Unit 5: Mechanics of shoulder, spine and hip - Practice Quiz

1 Which joint is the main ball-and-socket joint of the shoulder complex?

2 The group of four muscles that stabilize the glenohumeral joint is known as the:

3 The shallow socket of the scapula that receives the humeral head is called the:

4 Raising the arm forward and upward in the sagittal plane is called:

5 The coordinated movement between the humerus and scapula during arm elevation is known as:

6 Moving the arm away from the midline of the body in the frontal plane is called:

7 Compressive loads on the glenohumeral joint generally increase when the arm is:

8 Which muscle is a major contributor to the compressive load at the glenohumeral joint during abduction?

9 Holding a heavy weight in the hand with the arm extended increases shoulder load mainly because it increases the:

10 How many vertebrae make up the typical human vertebral column (excluding fused sacral and coccygeal segments)?

11 The soft structure located between two adjacent vertebral bodies that acts as a shock absorber is the:

12 The gel-like central portion of an intervertebral disc is called the:

13 How many cervical vertebrae are present in the human spine?

14 Bending the trunk forward is an example of spinal:

15 Twisting the trunk to the left or right is termed spinal:

16 Which muscle group is the primary extensor of the spine?

17 Lifting a load with a rounded back rather than a straight back tends to:

18 The hip joint is classified as which type of synovial joint?

19 The socket of the pelvis that receives the head of the femur is called the:

20 During single-leg standing, the load on the hip joint is typically:

21 The shoulder complex consists of four articulations. Which of the following is a physiological (functional) joint rather than a true synovial joint?

22 The glenohumeral joint is inherently unstable because the glenoid fossa covers only a small portion of the humeral head. Which structure primarily deepens the socket to improve stability?

23 During full arm abduction to , the scapulohumeral rhythm describes the ratio of glenohumeral to scapulothoracic motion. What is the commonly accepted overall ratio?

24 A patient can only abduct the arm to about before further motion is blocked. Which movement is normally required to allow abduction beyond by clearing the greater tubercle from under the acromion?

25 When the arm is held horizontally in abduction, the deltoid must generate a large force. This is primarily because the muscle's line of action creates a short moment arm relative to the long external load arm of the outstretched limb, which requires the muscle to compensate for the mechanical disadvantage by producing forces several times body-segment weight.

26 The rotator cuff muscles are essential for stability during abduction primarily because they:

27 A typical intervertebral disc consists of a central gel-like core and a surrounding fibrous ring. Which component primarily resists compressive loads by generating hydrostatic pressure?

28 The normal adult spine has curves in the sagittal plane. Which of the following correctly pairs a region with its curve type?

29 In which region of the spine is axial rotation greatest, largely due to the orientation of the facet joints in the transverse/oblique plane?

30 The coupling of lateral bending with axial rotation is a characteristic motion of the spine. This phenomenon of two movements occurring together is best described as:

31 When lifting a load with the trunk flexed forward, the erector spinae muscles must generate very large forces. This is chiefly because these muscles have a:

32 Intra-abdominal pressure (IAP) is thought to help reduce spinal loading during lifting because it:

33 Nachemson's classic studies showed that intradiscal pressure in the lumbar spine changes with posture. Which position generally produces the highest L3 disc pressure?

34 The hip is classified as a ball-and-socket (spheroidal) joint. The depth and stability of its socket are enhanced by which fibrocartilaginous structure?

35 The angle of inclination of the adult femur (between the neck and shaft) is normally about . A pathological decrease in this angle is termed:

36 Which muscle group is the primary generator of hip extension and is especially active during activities like climbing stairs and rising from a squat?

37 During single-leg stance, the hip abductors must contract to keep the pelvis level. Because the abductor moment arm is short relative to the long moment arm of body weight, the resulting joint reaction force at the hip is approximately:

38 A patient with weak hip abductors on the stance leg exhibits a dropping of the pelvis on the opposite (swing) side during walking. This clinical sign is called:

39 Why does using a cane in the hand opposite to an affected hip reduce the hip joint reaction force more effectively than using it on the same side?

40 The subacromial space houses the supraspinatus tendon and subacromial bursa. Repeated compression of these structures during overhead activity, leading to pain, is commonly termed:

41 A person holds a weight in the hand with the arm abducted horizontally. The deltoid inserts at from the glenohumeral joint at an angle of to the humerus, and the center of mass of the arm () is at while the weight is at . Approximately what deltoid muscle force is required for equilibrium?

42 During of humeral elevation, the scapulohumeral rhythm is commonly described as . If the glenohumeral joint contributes its full expected share, how much scapular rotation occurs and what is the approximate glenohumeral contribution?

43 The glenoid labrum and negative intra-articular pressure both contribute to glenohumeral stability. Which statement best explains why labral removal disproportionately compromises stability in mid-range motion?

44 Considering the intervertebral disc as a hydrostatic structure, why does the nucleus pulposus lose its ability to distribute load evenly with age-related dehydration?

45 A worker lifts a box held anterior to the L5-S1 disc. The erector spinae act with a moment arm of . Neglecting body weight, estimate the muscle force and the approximate compressive load on the disc (assume muscle force acts roughly vertically).

46 Intra-abdominal pressure (IAP) is proposed to reduce spinal compression during lifting. Which mechanism best captures how IAP unloads the lumbar spine?

47 Using a simplified single-leg stance model, if body weight is , the weight supported (minus the stance leg, BW) acts at medial to the hip center, and the abductors act at lateral, what is the approximate joint reaction force at the hip?

48 The femoral neck-shaft angle averages about . In coxa valga (increased angle), how are the abductor moment arm and joint reaction force affected during single-leg stance?

49 During trunk flexion, the 'flexion-relaxation phenomenon' describes erector spinae EMG silence at full flexion. What structure primarily bears the flexion moment at this point, and what is the clinical risk?

50 Rotator cuff force is essential for the concavity-compression mechanism. During early abduction, why does supraspinatus dysfunction lead to superior humeral migration despite an intact deltoid?

51 The orientation of lumbar facet joints differs from cervical facets. How does the predominantly sagittal orientation of lumbar facets influence available motion and load resistance?

52 The 'setting phase' of scapulohumeral rhythm occurs in the first of elevation. What is the biomechanical significance of the variable scapular motion in this phase?

53 A cane held in the contralateral hand reduces hip joint load. If a cane provides a downward force of at from the stance hip while the abductors act at , by approximately how much does the cane reduce the required abductor force?

54 Why does the lever-arm disadvantage of the erector spinae make even moderate lifting produce disc compression far exceeding the external load?

55 Femoral anteversion averages ~–. In excessive anteversion, what compensatory gait pattern and biomechanical consequence typically arise?

56 Coupled motion in the cervical spine links lateral flexion with axial rotation. Below C2, to which side does the spinous process typically rotate during ipsilateral lateral flexion, and why?

57 The coracoacromial arch forms the roof of the subacromial space. Which combination of factors most increases the risk of mechanical impingement of the supraspinatus tendon?

58 Comparing standing, sitting unsupported, and lying supine, Nachemson's classic disc pressure studies showed which relative ordering of L3 intradiscal pressure?

59 During full elevation the humerus must externally rotate. What is the primary biomechanical reason external rotation is required to reach full overhead elevation?

60 The acetabular labrum contributes to hip stability and a fluid seal. How does labral loss primarily alter hip joint mechanics beyond reduced stability?