After a total knee replacement (TKA), the body naturally forms scar tissue around the new joint. When this process becomes excessive, it is known as arthrofibrosis and is a common reason for a stiff knee after surgery. This aggressive scarring can severely limit the knee’s range of motion, preventing it from fully straightening (extension) or bending (flexion). Specific interventions are required to remodel this excess fibrous tissue and restore function.
Understanding Post-Surgical Fibrosis
Stiffening results from the body attempting to repair surgical trauma by laying down dense, fibrous material composed primarily of collagen fibers. This abnormal accumulation of scar tissue forms adhesions in the joint capsule and around the prosthetic components, physically restricting movement. Patients typically notice a progressive loss of the ability to bend or straighten the knee, often accompanied by persistent pain and swelling. This stiffness usually presents within the first few months after the operation. If left unaddressed, the dense collagen fibers become highly organized and much harder to stretch or break apart.
Therapeutic Exercises and Mobilization Techniques
The primary approach to breaking down fibrous tissue involves consistent, high-intensity therapeutic exercises performed multiple times daily. The mechanical force of prolonged stretching is necessary to physically remodel the dense, cross-linked collagen fibers. This is achieved through low-load, long-duration stretching, where a moderate force is applied for an extended time to encourage plastic deformation rather than just elastic stretch.
Specific exercises focus on regaining both flexion and extension. For extension, a patient might perform a prone hang, allowing gravity to gently stretch the knee into full straightness for several minutes. To improve bending, heel slides are crucial, often performed with a strap or towel to apply overpressure once the maximum active bend is reached. This manual assistance provides the prolonged, static stretch needed to lengthen the tightened tissues.
Manual and Assisted Mobilization
Physical therapists also employ manual therapy techniques, such as deep tissue massage, to target scar tissue beneath the skin and within the joint capsule. Patellar mobilization is an important technique, involving the therapist gently pushing the kneecap in various directions to prevent soft tissues from adhering to the underlying bone. Some surgeons may prescribe a Continuous Passive Motion (CPM) machine for use at home. The CPM provides rhythmic, gentle movement for several hours a day, which helps inhibit the formation of new adhesions in the immediate post-operative phase.
Advanced Medical Interventions
If aggressive physical therapy fails to restore sufficient range of motion, a physician may recommend procedures to mechanically disrupt the adhesions. The most common intervention is Manipulation Under Anesthesia (MUA), performed in an operating room while the patient is sedated. During MUA, the surgeon forcefully bends and straightens the knee joint to physically break apart the internal scar tissue bands restricting movement.
MUA is most effective when performed within six to twelve weeks, generally no later than three to six months after the original surgery. After this period, the scar tissue matures, becoming tougher and increasing the risk of complications like fracture. Following MUA, immediate and intensive physical therapy is mandatory to maintain the gained range of motion, as the body quickly attempts to reform scar tissue.
Adjunctive Treatments
Targeted injections of corticosteroid or anesthetic agents may be used to manage localized pain and inflammation. Reducing pain allows the patient to participate more fully in rehabilitation exercises.
Surgical Solutions and Managing Expectations
When all non-surgical methods, including MUA, fail to restore functional range of motion, the definitive option is arthroscopic lysis of adhesions, or arthrolysis. This procedure involves the surgeon inserting a small camera and instruments to visualize and precisely cut away the dense, fibrotic bands of scar tissue. This minimally invasive technique allows the surgeon to debride adhesions from the suprapatellar pouch, the gutters of the knee, and around the prosthetic components.
This intervention is typically reserved for patients who have plateaued in recovery for six to twelve months despite diligent therapy and MUA. Patients must understand that the surgery restarts the body’s healing process, creating a risk for new scar tissue formation. To prevent recurrence, immediate and aggressive physical therapy is required following the arthrolysis, often starting the same day. The long-term prognosis is generally favorable after a successful arthrolysis, but it necessitates a complete commitment to a rigorous post-operative rehabilitation protocol.