The anterior cruciate ligament, the ACL, is the central stabilizer of the knee, resisting forward translation of the tibia on the femur. ACL tears most commonly occur during non-contact pivoting injuries in sport: landing from a jump, cutting laterally, or planting and twisting.
ACL reconstruction is one of the most studied operations in orthopedic surgery. The principles are well-established; the art is in the details, graft choice, tunnel position, fixation, and rehabilitation timing, all matched to the demands of the individual patient.
How ACL injuries happen
Most ACL tears are non-contact injuries, the athlete plants the foot and the knee gives out, often with an audible pop. Swelling develops within hours. The classic mechanism is deceleration with the knee close to extension and the foot fixed on the ground, with internal rotation of the tibia.
Roughly half of ACL tears are accompanied by other injuries, meniscus tears, MCL injuries, or chondral damage, which can significantly sway the ultimate results. The full picture is determined by MRI and the operative arthroscopy.
How ACL tears are diagnosed
The clinical exam, Lachman test, anterior drawer, pivot shift, is highly suggestive. MRI confirms the diagnosis and identifies associated injuries. Most ACL tears are diagnosable on exam alone in experienced hands, with imaging used to plan surgery and identify concurrent damage.
The question of whether to reconstruct an ACL is partly about activity level and partly about associated injury. Older, sedentary patients with isolated tears can sometimes function well without surgery. Active patients, athletes, and patients with associated meniscus injuries generally do better with reconstruction.
Dr. Lee discusses graft options, patellar tendon (BTB), quadriceps tendon, hamstring, or allograft, based on age, sport, activity level, and personal preference. In selected patients, internal brace augmentation can shorten the recovery timeline. The rehabilitation protocol is structured around the patient's goal sport.
Non-surgical treatment
Reasonable for sedentary or low-demand patients with isolated ACL tears, particularly older patients. Structured physical therapy can restore enough functional stability for many daily activities. Patients who choose this path should understand that they are at higher risk for meniscus injury and progressive cartilage damage if they later return to pivoting sport.
ACL reconstruction
Reconstruction is performed arthroscopically. A tendon graft, typically patellar tendon (BTB), quadriceps tendon, or hamstring autograft, or in selected patients an allograft, is routed through bone tunnels in the femur and tibia and secured with interference screws or cortical button constructs.
Associated meniscus tears are repaired or trimmed at the same time. Cartilage injuries are addressed as needed. Dr. Lee uses the most modern fixation hardware throughout, and has been performing ACL reconstructions for over 25 years.
Recovery timeline
ACL reconstruction recovery follows a sport-specific timeline:
- Weeks 0–2Crutches, brace, ice, elevation. Focus on regaining full extension, controlling swelling, and beginning quadriceps activation. Most patients are off prescription pain medication within a few days.
- Weeks 2–6Progressive weight-bearing. Discontinue crutches. Begin formal physical therapy. Goals: full range of motion, normal gait, beginning strength work.
- Months 2–6Strength training. Begin straight-line running around month 3–4 in many protocols. Sport-specific drills, cutting, and pivoting added in stages.
- Months 6–12Return to sport criteria typically met around 6 months. Functional testing, single-leg hop tests, strength symmetry, psychological readiness, guide return-to-sport decisions. Returning too early is the single most preventable cause of re-injury.
What patients commonly misunderstand
What patients (and parents) often misunderstand:
- Return to sport at 6 months can be too early. Not only does it take time for the graft to incorporate and mature, certain milestones in range of motion, strength and functional testing must be met to meet the demands of the sport. Returning earlier is associated with higher re-tear rates.
- Not every ACL tear needs surgery. Older or sedentary patients with isolated tears can sometimes function well non-operatively. The decision is about activity demands and associated injuries, not about the MRI alone.
- Graft choice is not one-size-fits-all. BTB, quadriceps, hamstring, and allograft each have trade-offs. The right choice depends on age, sport, harvest site preference, and prior surgery. Dr. Lee discusses each option honestly.
This page is general educational content authored by Dr. Lee. It is not a substitute for individual medical advice. Every patient's case is different, book a consultation to discuss yours.