What is the typical ordering of longus, brevis, and magnus muscles in extremities?

Typical Ordering of Longus, Brevis, and Magnus Muscles in Extremities

In the human extremities, longus muscles are typically positioned more superficially or proximally, brevis muscles are positioned more distally or deeply, and magnus muscles (when present) are typically the largest in their respective muscle groups.

General Pattern in Muscle Naming

The naming convention for muscles in the extremities follows a logical anatomical pattern:

• Longus: Typically refers to the longer muscle in a group, often positioned more superficially or proximally
• Brevis: Typically refers to the shorter muscle in a group, often positioned more distally or deeply
• Magnus: Typically refers to the largest muscle in a group

Examples in Upper Extremities

Vertebral Region

• The vertebral artery V2 segment passes between the longus colli and scalenus anterior muscles 1

Hand/Wrist

• Extensor pollicis longus and extensor pollicis brevis - the longus inserts more distally on the distal phalanx while the brevis inserts on the proximal phalanx

Examples in Lower Extremities

Hip/Thigh

• Adductor group: Consists of adductor brevis, adductor longus, and adductor magnus 1
  • Adductor brevis: Positioned deeper and shorter
  • Adductor longus: More superficial and longer
  • Adductor magnus: The largest of the three adductors

Leg

• Peroneal muscles: Peroneus longus and peroneus brevis 2, 3

  • Peroneus longus: More superficial and longer course
  • Peroneus brevis: Deeper and shorter course

• Extensor hallucis: Extensor hallucis longus and extensor hallucis brevis 4

  • Extensor hallucis longus: Originates more proximally on the fibula
  • Extensor hallucis brevis: Originates more distally on the dorsum of the foot

Functional Implications

The positioning of these muscles has important functional implications:

1. Mechanical advantage: The different positions provide varying mechanical advantages for joint movements

   • For example, the adductor longus, brevis, and magnus work together in the transverse plane during gait, with EMG studies showing varied activity during different phases 5

2. Rehabilitation considerations: When designing rehabilitation programs, understanding the specific functions of these muscles is crucial

   • For example, selective training of peroneus longus versus peroneus brevis produces different effects on ankle strength and muscle morphology 2, 3

3. Clinical relevance: In cases of injury or pathology, understanding the specific muscle affected is important for diagnosis and treatment

   • For example, in tendon lacerations of the hallux, both extensor hallucis longus and brevis may be affected, requiring specific rehabilitation approaches 4

Common Pitfalls in Clinical Practice

• Misidentification: Failing to distinguish between longus and brevis muscles can lead to improper diagnosis and treatment
• Overgeneralization: Assuming all muscle groups follow the exact same pattern (some anatomical variations exist)
• Incomplete assessment: Not considering the functional relationship between longus, brevis, and magnus muscles in the same group

Understanding the typical ordering and anatomical relationships between longus, brevis, and magnus muscles is essential for accurate diagnosis, effective treatment planning, and optimal rehabilitation outcomes in musculoskeletal medicine.