It is often possible to walk with a torn anterior cruciate ligament (ACL). While some individuals may manage to walk in straight lines following such an injury, others might experience pronounced pain and instability that prevents any weight-bearing. This article explores why walking can occur after an ACL tear and outlines the necessary actions to take if such an injury is suspected.
The Role of the ACL and How it Tears
The anterior cruciate ligament (ACL) connects the thigh bone (femur) to the shin bone (tibia) within the knee joint. Its primary function is preventing the tibia from sliding too far forward under the femur and providing rotational stability to the knee.
ACL tears commonly occur during activities involving sudden stops, changes in direction, pivoting, or awkward landings from jumps. Non-contact injuries, like rapid deceleration with the foot planted, cause many ruptures, though direct impact can also lead to a tear. Because the ACL’s main role is in rotational and forward-backward stability rather than direct weight-bearing, some individuals can walk in a straight path even with a torn ligament.
Immediate Impact on Walking Ability
Following an ACL tear, individuals often report a distinct “pop” or “snap” sound or sensation in the knee. This is typically accompanied by immediate, severe pain and rapid swelling, which can develop within six hours due to internal bleeding. The knee may also feel warm, and many experience a sensation of the knee “giving way” or feeling unstable, making weight-bearing difficult.
Despite these symptoms, walking ability varies. Some can walk in straight lines, and even climb stairs, once initial pain and swelling subside. This is because other surrounding structures and muscles can sometimes maintain straight-line stability. However, activities involving turning, twisting, or pivoting often remain challenging and can cause the knee to buckle.
The extent of the tear, whether partial or complete, also influences immediate walking ability. A partial tear, where the ligament is stretched but not fully severed, might allow more immediate function than a complete rupture. Even if walking is possible, a noticeable loss of range of motion and persistent instability are common.
Risks of Walking and Essential Next Steps
Continuing to walk or place weight on a knee with a suspected ACL tear carries several risks. The primary concern is increased instability, which can lead to the knee “giving out” unexpectedly. This instability can cause further damage to other structures within the knee, such as the meniscus or articular cartilage, potentially accelerating the development of osteoarthritis. Walking on an unstable knee can also exacerbate pain and swelling, making recovery more challenging.
If an ACL tear is suspected, immediate action is important to manage symptoms and prevent additional injury. The RICE protocol (Rest, Ice, Compression, Elevation) is commonly recommended as a first aid measure. Rest the injured knee, often requiring crutches or a brace, to avoid activities that cause pain or instability. Apply ice to the knee for 15-20 minutes every few hours to reduce pain and swelling. Use compression with an elastic bandage to limit fluid buildup, and elevate the injured leg above heart level to promote drainage and reduce swelling.
Seeking prompt medical attention is essential for a proper diagnosis. A healthcare provider will conduct a physical examination, which may include specific tests to assess knee stability, such as the Lachman test. Imaging tests, particularly magnetic resonance imaging (MRI), are often used to confirm an ACL tear, determine its severity, and identify any co-occurring injuries. X-rays may also be taken to rule out bone fractures.
Regaining Stability and Normal Walking
Regaining stable and normal walking after an ACL tear typically involves a structured rehabilitation approach. Physical therapy plays a central role in this process, focusing on restoring knee function, increasing range of motion, and strengthening the muscles surrounding the knee, such as the quadriceps and hamstrings. These exercises help to improve proprioception, which is the body’s awareness of its position and movement, allowing other muscles to compensate for the torn ligament’s reduced stability.
For some individuals, particularly those who wish to return to high-demand activities or sports involving pivoting and cutting, surgical reconstruction of the ACL may be recommended. This procedure involves replacing the torn ligament with a tissue graft. Following surgery, physical therapy continues to be important, with a gradual progression to weight-bearing and walking, often starting with crutches and a brace. The goal of both surgical and non-surgical approaches is to restore sufficient knee stability to allow for confident, stable walking and to reduce the risk of future instability episodes or further joint damage. Adhering to professional medical and physical therapy guidance throughout recovery is important for achieving optimal outcomes.