Cam Morphology in the Hip: Understanding, Symptoms, Diagnosis, and Treatment

What is Cam in Hip?

Cam morphology in the hip refers to an abnormal bony prominence on the femoral head-neck junction, which can lead to femoroacetabular impingement (FAI) by abnormally contacting the acetabulum, the hip socket, during hip movement.

Understanding Cam Morphology in the Hip

Cam morphology describes a specific anatomical variation of the femur, the thigh bone, at its connection to the hip joint. Specifically, it involves an abnormal bony overgrowth or bump on the anterior (front) or anterosuperior (front-top) aspect of the femoral head-neck junction. This bump gives the normally spherical femoral head a non-spherical, "pistol grip" deformity.

It's important to distinguish cam morphology from pincer morphology, which involves an overgrowth of the acetabulum (hip socket), and mixed impingement, which combines both cam and pincer features. While cam morphology can exist without causing symptoms, it is a significant contributor to femoroacetabular impingement (FAI), a condition where the abnormal bone shapes cause the hip bones to collide or "impinge" during movement.

Anatomy of the Hip Joint: A Brief Overview

The hip is a ball-and-socket joint, designed for extensive range of motion and weight-bearing.

• Femoral Head: The "ball" at the top of the femur, which is normally spherical.
• Acetabulum: The "socket" in the pelvis that articulates with the femoral head.
• Articular Cartilage: Smooth, slippery tissue covering the surfaces of the femoral head and acetabulum, allowing for frictionless movement.
• Labrum: A ring of fibrocartilage that lines the rim of the acetabulum, deepening the socket and providing a suction seal for joint stability.

In a healthy hip, the femoral head glides smoothly within the acetabulum across its full range of motion.

The Mechanics of Cam Impingement

When a cam deformity is present, the abnormal bony prominence on the femoral neck collides with the rim of the acetabulum during certain hip movements, particularly those involving hip flexion (bending the hip), adduction (bringing the leg towards the midline), and internal rotation. This combination of movements is common in activities like squatting, sitting, or pivoting during sports.

This repeated abnormal contact can lead to:

• Damage to the articular cartilage: The cam lesion repeatedly grinds against the cartilage, causing it to delaminate or wear away.
• Labral tears: The labrum can be pinched and torn between the cam lesion and the acetabular rim.
• Subchondral bone injury: Damage to the bone beneath the cartilage.
• Early onset osteoarthritis: Chronic impingement and damage to the cartilage and labrum can accelerate degenerative changes in the joint.

Common Symptoms Associated with Cam-Type FAI

Symptoms often develop gradually and may worsen with specific activities.

• Groin Pain: This is the most common symptom, often described as a deep, aching pain.
• Pain with Specific Movements:
  • Prolonged sitting, especially in low chairs.
  • Squatting or deep knee bends.
  • Pivoting or twisting movements.
  • Sports activities involving quick changes in direction (e.g., soccer, hockey).
  • Getting in and out of a car.
• Reduced Range of Motion: Difficulty with hip flexion, adduction, or internal rotation.
• Mechanical Symptoms: Clicking, locking, catching sensations within the hip joint.
• Referred Pain: Sometimes pain can be felt in the buttock, outer hip (trochanteric region), or even down the thigh.
• Stiffness: A feeling of tightness or restricted movement in the hip.

Diagnosing Cam-Type FAI

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

• Clinical Examination: A healthcare professional will assess your hip's range of motion, muscle strength, and perform specific tests that provoke impingement symptoms, such as the FADIR test (Flexion, Adduction, Internal Rotation).
• X-rays: Standard hip X-rays (including AP pelvis and specific views like the Dunn view) are crucial for visualizing the bony anatomy and identifying cam lesions. The alpha angle is a key measurement taken from X-rays to quantify the severity of the cam deformity.
• Magnetic Resonance Imaging (MRI): An MRI can provide detailed images of the soft tissues, including the labrum, articular cartilage, and surrounding muscles, helping to identify labral tears or cartilage damage. An MRI arthrogram (with contrast injected into the joint) can further enhance visualization.
• Computed Tomography (CT) Scan: A CT scan can provide a more precise 3D assessment of the bone morphology, which can be particularly useful for surgical planning.

Conservative Management Strategies

Initial management for symptomatic cam-type FAI is often conservative, aiming to reduce pain and improve function without surgery.

• Activity Modification: Avoiding or modifying activities that provoke pain and impingement. This might involve adjusting squat depth, avoiding deep lunges, or limiting certain sports movements.
• Physical Therapy: A structured physical therapy program is vital. It focuses on:
  • Improving Hip and Core Strength: Strengthening muscles around the hip and core to improve joint stability and control.
  • Addressing Muscle Imbalances: Correcting tightness or weakness in specific muscle groups (e.g., hip flexors, glutes).
  • Optimizing Movement Patterns: Teaching safer movement mechanics to avoid impingement.
  • Pain Management: Using modalities like ice, heat, or manual therapy.
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): Over-the-counter or prescription NSAIDs can help manage pain and inflammation.
• Corticosteroid Injections: An injection of corticosteroid into the hip joint can provide temporary pain relief and help confirm the hip as the source of pain.

Surgical Intervention: Hip Arthroscopy

If conservative measures fail to provide sufficient relief, or if there is significant structural damage (e.g., large labral tear, advanced cartilage damage), surgical intervention may be considered.

• Hip Arthroscopy: This is a minimally invasive procedure performed using small incisions and a camera (arthroscope). During the surgery, the surgeon can:
  • Reshape the Femoral Head-Neck Junction (Osteochondroplasty): The abnormal cam bump is carefully shaved down to restore a more spherical shape, allowing for smoother movement and preventing further impingement.
  • Repair or Debride Labral Tears: Torn portions of the labrum can be repaired or, if severely damaged, debrided (removed).
  • Address Cartilage Damage: Areas of damaged articular cartilage may be treated.

The goal of surgery is to restore normal hip mechanics, reduce pain, and potentially prevent or delay the onset of osteoarthritis. Post-surgical rehabilitation is crucial for a successful outcome.

Implications for Exercise and Movement

For individuals with cam morphology, whether symptomatic or not, understanding its implications for exercise is key:

• Awareness of Range of Motion: Recognize the hip's limitations, especially in deep flexion, adduction, and internal rotation.
• Prioritize Proper Form: Emphasize excellent technique in all exercises, especially squats, lunges, and deadlifts, to avoid compensatory movements or undue stress on the hip.
• Modify Exercises: Adjust exercise depth and range as needed. For example, use box squats to control depth, or widen your stance during squats to reduce impingement.
• Focus on Hip Stability and Strength: Strengthen the glutes, core, and hip rotators to improve joint control.
• Listen to Your Body: Pain is a signal. Do not push through hip pain, as this can exacerbate impingement and damage.

Conclusion and When to Seek Medical Attention

Cam morphology is a common anatomical variation that, when symptomatic, can lead to significant hip pain and dysfunction due to femoroacetabular impingement. Early diagnosis is crucial, as chronic impingement can lead to irreversible joint damage. If you experience persistent hip pain, especially with activities involving deep hip flexion or rotation, consult with a healthcare professional, such as a sports medicine physician, orthopedic surgeon, or physical therapist. They can accurately diagnose the condition and guide you toward the most appropriate management plan to preserve hip health and function.