The healing process following a total knee replacement (TKA) involves a natural inflammatory response. In some individuals, this response leads to the excessive formation of dense, fibrous tissue, known as arthrofibrosis or “stiff knee syndrome.” This scar tissue, composed primarily of collagen fibers, forms adhesions that bind tissues that should normally move freely. This scarring restricts the ability to fully bend or straighten the knee, limiting range of motion and causing chronic pain. Early intervention is important because persistent stiffness severely hinders rehabilitation and the ability to perform daily activities.
Physical Therapy and Targeted Exercises
Physical therapy is the initial strategy for managing and preventing excessive scar tissue formation after knee replacement. The focus is on regaining a full, functional range of motion (ROM) through consistent, low-impact movements that gently stretch the joint and surrounding soft tissues. Early and regular stretching helps mold the developing scar tissue, ensuring it remains pliable rather than dense and restrictive. Patients are instructed to perform exercises multiple times daily to sustain the flexibility gains achieved during formal therapy sessions.
Achieving full knee extension, or the ability to completely straighten the leg, is a primary aspect of recovery. The prone hang is a highly effective home exercise that utilizes gravity to apply a sustained, passive stretch. The patient lies face down on a bed, allowing the lower leg to hang off the edge. A small towel is placed under the thigh just above the kneecap for support, and the position is held for several minutes to gently pull the knee into extension.
Restoring the ability to bend the knee (flexion) is equally important for activities like climbing stairs or sitting down. Heel slides are a foundational exercise where the patient, lying on their back, slowly slides their heel toward their buttocks, bending the knee as far as comfortable. Stationary cycling is a low-impact activity that systematically works both flexion and extension, making it a valuable recovery tool. Patients can often begin using a stationary bike as early as one to two weeks post-surgery, initially with the seat raised to minimize the required bend.
When using a stationary bike, the patient should pedal slowly with no resistance, focusing on the continuous, fluid motion of the joint. Beginning in reverse can sometimes initiate movement more easily, and the seat can be gradually lowered as flexibility improves to increase flexion. Physical therapists also employ manual therapy techniques, applying controlled pressure and massage to the incision area and surrounding soft tissues. While manual manipulation does not break up dense internal scar tissue, it improves blood flow, relaxes tight muscles, and frees up superficial layers of skin and fascia that contribute to overall stiffness.
Clinical Interventions for Scar Tissue Reduction
When conservative home therapy does not produce sufficient mobility gains, medical professionals may recommend clinical interventions to reduce inflammation and enhance physical therapy effectiveness. Pharmaceutical treatments mitigate the inflammatory response that drives scar tissue formation. Studies show that the perioperative use of nonsteroidal anti-inflammatory drugs (NSAIDs) and oral corticosteroids reduces the risk of developing arthrofibrosis. This also lowers the need for subsequent procedures, such as manipulation under anesthesia.
Intra-articular corticosteroid injections (CSI) are a common non-surgical option, administered directly into the joint space or surrounding soft tissue. Corticosteroids calm the local immune response, providing a powerful, short-term reduction in inflammation, pain, and swelling. This reduction in discomfort creates a temporary window for the patient to push harder in physical therapy and achieve greater range of motion. However, this approach carries a risk of infection, which is a significant concern in a joint with an artificial implant.
Advanced physical therapy incorporates specialized equipment and techniques that go beyond routine home exercises. Continuous Passive Motion (CPM) machines are sometimes used early postoperatively to gently move the knee through a controlled arc while the patient rests. Therapists also utilize high-grade joint mobilization, which involves applying sustained, forceful pressure at the end of the joint’s available range of motion. This aggressive stretching is intended to induce a plastic deformation in the tight joint capsule and soft tissues.
Emerging treatments, such as regenerative tissue injections, are being explored for their potential to manage arthrofibrosis. These injections may contain anti-inflammatory agents and growth factors that promote a more regulated healing environment. This approach aims to reduce the formation of new scar tissue by modulating the inflammatory process. It offers an alternative to traditional steroid injections.
Surgical Solutions for Severe Arthrofibrosis
For the minority of patients whose knee stiffness persists despite months of aggressive physical therapy and clinical interventions, surgical procedures are the necessary last resort. The most common approach is Manipulation Under Anesthesia (MUA), typically performed within the first three months after the initial TKA. The patient receives general anesthesia, which relaxes the muscles and eliminates pain. This allows the surgeon to forcefully bend and straighten the knee, applying controlled force designed to break the internal fibrous adhesions restricting movement.
If significant stiffness persists beyond three to six months, or if a large mass of scar tissue is suspected, the surgeon may recommend an arthroscopic lysis of adhesions (ALA). This procedure uses a small camera and specialized surgical instruments inserted through tiny incisions. The surgeon visualizes and surgically cuts away the thick bands of scar tissue within the joint. ALA allows for the direct removal of restrictive fibrous tissue, which is necessary when scar tissue is too mature or extensive for manipulation alone.
Following either MUA or ALA, extremely intensive physical therapy must begin immediately to maintain the motion achieved. If the newly gained range of motion is not rapidly utilized, the inflammatory response can cause the scar tissue to quickly re-form. This leads to a recurrence of stiffness.