How do you examine for muscle wasting on physical examination?

How to Examine for Muscle Wasting on Physical Examination

Systematically assess muscle wasting by examining the temporalis muscle, clavicle prominence, shoulder contour, scapula visibility, rib visibility, interosseous muscle mass, and quadriceps muscle mass, scoring each site on a 7-point scale where 1-2 indicates severe wasting, 3-5 indicates moderate wasting, and 6-7 indicates normal to mild wasting. 1, 2

Specific Anatomical Sites to Examine

Head and Upper Body

• Temporalis muscle: Palpate the temple area for muscle bulk and depression, which indicates wasting 1, 2
• Infraorbital fat pads: Observe the area directly below the eyes—normally appearing as a slight bulge in well-nourished individuals but appearing "hollow" in malnourished patients 1
• Clavicles: Assess prominence—increased visibility indicates muscle and fat loss 1, 2
• Shoulder contour: Evaluate the shape—rounded shoulders indicate adequate nutrition while squared-off shoulders indicate malnutrition 1, 2
• Scapula: Check for increased visibility of the shoulder blade, which suggests muscle wasting 1, 2

Trunk and Extremities

• Ribs: Assess visibility—prominent ribs indicate loss of intercostal muscle mass and subcutaneous tissue 1, 2
• Interosseous muscles: Examine the muscle mass between the thumb and forefinger—this area shows early wasting 1, 2
• Quadriceps muscle mass: Palpate the anterior thigh for bulk and tone 1, 2

Differentiating Fat Loss from Muscle Wasting

Assess subcutaneous fat separately by examining specific fat deposits to distinguish fat loss from true muscle wasting. 1

• Triceps and biceps skin fold: Gently pinch the skin above these muscles—the thickness of the fold between your fingers indicates nutritional status 1
• Fat pads should be assessed independently from muscle bulk to avoid misclassifying simple weight loss as muscle wasting 1

Standardized Scoring Approach

Use a 7-point scale for each anatomical site examined, then aggregate scores into a global assessment. 1, 2

• Scores of 1-2: Severe malnutrition/muscle wasting 1, 2
• Scores of 3-5: Moderate to mild malnutrition 1, 2
• Scores of 6-7: Mild malnutrition to normal nutritional status 1, 2

The global score is not a simple arithmetic average—weight the physical examination findings more heavily if they clearly indicate severe malnutrition, even if historical factors suggest otherwise 1

Functional Assessment to Complement Physical Findings

Incorporate functional muscle assessment alongside anatomical examination to evaluate the clinical significance of observed wasting. 2

• Gait assessment: Observe walking pattern for weakness or instability 2
• Gowers' sign: Test ability to rise from floor or chair without arm support 2
• Handgrip dynamometry: Quantify muscle strength in cooperative patients 1, 2
• Timed function tests: Measure time to complete specific tasks 2

Important Clinical Pitfalls

Do not rely on body weight or BMI alone, as these measurements cannot distinguish between fat mass and muscle mass loss. 1

• Patients may have normal or elevated BMI while experiencing significant muscle wasting (sarcopenic obesity) 1
• Fluid overload in conditions like kidney disease can mask muscle wasting when using weight-based assessments 1
• Edema can obscure physical examination findings of muscle wasting, making assessment more challenging 1

Training is essential for accurate assessment—the physical examination for muscle wasting requires practice and standardization to ensure reliability. 1

Advanced Assessment When Available

Consider ultrasound for more objective muscle mass measurement in hospitalized or critically ill patients, as it is not significantly affected by fluid shifts. 1, 2

• Ultrasound provides reliable bedside assessment even in non-collaborative patients 1
• CT scan at the L3 vertebra level can quantify skeletal muscle mass if already being performed for other clinical indications 1, 2
• Bioelectrical impedance analysis is unreliable in the presence of fluid overload 1