Ankylosis: Definition, Types, Causes, and Management

What Does Ankylosis Mean?

Ankylosis refers to the abnormal stiffness and immobility of a joint, caused by fusion of the bones within the joint, either naturally or as a result of disease, injury, or surgical intervention. This fusion can significantly limit or completely eliminate a joint's range of motion, leading to functional impairment.

Definition of Ankylosis

Ankylosis, derived from the Greek word "ankylos" meaning "bent" or "crooked," describes a pathological condition where a joint becomes stiff and loses its normal range of motion due to the formation of a bony or fibrous union across the joint space. Essentially, the joint, which is designed for movement, becomes rigid and fixed. This fusion can occur within the joint capsule (intra-articular) or outside of it (extra-articular), leading to varying degrees of immobility.

Types of Ankylosis

Understanding the different types of ankylosis is crucial for appreciating its diverse manifestations and implications.

• True Ankylosis (Bony Ankylosis): This is the most severe form, characterized by the complete fusion of bones across a joint, resulting in a solid, continuous bone structure where the joint once was. This complete osseous fusion eliminates all movement at the affected joint. It often occurs as the end-stage of chronic inflammatory conditions or severe trauma.
• Fibrous Ankylosis: In this type, the joint space is obliterated not by bone, but by dense fibrous tissue. While it causes significant restriction of movement, some minimal motion might still be possible, often accompanied by pain. This can be an intermediate stage before bony ankylosis or a stable, less severe form of fusion.
• False Ankylosis (Pseudoankylosis or Extra-articular Ankylosis): This term is used when the immobility of a joint is not due to a problem within the joint itself, but rather to external factors. These factors can include contractures of muscles, ligaments, or tendons surrounding the joint, scarring of soft tissues, or bony bridges forming outside the joint capsule. While the joint surfaces themselves remain intact, external compression or restriction prevents normal movement.

Causes of Ankylosis

Ankylosis can arise from a variety of underlying conditions and events:

• Inflammatory Arthritis: Chronic inflammatory conditions are a primary cause.
  • Ankylosing Spondylitis (AS): A classic example, AS primarily affects the spine, leading to inflammation that can cause vertebrae to fuse, resulting in a rigid "bamboo spine." It can also affect peripheral joints.
  • Rheumatoid Arthritis (RA): Severe, long-standing RA can lead to joint destruction and subsequent fibrous or bony ankylosis, particularly in the hands and feet.
  • Psoriatic Arthritis, Reactive Arthritis, Enteropathic Arthritis: Other forms of spondyloarthritis can also lead to joint fusion.
• Trauma or Injury: Severe fractures extending into a joint, dislocations, or repetitive microtrauma can damage articular cartilage and subchondral bone, initiating a process of repair that may result in fusion. Prolonged immobilization after injury can also contribute to stiffness.
• Infection: Septic arthritis (joint infection) can cause rapid and severe destruction of joint cartilage, leading to ankylosis if not promptly treated.
• Surgery: Arthrodesis, or joint fusion surgery, is a deliberate surgical procedure performed to eliminate pain and stabilize a severely damaged or unstable joint by intentionally fusing the bones. This is a controlled form of ankylosis.
• Degenerative Joint Disease (Osteoarthritis): While less common than inflammatory conditions, severe, end-stage osteoarthritis can sometimes lead to localized bony spurs (osteophytes) or complete joint space narrowing that mimics or progresses to a form of ankylosis.
• Congenital Conditions: Rarely, individuals may be born with joints that are partially or completely fused due to developmental abnormalities.
• Heterotopic Ossification (HO): The abnormal formation of bone in soft tissues where bone normally does not exist, often following severe trauma (e.g., burns, spinal cord injury, head injury) or surgery, can cause false ankylosis by bridging across a joint.

Common Joints Affected

While any joint can potentially be affected, some are more commonly involved:

• Spine: Particularly in ankylosing spondylitis, leading to a rigid back and neck.
• Hips and Knees: Often due to severe osteoarthritis, trauma, or inflammatory arthritis.
• Shoulders and Elbows: Commonly affected by trauma, surgery, or inflammatory conditions.
• Small Joints of Hands and Feet: Frequent sites of ankylosis in rheumatoid arthritis.
• Temporomandibular Joint (TMJ): Can be affected by trauma, infection, or inflammatory conditions, leading to difficulty opening the mouth.

Symptoms and Impact on Function

The primary symptom of ankylosis is a profound loss of joint range of motion (ROM), progressing to complete immobility. Other symptoms include:

• Stiffness: Especially after periods of rest.
• Pain: While the initial inflammatory process may be painful, once full bony fusion occurs, the pain from movement typically subsides, as there is no longer movement to cause pain. However, compensatory movements in adjacent joints or muscle strain can cause secondary pain.
• Functional Limitations: The inability to move the affected joint severely impacts daily activities. For example, spinal ankylosis affects posture, balance, and the ability to look up or turn the head. Hip ankylosis impairs walking, sitting, and bending.

Diagnosis

Diagnosis typically involves:

• Physical Examination: Assessing joint range of motion, tenderness, and posture.
• Medical History: Inquiring about inflammatory conditions, past injuries, and symptoms.
• Imaging Studies:
  • X-rays: Can visualize bony fusion, joint space narrowing, and characteristic changes like syndesmophytes in AS.
  • MRI (Magnetic Resonance Imaging): Provides detailed images of soft tissues, cartilage, and bone marrow edema, useful for early detection of inflammation or fibrous ankylosis.
  • CT (Computed Tomography) Scan: Excellent for visualizing complex bony anatomy and fusion, particularly useful in the spine or difficult-to-image joints.

Management and Treatment

The approach to ankylosis depends on its cause, type, and severity.

• Physical Therapy and Rehabilitation: Crucial for maintaining existing mobility in adjacent joints, strengthening surrounding muscles to support function, improving posture, and preventing further progression where possible. For established ankylosis, the focus shifts to optimizing compensatory movements and functional independence.
• Medication: For inflammatory causes, disease-modifying anti-rheumatic drugs (DMARDs), biologics, and NSAIDs are used to control inflammation and potentially slow the progression of fusion.
• Surgical Intervention:
  • Arthroplasty (Joint Replacement): In some cases, such as severe hip or knee ankylosis, joint replacement surgery can restore mobility and function.
  • Osteotomy: A surgical procedure to cut and realign bone, which can sometimes be used to correct severe deformities caused by ankylosis, particularly in the spine.
  • Arthrodesis: As mentioned, this is a deliberate surgical fusion, typically performed for pain relief and stability in severely damaged joints.

Implications for Exercise and Rehabilitation

For fitness enthusiasts, personal trainers, and student kinesiologists, understanding ankylosis is vital because it profoundly impacts exercise prescription and rehabilitation strategies.

• Individualized Approach: Exercise programs must be highly individualized, considering the specific joints affected, the type of ankylosis, the degree of fusion, and the underlying cause. A medical clearance and consultation with a physical therapist are essential.
• Focus on Preservation and Function: When complete fusion is present, the goal shifts from restoring range of motion to preserving function in unaffected joints, strengthening musculature around the fused joint to enhance stability and compensate for immobility, and improving overall cardiovascular fitness.
• Posture and Alignment: For spinal ankylosis, exercises focusing on maintaining upright posture, core strength, and balance are critical to prevent further kyphosis and reduce the risk of falls.
• Flexibility and Mobility in Adjacent Joints: While the ankylosed joint cannot move, maintaining and improving flexibility in the joints directly above and below it is crucial to maximize overall body movement and prevent secondary issues.
• Pain Management: Exercise can play a role in managing secondary pain from muscle strain or compensatory movements, but activities that exacerbate pain in the fused joint should be avoided.
• Careful Load Management: In cases of fibrous ankylosis or early bony fusion, excessive or inappropriate loading could potentially worsen the condition or cause injury.
• Education and Awareness: Educating clients or patients about the nature of their ankylosis, realistic expectations for mobility, and the importance of consistent, appropriate exercise is paramount for long-term management and quality of life.

Ankylosis represents a significant challenge to joint mobility and function. While its causes are varied, a comprehensive understanding of its types, progression, and the principles of exercise science and rehabilitation can significantly improve the quality of life for affected individuals.