What is the treatment for a 47-year-old with severe mucoid degeneration of the Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL), posterior horn tear of the meniscus, and anterior horn tear with a parameniscal cyst?

Treatment for Severe Mucoid Degeneration of ACL/PCL with Meniscal Tears and Parameniscal Cyst

This 47-year-old patient requires arthroscopic surgery consisting of ACL/PCL debulking via radiofrequency ablation, partial meniscectomy of both torn horns, and cyst decompression, followed by structured rehabilitation—conservative management is inadequate given the multiple pathologies and mechanical symptoms. 1, 2

Surgical Approach

ACL/PCL Mucoid Degeneration Management

Arthroscopic debulking is the definitive treatment for symptomatic mucoid degeneration, which typically presents with posterior knee pain and flexion limitation. 1 The procedure involves:

• Radiofrequency ablation to systematically debulk the mucoid material while preserving ACL/PCL structural integrity 3
• Partial resection is preferred over complete resection to minimize postoperative laxity 1
• Complete ACL resection results in differential laxity averaging 8.3 mm and soft/delayed Lachman stops in 97% of cases 1

Critical caveat: At age 47, this patient is at lower risk for requiring secondary ligamentoplasty (only 2 of 27 patients in one series required this) compared to younger, more active patients. 1 However, warn the patient about potential postoperative laxity, though frank instability is rare. 1

Meniscal Tear and Cyst Treatment

Arthroscopic partial meniscectomy with cyst decompression is the standard approach for meniscal tears with associated parameniscal cysts. 2, 4

The surgical sequence includes:

• Identify the horizontal cleavage tear (present in all meniscal cyst cases) 2
• Perform partial meniscectomy of both the posterior and anterior horn tears 2
• Locate the cyst opening and perform intra-articular decompression 2
• For posterior horn involvement, use a posterior trans-septal approach for optimal cyst access 4

This approach has zero recurrence rates in published series with follow-up ranging 6-60 months, and all patients returned to previous activity levels. 2, 4

Timing Considerations

Surgery should be performed as soon as feasible given the multiple pathologies. 5 While the AAOS recommends ACL reconstruction within 3 months to protect cartilage and menisci, 5 this patient's degenerative process (mucoid degeneration at age 47) suggests a more chronic timeline is acceptable. However, the mechanical symptoms from meniscal tears and cyst warrant prompt intervention. 6

Expected Outcomes

Mucoid Degeneration Results

• Posterior pain resolution: 93% of patients within 3.7 weeks 1
• Flexion improvement: Average 21.5° gain (range 0-60°) 1
• Functional scores: Average IKDC 71.2 and KOOS 78.2 1
• Laxity trade-off: Expect increased laxity but rarely frank instability 1

Meniscal Cyst Results

• Zero recurrence with proper technique 2, 4
• Full return to activity in all reported cases 2, 4

Postoperative Rehabilitation Protocol

Early mobilization is mandatory to prevent muscular atrophy and optimize outcomes. 6

Immediate Phase (0-2 weeks)

• Weight-bearing: Expect inability to fully weight-bear for 2-7 days 6
• Pain management: NSAIDs and cryotherapy (ice through wet towel for 10-minute periods) 6
• Avoid complete immobilization 6

Early Phase (2-6 weeks)

• Structured physical therapy focusing on quadriceps and hamstring strengthening 6
• Return to sedentary work: 1-2 weeks 6
• Expected recovery completion: 2-6 weeks for most patients 6

Return to Activity

• Physical labor: Minimum 6 weeks 6
• Functional testing: Consider hop testing as one factor for return to higher-level activities 5

Important Pitfalls to Avoid

Do not perform complete ACL/PCL resection unless absolutely necessary—partial debulking maintains better stability while resolving symptoms. 1, 3 The goal is to "debulk" and lessen impingement while maintaining knee stability. 3

Do not treat the cyst without addressing the meniscal tear—the horizontal cleavage tear creates a one-way valve allowing synovial fluid extrusion, and failure to address this results in recurrence. 2, 4

Do not delay surgery in the presence of true mechanical locking—while degenerative meniscal tears in osteoarthritis generally do not benefit from arthroscopy, 6 this patient's parameniscal cyst and multiple pathologies create mechanical symptoms requiring surgical intervention.