How should I work up a patient with right calf pain and intermittent right lateral thigh numbness, status post (s/p) anterior cruciate ligament (ACL) repair?

Workup for Right Calf Pain and Intermittent Right Lateral Thigh Numbness Post-ACL Repair

This presentation requires immediate evaluation for deep vein thrombosis (DVT) given the calf pain, followed by assessment for nerve injury or compression related to the prior ACL surgery, and evaluation for lumbar radiculopathy causing the lateral thigh numbness.

Immediate Priority: Rule Out DVT

• Obtain a lower extremity venous duplex ultrasound urgently to exclude DVT, as calf pain post-orthopedic surgery is a red flag for thromboembolic disease, even years after the procedure
• Assess for clinical signs: calf tenderness, warmth, swelling, Homan's sign, and measure calf circumference comparing both legs
• Calculate Wells score to stratify DVT probability and guide D-dimer testing if indicated

Neurological Assessment

Lateral Thigh Numbness (Meralgia Paresthetica vs. L2-L3 Radiculopathy)

• Examine the distribution carefully: Lateral thigh numbness suggests either meralgia paresthetica (lateral femoral cutaneous nerve compression) or L2-L3 nerve root involvement
• Test sensation over the lateral thigh in the distribution of the lateral femoral cutaneous nerve
• Assess for Tinel's sign at the inguinal ligament (just medial to the anterior superior iliac spine)
• Perform straight leg raise and femoral nerve stretch test to evaluate for lumbar radiculopathy
• Check hip flexor (L2-L3) and quadriceps (L3-L4) strength bilaterally

Evaluate for Surgical Nerve Injury

• Assess for saphenous nerve injury if hamstring autograft was used, as this nerve can be injured during graft harvest 1
• Examine for common peroneal nerve dysfunction (foot drop, lateral leg numbness) if there was prolonged tourniquet use or positioning issues during surgery
• Document any sensory deficits in dermatomal patterns

Musculoskeletal Evaluation

Knee-Specific Assessment

• Measure quadriceps and hamstring strength bilaterally using manual muscle testing or isokinetic testing, as >20% strength deficit has significant negative consequences 1
• Assess for knee effusion, warmth, or increased temperature suggesting inflammatory process 1
• Check knee range of motion (ROM) - should have full extension and at least 95% flexion compared to contralateral side 1
• Perform Lachman test and pivot shift to assess graft integrity and knee stability 1

Calf Pain Evaluation

• Palpate the gastrocnemius and soleus muscles for focal tenderness, masses, or defects
• Assess for Achilles tendinopathy or insertional pain
• Evaluate ankle dorsiflexion and plantarflexion strength
• Check for compartment syndrome signs (though unlikely years post-op): pain with passive stretch, tense compartments, paresthesias

Functional Assessment

• Perform single-leg hop test and assess for pain reproduction during functional activities 1
• Observe gait pattern for antalgic gait, Trendelenburg sign, or compensatory patterns 1
• Assess limb symmetry index (LSI) for functional activities - should be >90% for normal function 1

Imaging Studies

Initial Imaging

• Obtain knee radiographs (AP, lateral, sunrise views) to evaluate for:
  • Hardware complications (tunnel widening, screw prominence)
  • Patellofemoral arthritis
  • Tibiofemoral joint space narrowing
  • Cyclops lesion (anterior impingement)

Advanced Imaging (If Initial Workup Non-Diagnostic)

• MRI of the knee if concern for:

  • Graft failure or elongation
  • Meniscal tear (new or missed concomitant injury)
  • Cartilage injury
  • Bone marrow edema
  • Soft tissue pathology

• Lumbar spine MRI if radicular symptoms persist and suggest L2-L3 nerve root compression

• Nerve conduction studies/EMG if peripheral nerve injury suspected and symptoms persist beyond 6-8 weeks

Laboratory Studies

• Complete blood count (CBC) if infection suspected (fever, warmth, systemic symptoms)
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) if concerned about delayed infection or inflammatory arthropathy
• D-dimer if DVT probability is low-to-moderate on Wells score

Common Pitfalls to Avoid

• Do not dismiss calf pain as "muscle soreness" without excluding DVT, especially if there are any risk factors (immobility, recent travel, oral contraceptives, smoking)
• Do not assume all symptoms are related to the ACL repair - lateral thigh numbness is anatomically distant and suggests a separate pathology (lumbar spine or inguinal ligament compression)
• Do not overlook psychological factors - chronic pain and functional limitations post-ACL reconstruction can be influenced by kinesiophobia and poor self-efficacy 1
• Do not forget to assess the contralateral limb for comparison of strength, ROM, and functional performance 1

Red Flags Requiring Urgent Evaluation

• Sudden onset severe calf pain with swelling (DVT)
• Progressive neurological deficit or weakness
• Signs of infection: fever, erythema, warmth, drainage
• Acute knee instability or giving way (graft failure)
• Inability to bear weight

Rehabilitation Considerations

If the workup is negative for serious pathology, the patient may have inadequate rehabilitation completion:

• Rehabilitation should continue for 9-12 months post-ACL reconstruction depending on return-to-activity goals 1
• Patients require supervised physical therapy to address quadriceps inhibition, strength deficits, and neuromuscular control 1
• Calf pain may represent compensatory overuse from altered gait mechanics or inadequate proximal strength 1