Anterior cruciate ligament (ACL) surgery reconstructs a torn knee ligament to restore stability and function. Regaining knee flexion (bending) is a significant part of recovery. This gradual return to full range of motion progresses from gentle movements to dynamic exercises over months. Understanding this progression and influencing factors aids rehabilitation.
Immediate Post-Surgery: The Initial Phase of Bending
In the first few weeks following ACL surgery, focus is on protecting the graft while initiating knee movement. Patients aim for about 90 degrees of knee bending by the end of the first week. This initial flexion is controlled, often guided by a physical therapist or a continuous passive motion (CPM) machine. A CPM machine slowly moves the knee through a pre-set range, reducing stiffness and improving mobility without active muscle engagement.
Goals include minimizing pain and swelling, which can limit movement. Gentle heel slides, where the heel is slid towards the buttocks, are common exercises to regain controlled knee flexion. Controlled movement is safe and prevents excessive scar tissue formation. Maintaining full knee extension (straightening the leg completely) is prioritized during early weeks to prevent long-term stiffness.
Progressive Bending: Weeks and Months After Surgery
As healing progresses (from week 4 onwards), focus shifts to increasing knee bending. By week 4 to 6, many patients aim for 130 to 140 degrees of knee bending. Full knee flexion (approximately 135 degrees) is a goal reached over months of rehabilitation. This progression involves active bending (using one’s own muscles) and assisted stretches.
Weight-bearing activities are introduced and increased as tolerated, contributing to knee strengthening and flexibility. Exercises like seated knee bends, wall slides, and stationary bicycling improve and maintain flexion. The timeline for full bending varies among individuals, influenced by healing rates and adherence to rehabilitation protocols. Consistent effort and physical therapist guidance are important to meet these milestones.
Key Factors Influencing Your Bending Timeline
Several elements influence how quickly an individual regains knee bending after ACL surgery. The type of graft used plays a role; common options include patellar tendon, hamstring tendon, or quadriceps tendon autografts, and allografts. Each graft type may have different implications for strength deficits in the harvest site, affecting the rehabilitation timeline. For example, hamstring tendon grafts can lead to greater knee flexion strength deficits early on.
Other knee injuries, such as meniscus tears or cartilage damage, also impact the bending timeline. If a meniscal repair is performed alongside ACL reconstruction, weight-bearing restrictions and knee flexion limitations might be more stringent to protect the healing meniscus. Healing rates, which vary widely, are another factor, as is adherence to post-operative instructions and the physical therapy program. Post-surgical complications, such as infection or arthrofibrosis, can impede knee bending recovery. Arthrofibrosis is excessive scar tissue formation within the joint, leading to painful motion restriction.
The Role of Physical Therapy and Safe Progression
Physical therapy is fundamental to successful knee bending recovery after ACL surgery. Therapists design individualized programs guiding patients through a structured progression of exercises, ensuring safe and effective movements. They monitor range of motion, pain, and swelling, adjusting exercises as needed. Techniques like heel slides, wall slides, and specific stretches improve flexibility.
Pushing the knee too hard or too soon can strain the graft, increase swelling, and cause pain, potentially delaying recovery or leading to re-injury. Conversely, insufficient knee movement can result in stiffness, scar tissue formation (arthrofibrosis), and prolonged recovery. Physical therapists help patients find the right balance, providing manual therapy, educating on proper body mechanics, and teaching self-mobilization techniques. Listening to the physical therapist and one’s body signals is key for safe, effective return to full knee function.