Accessory semimembranosus muscle

Dr Henry Knipe ◉ ◈ and Dr Craig Hacking ◉ ◈ et al.

The accessory semimembranosus muscle is a rare accessory muscle of the posterior compartment of the thigh. It arises from the distal aspect of the semimembranosus muscle belly and courses through the popliteal fossa between it and the semitendinosus muscle medially and the biceps femoris laterally. It does not have an osseous insertion, instead attaching to the proximal medial head of the gastrocnemius muscle ¹.

Differential diagnosis

This muscle can be difficult to differentiate from the tensor fasciae suralis ².

References

Anatomy: Lower limb

skeleton of the lower limb
joints
- hip joint
  - ligaments
  - additional structures
  - ossification centers
- knee joint
- tibiofibular joints
  - proximal tibiofibular joint
  - distal tibiofibular syndesmosis
- ankle joint
  - regional anatomy
    - medial ankle
    - lateral ankle
    - anterior ankle
  - ligaments
    - medial collateral (deltoid) ligament
    - lateral collateral ligament
    - additional structures
    - ankle bursae
      - retrocalcaneal bursa
      - subcutaneous calcaneal bursa
    - ossification centers of the ankle
  - variants
    - ball and socket ankle joint
- foot joints
  - subtalar joint
    - articulations
      - talocalcaneal joint
      - talonavicular joint
    - ligaments
    - associated structures
  - mid-tarsal (Chopart) joint
    - calcaneonavicular joint
    - calcaneocuboid joint
  - tarsometatarsal (Lisfranc) joint
    - ligaments
      - Lisfranc ligament
  - intermetatarsal joint
  - metatarsophalangeal joint
  - interphalangeal joint
spaces of the lower limb
- adductor canal
- femoral sheath
  - femoral canal
    - femoral ring
- femoral triangle (contents mnemonic | boundaries mnemonic)
- foot subdivisions
- popliteal fossa (mnemonic)
- tarsal tunnel (mnemonic)
- triangular space of cruciate ligaments
muscles of the lower limb
- muscles of the pelvic group
  - inner hip group
    - iliopsoas muscle
  - gluteal region
    - gluteal muscles
    - tensor fasciae latae muscle
  - lateral rotator group
- muscles of the thigh
- muscles of the leg
  - anterior compartment of the leg
  - posterior compartments of the leg
    - superficial posterior compartment of the leg (calf)
      - triceps surae
        
        medial and lateral heads of the gastrocnemius muscle
        
        soleus muscle
        accessory soleus muscle
      - plantaris muscle
      - calcaneal tendon
    - deep posterior compartment of the leg
  - lateral compartment of the leg
    - peroneus brevis muscle
    - peroneus longus muscle
- muscles of the foot
  - dorsal muscles
    - extensor hallucis brevis muscle
    - extensor digitorum brevis muscle
  - plantar muscles
    - 1st layer
    - 2nd layer
      - quadratus plantae muscle
      - lumbrical muscles
    - 3rd layer
    - 4th layer
      - dorsal interossei muscles
      - plantar interossei muscles
- accessory muscles
  - accessory peroneal muscles
vascular supply
- arterial supply of the lower limb
- venous drainage of the lower limb
  - deep system
    - common femoral vein
      - femoral vein
        
        deep femoral vein
        
        popliteal vein
        
        peroneal vein
        
        posterior tibial vein
        
        anterior tibial vein
  - superficial system
    - great saphenous vein
      - dorsal venous plexus
    - small saphenous vein
      - vein of Giacomini
innervation of the lower limb
- lumbar plexus (mnemonic)
  - femoral nerve
    - saphenous nerve
  - obturator nerve
- sacral plexus
  - sciatic nerve (motor distribution)
    - common peroneal nerve
      - superficial peroneal nerve
      - deep peroneal nerve
    - tibial nerve
lymphatics

Article information

rID: 59070

System: Musculoskeletal

Section: Anatomy

Tag: variant, cases, refs

Synonyms or Alternate Spellings:

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