on the tibia when the immovable and, therefore, unable to evade damage such knee is extended. The medial meniscus acts as a cush- as occurred in this case. The medial meniscus is clearly ion, or shock absorber, and forms a more stable base for not attached to the popliteus muscle (answer a) nor to the the articulation of the femoral condyle. The tibial and fibu- anterior cruciate ligament (answer c). The knee usually lar collateral ligaments prevent medial and lateral dis- gets hit laterally, causing more torsion on the medial me- placement, respectively, of the two long bones. niscus (answer d), making this the second best answer.

10. Answer A. (3) A common injury resulting from lat- eral-to-medial knee trauma is injury to the "O'Donoghue tear," or "Unhappy Triad", which consists of the medial collateral ligament, the lateral meniscus, and the anterior cruciate ligament.

11. Answer B. (11) The muscles that flex the knee are 14. Answer D. The MCL tears when the knee is bent innervated by the tibial portion of the toward the midline, extending the distance between the sciatic nerve. medial condyles of the femur and tibia. The ACL is stretched beyond its limit in a forceful lateral superior sur- face of the tibia that tears during a lateral knee injury be- cause of its intimate association with the MCL; the deep portion of this ligament is actually attached to the medial meniscus. Although the vignette correctly describes the unhappy triad presentation, it is important to note that the triad itself is very rare, and a more common pathology associated with acute, isolated ACL tears is injury to the lateral, not the medial, meniscus. A lateral knee impact may cause damage to the classic "unhappy triad" (MCL, medial meniscus, and ACL).

12. Answer D. (5) The lateral meniscus, like the medial meniscus, lies outside the synovial cavity but within the joint cavity. However, the lateral meniscus is nearly circu- lar, whereas the medial meniscus is C-shaped or forms a semicircle. The lateral meniscus is smaller than the medi- al meniscus and less frequently torn in injuries than the medial meniscus. In addition, the lateral meniscus is sep- arated from the fibular collateral ligament by the tendon of the popliteal muscle, whereas the medial meniscus at- taches to the tibial collateral ligament.

14 Lab 8—Joints of Upper/Lower Limb Joint —QuesƟons 3 of 4

1. A woman wearing high heels has fallen and twisted her ankle. Part of which ligament was most likely stretched? A. Deltoid ligament B. Medial ligament C. Plantar calcaneonavicular ligament D. Lateral ligament E. Long plantar ligament

2. A 23-year-old woman wearing high-heeled shoes in- verts and her ankle while running down a flight of stairs. Which of the following ligaments did she most likely injure? A. Anterior talotibial B. Calcaneofibular C. Calcaneotibial D. Deltoid E. Medial collateral

3. You are concerned that your patient's medial deltoid ligament may have been torn from its proximal attach- ment. Which of the following would you palpate for ten- derness? A. The medial aspect of the tibial shaft B. The lateral aspect of the fibular shaft C. The lateral malleolus D. The medial malleolus E. The calcaneus

4. When will a patient's ankle joint have the greatest sta- bility? A. When the knee is flexed B. When the is dorsiflexed C. When the foot is plantarflexed D. When the foot is everted E. When the foot is inverted

15 Lab 8—Joints of Upper/Lower Limb Knee Joint — Answers 4 of 4

1. Answer D. (6) Most ankle sprains are inversion sprains, which tear a component of the lateral ligament. The deltoid or medial ligament supports the medial side of the ankle. The plantar calcaneonavicular ligament helps maintain the medial longitudinal arch of the foot; the long plantar ligament helps maintain the lateral longitudinal arch of the foot.

2. Answer B. (4) The most common type of ankle sprain is lateral, which occurs as a result of excessive inversion of the foot and plantar flexion of the ankle. The calcaneofibular (not calcaneotibial [choice C]) and anteri- or talofibular (not talotibial [choice A]) ligaments may tear, producing marked swelling and pain. These two ligaments combined with the posterior talofibular ligament constitute the lateral ligament of the ankle. The deltoid ligament (choice D), also known as the medial ligament of the an- kle, is a very strong, thick structure located at the medial malleolus. Excessive eversion would be the most likely mechanism of injury. The medial collateral ligament (choice E) is damaged in lateral blows to the knee.

3. Answer D. (11) The four components of the deltoid ligament arise from the medial malleolus.

4. Answer B. (11) The talocrural or ankle joint proper has the greatest stability in dorsiflexion.

16