Post ACL Surgery, Will My Knee Be Like A Normal Knee

ACL (Anterior Cruciate Ligament) surgery for the knee ligament injury entails recreating the ACL by using one's own tendon tissue - autograft (often hamstring tendons). Although the surgery is performed using an arthroscope (key-hole surgery), it involves drilling tunnels in the bone to place the graft in the correct position and alignment. Secondly to fix the graft and  hold it in place either bioscrews or titanium buttons are used. It is a technically advanced procedure which aims to recreate normal anatomy. After ACL surgery, many patients regain the knee functions well, but whether it will be "like a normal knee" depends on several factors.

In spite of the attempt to recreate the normal anatomy, several challenges still remain.

• Graft Acceptance: The tendon used as a graft would be avascular and lack blood supply at least for the first few months.
• Proprioception: The natural proprioception (nerve-sense of the spatial positioning of the native ACL in the knee does not work in the same way as natural ligament proprioception would.
• Bone Ingrowth: In the bone tunnels the bone has to start ingrowing into the graft which takes time.
• Foreign Materials: Although titanium and bio-screws are bio-friendly and bone-friendly, the body may still reject these and cause inflammation around them.
• Scar Tissue: The scar tissue formation can affect the knee's range of motion and sensation.
• Muscle imbalances: Post ACL surgery muscle stiffness and weakness can be the challenges one may face in spite of diligent physiotherapy and rehabilitation.

Type of Graft: The selection of the graft matters in terms of duration of recovery, outcomes and graft donor site morbidity. To recreate ACL either hamstrings, quads tendon, patellar tendon or the peroneal tendon gets used. Each graft has its own pros and cons. Patellar tendon (BTB) provides one distinct advantage of bone to bone healing and hence can be more secure sooner in comparison to the other grafts. However, the graft donor site pain with kneeling down and certain other activities are the risks associated with the use of this graft. The least graft donor site morbidities are noticed when hamstring tendons are used as grafts. In the long term, with proper rehabilitation, all grafts behave similarly in terms of strength, stability and return to activities.

Type of Implants: The graft fixation is usually achieved by using either the titanium buttons or PEEK (Thermoplastic polymer) or Bio- interference screw (poly L-lactic acid (PLLA)). The graft material such as bio-screw although is more appealing can actually cause inflammatory reaction, liquefaction and widening of the tunnel in some individuals leading to loosening or laxity of the implant. The PEEK material is inert and usually gives good outcomes however in some individuals can still cause some widening of the tunnel.

Understanding these factors, let us try to understand what to expect post ACL surgery.

1. Full Recovery Timeline
   Recovering from ACL surgery typically takes around 6 to 12 months. During this period, patients undergo extensive physical therapy aimed at rebuilding strength, flexibility, and range of motion in the knee. The recovery process is gradual, and adherence to prescribed exercises is crucial to achieving optimal results. For athletes and active individuals, returning to sports usually occurs within the same 6 to 12-month timeframe, though this should be approached cautiously and incrementally to avoid re-injury.

   Function and Stability
   After ACL surgery and proper rehabilitation, most individuals experience significant improvement in knee stability. The common sensation of the knee “giving way” often resolves as strength and coordination are restored. With consistent physical therapy, patients typically regain full range of motion and strength. However, some may encounter mild limitations in flexibility or strength compared to their pre-injury level, particularly if rehabilitation is incomplete.

   Risks and Complications
   Although the surgical graft provides stability to the knee, there remains a small risk of re-injury, especially for individuals who return to high-impact activities prematurely. Adhering to a comprehensive rehabilitation program, which includes advanced techniques such as landing training and proprioception exercises, is vital for minimizing this risk. Additionally, ACL injuries can slightly increase the likelihood of developing knee arthritis in the long term. However, early surgical intervention and consistent rehabilitation can help mitigate this risk.

   Possible Limitations
   While most people regain confidence and functionality in their knee, some may occasionally experience discomfort or a sense of instability, particularly during high-impact activities. These limitations are often associated with incomplete adherence to rehabilitation programs. Although the knee may not feel identical to its pre-injury state, proper recovery protocols typically result in good strength and dependable knee function.

   Long-Term Outlook
   With time and proper training, most individuals achieve excellent strength and functionality in their knee, allowing them to participate in daily activities and return to active sports. In the long term, a well-healed ACL can perform much like a normal knee. Maintaining strong muscles around the knee and adhering to medical advice to prevent overuse or re-injury are key factors in ensuring the knee remains healthy and reliable over time.