Quadriceps Femoris Muscle

Quadriceps Femoris Muscle

This is the Quadriceps Femoris PDF for you to download

Quadriceps Femoris is the key functional muscle of the canine hindlimb (pelvic limb).

This is found on the cranial aspect of the thigh and lies between the pelvis - femur proximally - patella and tibial tuberosity distally.

The canine Quadriceps Femoris has 4 heads that cover the femur cranially, medially and laterally;

  • Vastu Lateralis; covers Rectus Femoris laterally and EMG studies show it's active in stifle extension in the stance phase. This muscle has 40% Type 1 slow twitch muscle fibres
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Clinical Tip: this is why it is crucial for therapists to include static work in natural balanced stance in their treatment plan.

  • Vastu Medialis; lies deep to and is covered by the Sartorius muscle. It's laterally compressed shape wise, and covers the distal part of Rectus Femoris medially. Just proximal to the patella, it's tendinous element fuses with Rectus Femoris. It has 40% Type I slow twitch muscle fibres like Vastu Lateralis
  • Vastu Intermedius; is the smallest component of Quadriceps Femoris and arises with Vastu Lateralis which covers it. The terminal tendinous elements fuses with Vastu Medialis. It has 88% Type I slow twitch muscle fibres
  • Rectus Femoris; spans 2 joints and lies deep to the Sartorius and Tensor Fascia Late (TFL) muscles. It has 40% Type I slow twitch fibres and shows two bursts of activity in walking. The first burst is during the swing phase, so Rectus Femoris contributes to hip flexion and hind limb protraction. The second burst is in the stance phase where it works synergistically with the other components and evidences it's importance as a key antigravity muscle

Red = Rectus Femoris / Yellow = Vastu Medialis / Green = Vastu Lateralis / Blue = Vastu Intermedius

Rectus Femoris origin identified with pointer.
Rectus Femoris origin identified with pointer.

Pointer identifying tibial tuberosity = insertion of straight patella ligament, also known as Quadriceps Femoris tendon of insertion.
Pointer identifying tibial tuberosity = insertion of straight patella ligament, also known as Quadriceps Femoris tendon of insertion.
Lateral view: origins of Vastu Intermedius (blue) and Rectus Femoris (red).
Lateral view: origins of Vastu Intermedius (blue) and Rectus Femoris (red).
Birds eye view: origin of Vastu Medialis on proximal femur (yellow).
Birds eye view: origin of Vastu Medialis on proximal femur (yellow).

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Quadriceps Femoris is an antigravity muscle and stifle extensor in the stance phase, with the Rectus Femoris also being a hip flexor due to its attachments.

Innervation of Quadriceps

Quadriceps Femoris is innervated by the femoral nerve, which is part of the lumbosacral plexus.

As a rule if a nerve passes through a muscle, it tends to innervate it.

Nerve route: The femoral nerve arises from L4 - L6 spinal nerves and enters the Quadriceps muscle between Rectus Femoris and Vastu Medialis. innervating all 4 heads of Quadriceps Femoris.

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Clinical Tips: Injuries to the femoral nerve prior to it entering the Quadriceps muscle, leads to the inability of the hind limb to support the dogs weight. Due to the muscle insertion onto the tibial tuberosity of the tibial bone, the Quadriceps Femoris is a very important stifle stabiliser. It's essential to reinstate the extensor pattern of support in these cases using a multi modal treatment approach.

Summary

  • Rectus Femoris passes over two joints, whereas the other 3 heads pass over one joint
  • Muscles have the greatest force exerted at their origin and insertion (attachments), so these are the more common sites for muscle injury
  • Understanding the arrangement of the different components of Quadriceps Femoris with its surrounding fascia will empower your assessment accuracy and efficacy of your selected treatment techniques.
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Rectus Femoris is more commonly injured than the other 3 components of this muscle.

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