Ankle Impingement: Causes, Types, and Prevention

What causes ankle impingement?

Ankle impingement refers to a condition where soft tissues or bony structures within the ankle joint become compressed or "pinched" during specific movements, leading to pain, inflammation, and restricted range of motion.

Understanding Ankle Impingement

Ankle impingement syndrome is a common cause of chronic ankle pain, particularly among athletes. It occurs when structures within the ankle joint are mechanically compressed between the bones, most often during extreme end-range movements like dorsiflexion (toes moving towards shin) or plantarflexion (toes pointing away). This compression can involve various tissues, including the joint capsule, ligaments, scar tissue, synovial lining, or even bony growths (osteophytes).

Types of Ankle Impingement

The location of the impingement dictates its classification, with each type having specific common causes:

• Anterior Ankle Impingement: The most common type, occurring at the front of the ankle, often during forced dorsiflexion. It can be:
  • Bony Impingement: Caused by osteophytes (bone spurs) forming on the front of the tibia or talus, reducing joint space.
  • Soft Tissue Impingement: Involves pinching of inflamed synovium, scar tissue, or thickened ligaments.
• Posterior Ankle Impingement: Occurs at the back of the ankle, typically during forced plantarflexion. It can involve:
  • Bony Impingement: Often due to an os trigonum (an extra bone behind the talus) or osteophytes on the posterior talus or tibia.
  • Soft Tissue Impingement: Pinching of posterior capsule, scar tissue, or flexor hallucis longus (FHL) tendon issues.
• Anterolateral Ankle Impingement: Less common, affecting the front-outer aspect of the ankle. It is almost exclusively soft tissue related, often involving scar tissue or synovitis from previous lateral ankle sprains.

Primary Causes and Contributing Factors

Ankle impingement is rarely caused by a single event but rather a combination of factors leading to chronic irritation and structural changes.

• Repetitive Microtrauma and Overuse:
  • Activities requiring repeated or sustained end-range ankle movements, such as deep squats, running uphill, ballet pointe work, soccer kicking, or gymnastics landings, can lead to chronic irritation.
  • This constant compression causes inflammation and can stimulate the body to lay down extra tissue (scar tissue) or bone (osteophytes) in an attempt to stabilize the joint, inadvertently worsening the impingement.
• Acute Ankle Trauma:
  • Ankle Sprains: Especially recurrent inversion ankle sprains, are a leading cause of soft tissue impingement. The initial injury can lead to inflammation, hemorrhage, and subsequent scar tissue formation (fibrosis) in the joint capsule or ligaments (e.g., anterolateral gutter). This thickened scar tissue can then get pinched.
  • Fractures: Previous ankle fractures can alter joint mechanics or lead to malunion, predisposing to impingement.
• Bony Spurs (Osteophytes):
  • These abnormal bone growths develop on the edges of the bones that form the ankle joint (tibia and talus). They are often a result of chronic stress, repetitive microtrauma, or degenerative changes (osteoarthritis).
  • Osteophytes mechanically reduce the available space within the joint, causing direct impingement during movement.
• Soft Tissue Hypertrophy and Scar Tissue:
  • Chronic inflammation, often following an injury like an ankle sprain, can lead to the thickening (hypertrophy) of the joint capsule lining (synovium) or ligaments.
  • The body's healing response can also produce excessive scar tissue (fibrosis) in the impingement zone. This thickened, less pliable tissue can then be easily compressed.
• Anatomical Variations:
  • Os Trigonum: A small, accessory bone located behind the talus. In some individuals, it can become entrapped or inflamed during extreme plantarflexion, leading to posterior impingement.
  • Talar Dome Lesions: Cartilage damage on the top of the talus can alter joint mechanics and contribute to impingement symptoms.
• Biomechanical Imbalances:
  • Muscle Weakness/Imbalance: Weakness in stabilizing muscles around the ankle (e.g., peroneal muscles) can lead to poor joint control and increased stress on the joint structures.
  • Limited Dorsiflexion: Pre-existing restrictions in ankle dorsiflexion range of motion can force the joint into impingement earlier during movements.
  • Foot Type: Certain foot mechanics, such as excessive pronation or supination, can alter ankle alignment and predispose to impingement.
• Inadequate Rehabilitation:
  • Following an ankle injury, insufficient or incomplete rehabilitation can leave residual weakness, instability, or unaddressed scar tissue, increasing the likelihood of developing chronic impingement.

The Biomechanical Mechanism of Impingement

At its core, ankle impingement occurs when there is a mismatch between the available space in the joint and the volume of the structures within that space during movement.

During ankle motion, particularly at the end ranges, the bones move closer together. If there are enlarged structures (osteophytes, thickened scar tissue, inflamed synovium) or if the joint kinematics are altered (e.g., due to instability), these structures get "pinched" between the opposing bone surfaces. This mechanical compression irritates the tissues, leading to:

• Pain: Directly from the pinched tissue.
• Inflammation: The body's response to irritation and injury.
• Swelling: Accumulation of fluid in the joint.
• Further Tissue Thickening: Chronic inflammation can lead to more scar tissue formation, creating a vicious cycle that perpetuates the impingement.
• Restricted Range of Motion: The pain and mechanical block prevent full movement.

Prevention Strategies

While not all cases of ankle impingement are preventable, several strategies can reduce risk, especially for those involved in high-impact or repetitive ankle movements:

• Proper Warm-up: Prepare ankle tissues for activity.
• Gradual Progression: Avoid sudden increases in training volume or intensity.
• Strength and Stability Training: Focus on strengthening muscles surrounding the ankle (dorsiflexors, plantarflexors, invertors, evertors) and improving proprioception (balance).
• Address Ankle Instability: Thoroughly rehabilitate previous ankle sprains to restore full strength, range of motion, and proprioception.
• Appropriate Footwear: Wear shoes that provide adequate support and cushioning for your activity.
• Listen to Your Body: Do not push through persistent ankle pain; seek professional assessment if symptoms arise.

Conclusion

Ankle impingement is a complex condition stemming from a variety of factors, predominantly repetitive microtrauma, acute injuries (especially ankle sprains), and the subsequent development of bony spurs or soft tissue thickening. Understanding these underlying causes is crucial for effective prevention, diagnosis, and management, allowing individuals to maintain optimal ankle health and function.