What causes swelling and protrusion on the anterior horn area of a meniscus repair, exacerbated by leg press and squatting, in a 12-week post-surgery patient with a history of bucket handle tear treated with all-inside technique on the posterior horn and inside-out technique on the anterior horn, who has undergone proper physical therapy and rehabilitation?

Localized Swelling and Protrusion at Anterior Horn Meniscus Repair Site

Most Likely Cause

The localized swelling and protrusion at the anterior horn repair site, exacerbated by leg press and squatting at 12 weeks post-surgery, most likely represents incomplete healing with persistent mechanical instability of the repair, potentially complicated by a parameniscal cyst formation or partial repair failure. 1, 2

Differential Diagnosis and Mechanisms

Primary Concern: Repair Instability or Partial Failure

• The inside-out technique used on the anterior horn may be experiencing mechanical stress concentration during loaded knee flexion activities like leg press and squatting, which generate significant compressive and shear forces on the anterior horn 3
• Partial repair failures can occur as "postage-stamp" effect lesions, where the suture hook or non-absorbable sutures create new smaller tears anterior to the original repair site, manifesting as localized swelling 2
• At 12 weeks, the meniscal repair is still in active healing phases and vulnerable to excessive loading, particularly with exercises that combine compression and rotation 3, 4

Parameniscal Cyst Formation

• Fluid extrusion through incompletely healed meniscal tissue can create parameniscal cysts that present as localized swelling and protrusion, particularly when intra-articular pressure increases during loaded activities 5
• These cysts are more common when meniscal tears have not achieved complete healing and allow synovial fluid to track into perimeniscal tissues 5

Technique-Specific Considerations

• The inside-out technique on the anterior horn requires suture passage through more vascular tissue but creates potential for suture knot prominence or tissue reaction that manifests as localized swelling 2
• The combination of all-inside (posterior horn) and inside-out (anterior horn) techniques may create differential healing rates, with the anterior horn potentially lagging behind 2, 6

Critical Assessment Steps

Immediate Evaluation Required

• Rule out infection first: Assess for fever, erythema, warmth, purulent drainage, or systemic inflammatory response, though infection at 12 weeks with proper rehabilitation is less likely 7, 1
• Evaluate repair integrity: Perform McMurray test and joint line palpation specifically at the anterior horn to assess for mechanical symptoms suggesting repair displacement 4
• Assess for effusion: Measure knee circumference and perform ballottement test to quantify reactive effusion, as persistent effusion indicates excessive loading 1, 8

Advanced Imaging Indications

• MRI is indicated to evaluate meniscal healing status, identify partial repair failure, detect parameniscal cyst formation, and assess for cartilage damage from altered biomechanics 4, 6
• MRI at this timepoint can differentiate between normal healing signal, incomplete healing, and frank repair failure 4, 6

Management Algorithm

Immediate Activity Modification (Critical)

• Stop leg press and squatting exercises immediately - these activities generate excessive compressive and shear forces that are disrupting the healing repair 1, 3
• The British Journal of Sports Medicine emphasizes that knee effusion or increased pain/swelling after exercise indicates excessive loading and requires immediate modification 1
• This is the most critical intervention - continuing these exercises will perpetuate the problem and potentially cause complete repair failure 1

Conservative Management Protocol

• Apply compressive cryotherapy after all activities to reduce swelling, which is more effective than cryotherapy alone 1
• Elevate the limb above heart level when resting to facilitate fluid drainage 1
• Modify rehabilitation to focus on non-weight-bearing or minimal-load exercises until swelling resolves 1, 8

Rehabilitation Adjustment

• Regress to earlier phase exercises: Return to isometric quadriceps exercises and gentle range of motion without resistance 1, 8
• Progress only when no effusion develops: The knee must demonstrate no reactive swelling before advancing exercise intensity 1, 8
• Avoid closed-chain exercises with deep knee flexion (>60 degrees) until healing is confirmed, as these create maximum meniscal compression 3
• Continue rehabilitation for the full 9-12 months as recommended, recognizing that meniscal repairs require longer healing than isolated ACL reconstruction 1

Risk Factors for Poor Healing

Patient-Specific Factors to Address

• High BMI significantly impairs meniscal healing - if BMI is elevated, weight optimization should be prioritized 6
• Smoking has a statistically significant negative effect on meniscal repair healing and must be addressed 6
• Chronic tears (>6 weeks old) may have reduced healing potential compared to acute tears, though this should not change management at this stage 6

Surgical Considerations

Indications for Revision Surgery

• If MRI demonstrates complete repair failure with displaced bucket handle fragment, revision surgery is indicated 4
• Persistent mechanical symptoms (locking, catching) despite 4-6 weeks of modified activity suggest repair failure requiring arthroscopic evaluation 2, 4
• Progressive symptoms or inability to control swelling with conservative measures warrant surgical reassessment 2

Expected Outcomes with Appropriate Management

• All-inside bucket handle repairs show 72-78% success rates when properly managed, with most failures becoming apparent by 18-24 months 4, 6
• Partial failures at the anterior horn may still achieve functional stability with activity modification and extended healing time 2

Common Pitfalls to Avoid

• Do not continue provocative exercises hoping the knee will "adapt" - this is the primary cause of repair failure 1
• Do not assume normal healing just because proper physical therapy was followed - individual healing varies and requires objective assessment 1
• Do not delay imaging if symptoms persist beyond 2-4 weeks of modified activity - early identification of repair failure allows for timely intervention 4
• Do not ignore localized swelling as "normal post-surgical response" at 12 weeks - this timepoint should show resolution of reactive symptoms with appropriate loading 1, 3