Prime Movers & Power Players
This muscle is the primary contributor to hip extension during sit-to-stand and is essential for generating power in older adults.
Gluteus Maximus
Damage to this nerve would most likely result in inability to extend the knee and difficulty rising from a chair.
Weakness of this muscle results in contralateral pelvic drop during single-leg stance and contributes to a Trendelenburg gait pattern.
Gluteus Medius
A patient demonstrates decreased foot clearance during swing phase and compensates with excessive hip flexion. Weakness of this muscle is MOST likely responsible.
Anterior Tibialis
This muscle originates from the anterior superior iliac spine, crosses both the hip and knee, and assists in hip flexion, abduction, and external rotation.
Sartorius
A 73-year-old patient demonstrates difficulty maintaining an upright posture and reports fatigue when attempting to extend the trunk during standing and walking. Which primary muscle group is MOST responsible for producing spinal extension in this task?
Erector Spinae
Injury to this nerve results in wrist drop.
This deep abdominal muscle is critical for spinal stabilization and core activation.
Transverse Abdominis
This compensation reduces demand on weak hip abductors during walking.
Trunk lean toward the stance limb
This muscle flexes the elbow and supinates the forearm.
Biceps Brachii
This muscle group generates the majority of push-off power during gait.
Plantarflexors
This nerve is responsible for most intrinsic hand muscle innervation.
Ulnar Nerve
Weakness of this muscle contributes to scapular winging.
Serratus Anterior
Knee valgus during a squat is MOST associated with weakness of these muscles.
This muscle elevates the scapula and contributes to neck side bending.
Levator Scapulae
This shoulder muscle is responsible for abduction beyond the first 15 degrees.
Deltoid
This nerve is commonly associated with “foot drop” when injured.
Sciatic Nerve (deep fibular branch)
This deep spinal stabilizer plays a key role in segmental control of the lumbar spine.
Multifidus
A patient reports jaw fatigue and difficulty chewing tough foods. During examination, the patient demonstrates decreased ability to elevate the mandible and generate bite force. Weakness of which muscle is MOST likely responsible?
Masseter
This muscle originates on the anterior sacrum and inserts on the greater trochanter. It assists with hip external rotation and is clinically significant because it can compress the sciatic nerve, leading to radiating posterior leg symptoms.
Piriformis
During gait assessment, a 79-year-old patient demonstrates difficulty controlling knee flexion during loading response, resulting in a slight “collapse” of the limb immediately after heel strike. Weakness of which primary muscle is MOST responsible for this deficit?
Quadriceps
A 74-year-old female presents following a fall with her arm held in adduction and internal rotation. She demonstrates inability to abduct the shoulder or flex the elbow. This presentation is MOST consistent with injury to which part of the brachial plexus?
Superior Trunk (C5-C6) -- Erb's Palsy
A 72-year-old patient presents with a forward head and rounded shoulder posture. Examination reveals protracted scapulae and increased thoracic kyphosis. Which muscle is MOST likely weak and contributing to this postural presentation?
Rhomboid Major
A patient initiates shoulder abduction with a noticeable shoulder shrug and reports pain between 60–120 degrees. Which impairment BEST explains this movement dysfunction?
Supraspinatus weakness
A patient is asked to rotate their trunk to the left during a functional reaching task. Weakness of which muscle would MOST directly impair this movement?
Right External Obliques