What are the primary muscles involved in hip flexion and how are hip flexor strains treated?

Primary Hip Flexor Muscles and Treatment of Hip Flexor Strains

The primary hip flexor muscles include the iliopsoas (composed of iliacus and psoas major), rectus femoris, sartorius, and tensor fasciae latae, with the iliopsoas functioning as the most powerful hip flexor; treatment of hip flexor strains should focus on relative rest, progressive strengthening, and gradual return to activity.

Primary Hip Flexor Muscles

The hip flexor muscle group consists of several muscles that work together to flex the hip joint:

1. Iliopsoas complex - The primary and most powerful hip flexor 1

   • Iliacus - Originates from the iliac fossa
   • Psoas major - Originates from the lumbar vertebrae
   • Psoas minor (when present) - A smaller accessory muscle

2. Secondary hip flexors

   • Rectus femoris - Part of the quadriceps group that crosses both hip and knee joints
   • Sartorius - The longest muscle in the body, assists with hip flexion
   • Tensor fasciae latae (TFL) - Also contributes to hip abduction and internal rotation

3. Accessory hip flexors

   • Adductor longus and brevis - Assist with hip flexion while primarily serving as adductors
   • Pectineus - A small muscle that assists with hip flexion and adduction

Hip Flexor Strain Treatment Algorithm

1. Acute Phase (1-7 days)

• PRICE protocol

  • Protection: Avoid activities that cause pain
  • Rest: Relative rest with modified activities
  • Ice: 15-20 minutes every 2-3 hours
  • Compression: Elastic wrap or compression shorts
  • Elevation: When possible to reduce swelling

• Pain management

  • NSAIDs if not contraindicated
  • Avoid stretching in acute phase as it may exacerbate injury 2

2. Sub-acute Phase (1-3 weeks)

• Gentle active range of motion exercises

  • Supine marching
  • Prone hip internal/external rotation

• Progressive isometric strengthening

  • Begin with isometric hip flexion exercises
  • Progress to elastic band resistance exercises 3

• Manual therapy techniques

  • Soft tissue mobilization
  • Joint mobilization if indicated

3. Rehabilitation Phase (2-6 weeks)

• Progressive strengthening program

  • Research shows significant strength improvements (17% increase) with just 6 weeks of targeted hip flexor training using elastic bands 3
  • Progress from 15 repetition maximum to 8 repetition maximum over 6 weeks

• Functional exercises

  • Single-leg balance activities
  • Step-ups and lunges
  • Core stabilization exercises

4. Return to Activity Phase (4-8 weeks)

• Sport-specific training

  • Gradual reintroduction of running, cutting, and jumping
  • Sport-specific movement patterns

• Criteria for return to full activity

  • Pain-free full range of motion
  • Strength within 90% of unaffected side
  • Successful completion of sport-specific functional tests

Clinical Considerations and Pitfalls

Biomechanical Factors

• Hip joint position significantly affects forces during strengthening exercises
• For prone hip extension exercises, highest forces occur with the hip in extension 4
• For supine hip flexion exercises, highest forces occur with the hip in extension 4

Common Pitfalls

1. Misdiagnosis - Hip flexor pain can be confused with other conditions:

   • Acetabular labral tears
   • Femoroacetabular impingement
   • Sports hernia/athletic pubalgia

2. Inadequate rehabilitation - Patients with hip labral pathology show decreased hip flexor strength compared to healthy controls, highlighting the importance of proper strengthening 5

3. Premature return to activity - Hip flexor injuries account for 5-28% of injuries in high-risk sports and require adequate rehabilitation time 2

4. Positioning concerns - When positioning patients for procedures:

   • Avoid extension of the hip beyond normal range in anesthetized patients 6
   • Limit hip flexion to 90° when possible to reduce risk of femoral neuropathy 6
   • Avoid positions that stretch the hamstring muscle group beyond comfortable range 6

Special Populations

• Athletes may require more intensive rehabilitation protocols
• Early diagnosis with MRI is increasingly important to minimize time loss from sport 2

By following this structured approach to hip flexor strain treatment with progressive loading and functional rehabilitation, most patients can achieve full recovery and return to their previous level of activity.