Pseudo Joint: Definition, Causes, Symptoms, and Treatment

What is pseudo joint?

A pseudo joint, also known as a neoaarthrosis or false joint, is an abnormal articulation that forms between two bones that are not naturally designed to articulate, typically as a result of a fracture that fails to heal properly (non-union) or following a surgical procedure.

Understanding True Joints vs. Pseudo Joints

To comprehend a pseudo joint, it's essential to first understand what constitutes a true anatomical joint. A true joint is a site where two or more bones meet, designed by nature to allow movement (synovial joints) or provide stability (fibrous or cartilaginous joints). These articulations feature specific structures like articular cartilage, joint capsules, synovial fluid, and supporting ligaments, all contributing to smooth, controlled motion or robust connection.

In stark contrast, a pseudo joint is an abnormal formation. It lacks the intricate, organized anatomical structures of a true joint and arises pathologically. While it may allow some degree of movement, this movement is often unstable, painful, and dysfunctional, occurring where no natural joint should exist.

The Mechanics of a Pseudo Joint (Neoaarthrosis)

The term "neoaarthrosis" literally means "new joint," but it's crucial to understand this "new joint" is a pathological entity. Pseudo joints typically form when a bone fracture fails to unite (a condition known as non-union) or following certain surgical procedures, particularly failed arthrodesis (joint fusion). Instead of the fractured bone ends knitting together through the normal bone healing process (osteogenesis), the body attempts to adapt to the persistent motion between the fragments.

The formation process often involves:

• Fibrous Tissue Formation: Connective tissue, similar to scar tissue, forms between the bone ends.
• Cavity Formation: Over time, a fluid-filled cavity, resembling a rudimentary joint capsule, may develop within this fibrous tissue due to the constant motion and friction.
• Cartilage-like Tissue: In some cases, areas resembling fibrocartilage or hyaline cartilage might form on the opposing bone surfaces, attempting to mimic articular cartilage.
• Lack of Stability: Crucially, these structures are disorganized and lack the necessary biomechanical integrity and stability of a true joint.

Common Causes and Locations

Pseudo joints are primarily a complication of bone healing and are not naturally occurring anatomical structures.

• Fracture Non-Union: This is the most common cause. When a bone fracture fails to heal within a reasonable timeframe (typically 6-9 months, depending on the bone and severity), and there is persistent motion at the fracture site, the body may attempt to create a "false joint." Factors contributing to non-union include:
  • Inadequate immobilization of the fracture.
  • Poor blood supply to the fracture site.
  • Infection.
  • Significant soft tissue damage.
  • Interposition of soft tissue between bone fragments.
  • Systemic factors (e.g., malnutrition, certain medications, smoking).
• Post-Surgical Complications: Pseudo joints can form after failed attempts to fuse a joint (arthrodesis). If the fusion does not achieve solid bony union, motion may persist, leading to a pseudo joint.
• Congenital Pseudoarthrosis: Rarely, a child may be born with a pseudo joint, most commonly in the tibia (shin bone), where the bone fails to form properly.

Pseudo joints can occur in any bone that suffers a non-union, but they are more frequently observed in:

• Long bones like the tibia, femur, and humerus.
• The scaphoid bone in the wrist (due to its precarious blood supply).
• The clavicle (collarbone).
• The spine after failed spinal fusion surgery.

Symptoms and Clinical Presentation

The symptoms of a pseudo joint vary depending on its location, size, and the degree of instability, but commonly include:

• Persistent Pain: Often localized to the site of the pseudo joint, worsening with activity or weight-bearing.
• Instability: A feeling of "giving way" or abnormal looseness in the affected limb or segment.
• Swelling and Tenderness: Local inflammation may be present, especially after activity.
• Crepitus: A grinding, popping, or clicking sensation during movement.
• Decreased Function: Limited range of motion, weakness, or inability to bear weight due to pain and instability.
• Deformity: Visible angulation or shortening of the limb, particularly in long bone pseudo joints.

Diagnosis of a Pseudo Joint

Diagnosis typically involves a combination of clinical assessment and imaging studies.

• Clinical Examination: A thorough medical history is taken, focusing on previous injuries or surgeries. The affected area is palpated for tenderness and swelling, and the range of motion and stability are assessed.
• Imaging Studies:
  • X-rays: The primary diagnostic tool. X-rays can show the non-union of the fracture, the presence of sclerotic (dense) bone ends, and sometimes a visible gap or "joint space" between the fragments.
  • Computed Tomography (CT) Scan: Provides more detailed cross-sectional images of the bone, helping to visualize the exact morphology of the pseudo joint and the extent of bone loss or deformity.
  • Magnetic Resonance Imaging (MRI): Useful for assessing the soft tissue components, such as the fibrous tissue, fluid collection, and any associated inflammation around the pseudo joint.

Management and Treatment Approaches

The management of a pseudo joint is challenging and often requires surgical intervention due to its pathological nature and the persistent symptoms it causes.

• Non-Surgical Management: These approaches are generally aimed at symptom management and are rarely curative for the pseudo joint itself.
  • Pain Management: Non-steroidal anti-inflammatory drugs (NSAIDs), analgesics, and sometimes nerve blocks.
  • Physical Therapy: Focuses on strengthening surrounding muscles to improve stability, maintaining range of motion in adjacent true joints, and teaching compensatory strategies.
  • Bracing or Orthotics: To provide external support and limit painful movement.
  • Activity Modification: Avoiding activities that exacerbate pain or instability.
• Surgical Intervention: This is often necessary to achieve stability and alleviate symptoms.
  • Excision of Fibrous Tissue: Removing the abnormal fibrous tissue and any fluid-filled cavity.
  • Preparation of Bone Ends: Freshening the bone ends to promote new bone growth.
  • Bone Grafting: Autologous bone graft (from the patient's own body) or allograft (from a donor) is often used to provide a scaffold and osteoinductive factors to stimulate healing.
  • Internal Fixation: Using plates, screws, rods, or wires to rigidly stabilize the bone fragments, allowing them to heal.
  • External Fixation: In complex cases, an external frame may be applied to stabilize the bones and allow for limb lengthening or deformity correction.
  • Arthrodesis (Fusion): In some cases, particularly in joints where stability is prioritized over movement (e.g., spine, ankle), the pseudo joint may be surgically fused to create a solid bony union.

Implications for Movement and Exercise

For individuals with a pseudo joint, exercise and movement must be approached with extreme caution and under the guidance of healthcare professionals (orthopedic surgeons, physical therapists).

• Pain-Limited Movement: Pain is a significant barrier to effective movement and exercise. Activities must be carefully scaled to avoid aggravating the pseudo joint.
• Instability Risk: The lack of true joint stability means that high-impact activities, sudden movements, or activities that put torsional stress on the pseudo joint must be avoided.
• Compensatory Patterns: The body may develop abnormal movement patterns to avoid pain, which can lead to secondary issues in other joints or muscles.
• Rehabilitation Focus: Post-surgical rehabilitation focuses on regaining strength, restoring range of motion in adjacent healthy joints, improving proprioception, and gradually increasing functional capacity while protecting the healing site.
• Professional Guidance: Working closely with a physical therapist is crucial to ensure exercises are safe, effective, and tailored to the individual's specific condition and recovery phase.

Conclusion

A pseudo joint, or neoaarthrosis, is a pathological condition characterized by the formation of an abnormal articulation, most commonly due to a fracture non-union. Unlike true joints, pseudo joints are dysfunctional, often causing persistent pain, instability, and impaired function. While non-surgical methods can help manage symptoms, definitive treatment often requires surgical intervention to achieve bony union and restore stability. Understanding the nature of pseudo joints is vital for accurate diagnosis, appropriate management, and guiding safe and effective rehabilitation strategies in the realm of exercise science and kinesiology.