📚 Question Bank

Correct Answer: B

Opposition is the defining movement that allows humans to pinch and manipulate tools.

For the pad of the thumb to touch the pad of the pinky finger, it isn't enough to just bring the thumb across the palm (flexion/abduction). The first metacarpal bone must physically spin or rotate medially on its longitudinal axis to turn the thumb pad inward.

Correct Answer: C

Think about doing a handstand. The massive force from the floor enters your hand and transfers almost entirely to the wide distal end of the RADIUS. However, at the elbow, it is the ULNA that has the massive, strong articulation with the humerus.

The fibers of the interosseous membrane run obliquely downward from the radius to the ulna. This clever design catches the force traveling up the radius and shunts it across the membrane to the ulna, which then securely transfers the load to the humerus.

Correct Answer: A

The UCL has three parts: anterior, posterior, and transverse. The anterior bundle is the thickest, strongest, and most biomechanically critical.

When a baseball pitcher throws, enormous valgus (outward-bending) stress is placed on the inner elbow. The anterior bundle of the UCL is the primary structure preventing the elbow from gapping open on the medial side. Rupture of this bundle necessitates 'Tommy John' reconstructive surgery.

Correct Answer: C

Rheumatoid arthritis causes chronic synovitis (inflammation of the joint lining). Over time, this inflammation stretches out and destroys the soft tissue restraints of the joint, specifically the radial collateral ligaments and the joint capsules of the knuckles (MCP joints).

Once the radial support is gone, the powerful flexor and extensor tendons naturally pull the fingers into a severe ulnar drift.

Correct Answer: C

The wrist isn't just one hinge; it's a complex system. The midcarpal joint is the functional joint space that lies between the proximal row of carpal bones (scaphoid, lunate, triquetrum) and the distal row (trapezium, trapezoid, capitate, hamate).

A significant portion of your total wrist flexion and extension actually occurs at this midcarpal joint, not just at the radius.

Correct Answer: B

The long head of the biceps tendon takes a 90-degree turn as it exits the shoulder joint and runs down the bicipital groove of the humerus.

To prevent the tendon from bowing out or popping out of the groove when the muscle contracts, a broad band of tissue called the transverse humeral ligament roofs over the groove, acting like a seatbelt. If this tears, the tendon will painfully subluxate (snap out).

Correct Answer: D

When your arms are resting down by your sides (adducted), gravity wants to pull the heavy humerus straight down out of the socket.

The primary static structure fighting gravity in this resting position is the coracohumeral ligament. It acts as a strong suspensory sling extending from the coracoid process to the greater and lesser tubercles.

Correct Answer: B

Guyon's canal is a small tunnel on the pinky-side of the wrist. Its lateral wall is formed by the bony hook of the hamate.

The ulnar nerve and ulnar artery pass directly through this canal to enter the hand. If a golfer or baseball player takes a hard swing and fractures the hook of the hamate, the bone fragments or swelling will compress these structures, causing numbness in the ring and little fingers.

Correct Answer: D

It's an amazing biomechanical fact: your entire arm and shoulder blade are attached to your body's main skeleton by just one small joint.

The sternoclavicular (SC) joint is the sole bony strut connecting the clavicle to the sternum. Everything else (the scapula on the ribs) is held on purely by muscular slings. This is why the ligaments of the SC joint are incredibly strong—dislocations here are rare and require massive force.

Correct Answer: D

PLRI is the most common pattern of chronic elbow instability. It occurs when a specific band on the outside of the elbow—the Lateral Ulnar Collateral Ligament (LUCL)—is compromised.

The LUCL normally acts like a sling holding the radial head in place. When it fails, axial load and supination cause the radius and ulna to twist away (subluxate posterolaterally) from the humerus, leading to a catching or giving-way sensation.

Correct Answer: A

Just like the knee, the elbow has a subtle locking mechanism to maximize stability when fully straight.

As the olecranon process of the ulna slams into the olecranon fossa of the humerus at terminal extension, the slightly asymmetric shape of the trochlea forces the ulna to slightly externally rotate (abduct). This firmly impacts the bony surfaces together, locking the joint into a rigid structure.

Correct Answer: C

The scaphoid and lunate bones are tightly bound together. Normally, the scaphoid wants to flex forward, and the triquetrum wants to extend backward, with the lunate caught in the middle balancing them.

If the scapholunate ligament tears, the scaphoid falls forward unattached. The lunate, now completely under the control of the triquetrum, tilts backward (Dorsally). This creates a Dorsal Intercalated Segment Instability (DISI) pattern visible on an X-ray.

Correct Answer: A

The rotator cuff isn't a continuous ring; there is a gap between the front muscle (subscapularis) and the top muscle (supraspinatus). This gap is the rotator interval.

To prevent the shoulder from simply falling out of this gap, the joint capsule here is highly thickened by two key ligaments: the coracohumeral ligament and the superior glenohumeral ligament. The long head of the biceps tendon also exits the joint through this interval.

Correct Answer: A

Arthrokinematics deals with the microscopic movements of joint surfaces. When you raise your arm out to the side (abduction), the large humeral head rolls upward (superiorly) on the glenoid.

If it only rolled, it would quickly crash into the bony acromion roof above it. To prevent this impingement, the rotator cuff muscles pull the humeral head downward, forcing it to slide (glide inferiorly) as it rolls superiorly, keeping it centered in the socket.

Correct Answer: D

Forearm fractures rarely happen in isolation because the radius and ulna are tightly bound into a rigid ring by ligaments. If one bone breaks significantly, a joint usually blows out to relieve the pressure.

A Galeazzi fracture is a fracture of the distal radius shaft accompanied by a tear of the TFCC and a dislocation of the Distal Radioulnar Joint (DRUJ). (A Monteggia fracture is the proximal counterpart: proximal ulna fracture + radial head dislocation).

Correct Answer: B

While several ligaments wrap the thumb base, the anterior oblique ligament (commonly called the 'beak ligament' because it attaches to the volar beak of the metacarpal) is the linchpin of stability.

It acts as the primary check against the metacarpal sliding backward (dorsal subluxation) during forceful pinch grips. Degeneration of this specific ligament is the primary initiating event in severe thumb base osteoarthritis.

Correct Answer: B

Frozen shoulder involves severe, painful stiffening of the shoulder capsule. The pathology usually begins with intense inflammation and subsequent fibrotic scarring in the anterosuperior capsule—specifically the rotator interval and the coracohumeral ligament.

Because these structures normally limit external rotation, their severe contracture results in the classic clinical hallmark of frozen shoulder: a near-complete inability to passively externally rotate the arm.

Correct Answer: C

Arm elevation is a symphony of joint movements. To get your arm straight up (180 degrees), the glenohumeral joint provides about 120 degrees, and the scapula must upwardly rotate 60 degrees.

However, the scapula is attached to the clavicle. To allow the scapula to tip upward that far, the clavicle must physically twist backward (posterior axial rotation) at the sternoclavicular joint by about 30 degrees. If the clavicle is pinned (e.g., by a plate), full arm elevation is impossible.

Correct Answer: B

Normally, the distal end of the ulna is slightly shorter or perfectly level with the distal radius (neutral variance).

In positive ulnar variance, the ulna is relatively too long. This causes the bony tip of the ulna to abnormally smash into the TFCC cushion and the lunate bone during gripping and rotation. Over time, this chronic pounding leads to cartilage wear (chondromalacia) and osteoarthritis on the ulnar side of the wrist.

Correct Answer: B

The strong palmar radiocarpal ligaments form a V-shape on the front of the wrist, leaving a distinct gap in the fibrous capsule right over the joint between the lunate and the capitate. This weak spot is the space of Poirier.

During a massive hyperextension injury (like a car crash), the capitate bone can blast right through this weak spot, resulting in a devastating perilunate dislocation.

Correct Answer: D

In the foot, the Lisfranc joint forms the rigid, unmoving arch of the midfoot. The hand has a similar architectural core.

The 2nd and 3rd metacarpals interlock deeply with the trapezoid and capitate bones to form a highly rigid, immobile central pillar. The rest of the hand (the thumb on one side, and the mobile 4th/5th digits on the other) moves around this stable central post to allow for powerful grasping.

Correct Answer: C

The oblique cord is a small, inconsistent fascial band near the elbow. Unlike the main interosseous membrane (which runs downward from radius to ulna to transmit force), the oblique cord runs in the opposite direction (downward from ulna to radius).

Because of this orientation, it tightens when the radius spins outward, acting as a minor secondary restraint to limit extreme over-supination.

Correct Answer: C

The MCP joints (knuckles) are very stable in extension, but they can be bent backward violently. To prevent this hyperextension, the palmar side of the joint is reinforced by a thick, rigid pad of fibrocartilage called the volar plate.

If a finger is bent too far back, the volar plate tears at its proximal attachment, allowing the base of the phalanx to dislocate dorsally over the metacarpal head.

Correct Answer: D

Surgeons want to find natural gaps between muscles (internervous planes) to avoid cutting nerves. The 'Kocher approach' to the lateral elbow exploits the gap between the anconeus muscle (supplied by the radial nerve) and the extensor carpi ulnaris (ECU, supplied by the posterior interosseous nerve).

Spreading these two muscles apart provides a safe, bloodless window directly down to the radial head and lateral ligaments.

Correct Answer: A

Ribs are classified based on their anterior attachment:

• True ribs (1-7): Attach directly to the sternum via their own individual costal cartilages.
• False ribs (8-10): Their cartilages attach to the cartilage of the rib above them, not directly to the sternum.
• Floating ribs (11-12): Have no anterior attachment at all; they end in the abdominal musculature.