What is the recommended treatment for a strained (sprained) anterior cruciate ligament (ACL)?

Treatment for Strained ACL

For ACL sprains/strains, treatment depends critically on whether the ligament is completely torn or partially intact, and on the patient's activity level—younger, active patients with complete tears should pursue early ACL reconstruction within 3 months to prevent secondary meniscal and cartilage damage, while partial tears or low-demand patients may succeed with structured rehabilitation alone. 1, 2

Initial Assessment and Classification

Determine if the ACL is completely torn, partially torn, or just strained:

• Complete tears are diagnosed by positive Lachman test, pivot shift test, and MRI confirmation 3
• Partial tears (10-27% of ACL injuries) require arthroscopic visualization for definitive diagnosis, as clinical exam and imaging may be unreliable 4
• Grade I-II sprains (strain without complete rupture) present with pain and swelling but maintain ligament continuity 3

Assess for concomitant injuries:

• Meniscal tears, MCL injury, or cartilage damage significantly influence treatment decisions 1
• Combined ACL/MCL tears: reconstruct the ACL but treat the MCL non-surgically in most cases 1

Treatment Algorithm Based on Injury Severity and Patient Factors

For Complete ACL Tears

Young, active patients (especially athletes in pivoting sports):

• Pursue early ACL reconstruction within 3 months of injury to reduce risk of additional cartilage and meniscal damage 2
• Graft selection hierarchy:
  • First choice: Bone-patellar tendon-bone (BPTB) autograft for young, high-demand athletes where maximum stability and lowest graft failure risk are critical 5
  • Second choice: Hamstring autograft when avoiding anterior knee pain is critical, with consideration of lateral extra-articular augmentation to reduce re-rupture risk 5, 2
• ACL reconstruction reduces risk of future meniscus pathology and may improve long-term pain and function 1

Older or less active patients:

• May consider initial trial of non-operative management with structured rehabilitation 6, 7
• If functional instability develops (repeated giving way), proceed to reconstruction 3

For Partial ACL Tears

Classify as "functional" vs "nonfunctional" based on clinical examination:

• Nonfunctional partial tears (positive pivot shift, functional instability): treat with traditional ACL reconstruction 4
• Functional partial tears in low-demand patients: attempt structured rehabilitation first 4
• Younger, active patients with partial tears have higher risk of progression to complete rupture with conservative treatment alone 4

For Grade I-II Sprains (Intact ACL)

Non-operative rehabilitation is the primary treatment:

• Structured physical therapy focusing on quadriceps and hamstring strengthening 3
• Functional bracing during rehabilitation phase (though prophylactic bracing long-term is not recommended) 1
• Activity modification to avoid pivoting and cutting until strength and stability restored 6

Non-Operative Rehabilitation Protocol (When Appropriate)

Patient must meet ALL criteria to be considered a "rehabilitation candidate": 8

• No concomitant ligament or meniscal damage 8
• Unilateral ACL injury 8
• Timed hop test score ≥80% of uninjured limb 8
• Knee Outcome Survey Activities of Daily Living Scale score ≥80% 8
• Global rating of knee function ≥60% 8
• No more than 1 episode of giving way since injury 8

Rehabilitation components: 8

• Lower extremity muscle strength training (quadriceps and hamstrings) 8
• Cardiovascular endurance training 8
• Agility and sport-specific skill training 8
• Balance perturbation training 8

Post-Reconstruction Rehabilitation Milestones

Early phase (first 6 weeks): 1

• Full extension range of motion 1
• No effusion or trace effusion only 1
• Limb symmetry index (LSI) >80% for quadriceps strength 1

Return to sport criteria (minimum requirements): 1

• No pain or swelling 1
• Full knee range of motion 1
• Stable knee on examination (negative pivot shift and Lachman) 1
• Isokinetic quadriceps and hamstring peak torque at 60°/s should display 100% symmetry for return to high-demand pivoting sports 1
• Countermovement jump and drop jump >90% symmetry 1
• Running mechanics with >90% symmetry of vertical ground reaction forces 1
• Functional hop testing should be considered as one factor in return to sport clearance 1, 2

Critical Pitfalls to Avoid

Do not delay reconstruction beyond 3 months in young, active patients as this increases risk of secondary meniscal and cartilage injury 5, 2

Do not use functional knee braces routinely after isolated primary ACL reconstruction as they confer no clinical benefit 1, 5

Do not rely solely on time-based return to sport criteria—use criterion-based functional testing instead 2

Aspiration may be considered for painful, tense effusions after acute knee injury 1