Long Plantar Ligament: Attachments, Anatomy, Function, and Clinical Relevance

What is the attachment of the long plantar ligament?

The long plantar ligament is a robust ligament of the foot that originates from the plantar aspect of the calcaneus (heel bone) and extends forward to primarily insert onto the plantar surface of the cuboid bone, with more superficial fibers continuing to attach to the bases of the 2nd, 3rd, 4th, and 5th metatarsal bones.

Anatomy and Location

The long plantar ligament (also known as the long plantar calcaneocuboid ligament) is the longest and strongest ligament on the plantar (sole) aspect of the foot. It plays a pivotal role in maintaining the integrity and stability of the longitudinal arch, particularly the lateral portion. Its substantial structure allows it to withstand significant tensile forces during weight-bearing activities.

Specific Attachments

Understanding the precise attachments of the long plantar ligament is crucial for comprehending its biomechanical function:

• Proximal Attachment (Origin): The ligament originates from the plantar surface of the calcaneus (heel bone). Specifically, it arises from the rough area anterior to the calcaneal tuberosity, which is the large bony prominence at the back of the heel.
• Distal Attachments (Insertion): The ligament then courses anteriorly, dividing into two main sets of fibers:
  • Deeper, Shorter Fibers: These fibers attach directly to the plantar surface of the cuboid bone. This is considered the primary insertion point for the deeper part of the ligament. These fibers are crucial for stabilizing the calcaneocuboid joint.
  • Superficial, Longer Fibers: These fibers continue beyond the cuboid bone, extending further anteriorly to attach to the bases of the 2nd, 3rd, 4th, and 5th metatarsal bones. These more superficial fibers are instrumental in forming a fibrous tunnel or groove on the plantar surface of the cuboid, through which the tendon of the fibularis (peroneus) longus muscle passes as it crosses the foot.

Functional Significance

The distinct attachments of the long plantar ligament confer several critical biomechanical functions:

• Primary Stabilizer of the Lateral Longitudinal Arch: By spanning from the calcaneus to the cuboid and metatarsals, it acts as a strong tie-beam, preventing the collapse of the lateral longitudinal arch of the foot during weight-bearing and propulsion.
• Weight Distribution: It helps distribute forces across the midfoot and forefoot, absorbing shock and maintaining the foot's structural integrity.
• Support for Fibularis Longus Tendon: The superficial fibers create a retinaculum or sheath that guides and supports the fibularis longus tendon, optimizing its mechanical advantage as it crosses the plantar aspect of the cuboid to insert onto the first metatarsal and medial cuneiform.
• Joint Stability: It contributes significantly to the stability of the calcaneocuboid joint, which is a key articulation in the midfoot.

Clinical Relevance

Given its critical role in foot mechanics, the long plantar ligament is clinically significant:

• Plantar Fasciitis Differential: While often overlooked, injuries or inflammation of the long plantar ligament can mimic or coexist with plantar fasciitis, causing pain in the heel and midfoot.
• Arch Support Issues: Dysfunction or laxity of this ligament can contribute to the flattening of the longitudinal arch (pes planus) or chronic foot instability.
• Traumatic Injury: Direct trauma or excessive pronation/supination forces can lead to sprains or tears of the ligament, resulting in localized pain, swelling, and impaired function.
• Rehabilitation: Understanding its attachments is vital for targeted rehabilitation exercises aimed at strengthening the surrounding musculature and improving overall foot stability.