Total Knee Replacement (TKR) surgery is a common and generally successful procedure designed to relieve pain and restore function in a damaged knee joint. Normal healing involves forming some scar tissue necessary for tissue repair. However, an exaggerated healing response can lead to a complication known as arthrofibrosis. This condition involves the excessive buildup of dense, non-pliable fibrous tissue within and around the joint, restricting the smooth movement of the new knee components.
Identifying the Symptoms of Excessive Scar Tissue
The clearest indication of excessive scar tissue is severe, persistent stiffness that fails to improve despite consistent physical therapy several months after surgery. While some stiffness is expected during recovery, arthrofibrosis presents as a mechanical block rather than simple muscle tightness. This inability to fully use the knee often signals a deeper underlying issue.
A noticeable decline in the knee’s Range of Motion (ROM) is the hallmark symptom. Patients struggle to achieve full knee extension (straightening the leg) or lack sufficient flexion (bending the knee). Surgeons often look for passive flexion less than 90 degrees or an extension deficit greater than 10 degrees. These limitations severely restrict daily activities like climbing stairs or sitting comfortably.
The pain associated with arthrofibrosis is often chronic and deep-seated, unlike expected post-operative pain that diminishes steadily over time. Discomfort may worsen significantly when attempting to push the joint through its limited range of motion. Patients may also report a firm, nonfluctuant feeling in the knee, reflecting the dense, rigid tissue formation inside the joint capsule.
Observable signs include a persistent flexed-knee gait, where the patient walks with the knee slightly bent because scar tissue prevents full extension. This gait pattern compensates for stiffness but places abnormal stresses on other joints. Furthermore, the kneecap may feel less mobile or “stuck,” indicating that fibrous tissue has restricted the natural gliding motion of the patella over the femur.
Medical Confirmation and Diagnosis
If symptoms suggest excessive scar tissue, a thorough medical assessment is needed to objectively confirm the diagnosis and rule out other complications. The clinical assessment begins with a detailed, measured evaluation of active and passive Range of Motion (ROM). This evaluation, performed by the surgeon or physical therapist, quantifies the motion deficit and tracks its progression over time.
Imaging studies ensure stiffness is not caused by mechanical issues with the implant. Standard X-rays confirm that the knee replacement components are properly aligned and have not loosened or shifted. X-rays also allow the medical team to check for heterotopic ossification, which is the abnormal formation of bone outside the skeleton and another potential cause of stiffness.
To gain a clearer picture of soft tissues, advanced imaging like Magnetic Resonance Imaging (MRI) may be used, often utilizing specialized metal artifact reduction techniques. MRI can visualize the thickened, fibrous tissue within the joint capsule and surrounding soft tissues, helping confirm arthrofibrosis. However, diagnosis relies on integrating clinical findings with the exclusion of other possibilities, not imaging alone.
Before confirming arthrofibrosis, the medical team must systematically exclude other causes of a stiff, painful knee, such as low-grade joint infection or component malposition. Synovial fluid analysis may be performed to test joint fluid for infection markers, ensuring an infectious process is not driving inflammation and scarring. The diagnosis is typically reserved for a persistent ROM deficit, such as flexion less than 90 degrees, that remains for more than three months after surgery, after all other causes have been eliminated.
Options for Managing Arthrofibrosis
Once arthrofibrosis is confirmed, initial management focuses on conservative, non-surgical interventions to restore joint mobility. Aggressive, highly focused physical therapy is the primary starting point. This therapy utilizes specialized stretching, mobilization techniques, and sometimes dynamic splinting to soften and lengthen the restrictive scar tissue. This intensive approach aims to regain lost extension and flexion by applying sustained, controlled force to the joint.
If a patient fails to show meaningful improvement after several months of physical therapy, the surgeon may recommend Manipulation Under Anesthesia (MUA). This non-surgical intervention is performed while the patient is fully sedated. Sedation allows the surgeon to manually and forcefully flex and extend the knee, breaking up internal scar tissue adhesions without muscle guarding. MUA is most effective when performed relatively early, typically within three to six months following the initial TKR, before the fibrous tissue becomes too rigid.
For cases unresponsive to MUA or those presenting later with very dense scar tissue, surgical intervention is the next option. This procedure, called an arthroscopic or open arthrofibrosis release, involves the physical removal of the excessive fibrous tissue (lysis of adhesions) from inside the joint. The goal is to clear the mechanical obstruction and restore the necessary space for the implant to move freely.
Following surgical release, post-operative recovery immediately focuses on maintaining the newly achieved range of motion. This involves an aggressive physical therapy protocol, often including a Continuous Passive Motion (CPM) machine, to prevent the rapid re-formation of scar tissue. In the most severe and chronic cases, such as when component malposition contributes or scar tissue is extensive, a revision TKR may be necessary to achieve a functional, mobile joint.