The goal of total knee arthroplasty (TKA) is to restore mobility and eliminate chronic pain, but persistent stiffness is a frustrating complication that limits function for many patients. This lack of full range of motion can make simple activities like climbing stairs or getting out of a chair a daily challenge. Regaining movement requires a proactive approach, combining intensive physical therapy with medical or surgical interventions when necessary. Understanding the cause of the restriction is the first step toward finding an effective solution to maximize the long-term success of the replacement.
Why Post-Replacement Stiffness Occurs
The primary reason for stiffness after a total knee replacement is the body’s natural healing response to surgical trauma, which can lead to the formation of excessive scar tissue. This condition is medically known as arthrofibrosis, where fibrous tissue develops within the joint, restricting the movement of the prosthetic components and surrounding soft tissues. If not managed with early motion, the scar tissue can mature and become dense.
Inadequate or delayed physical therapy is a significant contributing factor, as joint immobility allows the fibrous adhesions to set and tighten. Lack of sufficient pain control can also prevent a patient from engaging in necessary range-of-motion exercises. A stiff knee is often clinically defined as having less than 90 to 100 degrees of flexion, or an inability to fully straighten the leg.
Less commonly, mechanical issues can contribute to movement restriction. These factors include component malalignment, incorrect sizing of the prosthetic parts, or a postoperative infection. In these instances, stiffness is a symptom of a structural problem rather than a soft-tissue healing issue. A thorough evaluation is necessary to distinguish between scar tissue and mechanical causes before proceeding with treatment.
Conservative Strategies for Restoring Movement
The first and most important strategy for overcoming stiffness is intensifying the physical therapy regimen, which must be consistent and highly focused on regaining both flexion and extension. Frequency is paramount, with patients often needing to perform exercises multiple times a day to continuously stress the scar tissue and prevent it from reforming. This dedication to motion, even when uncomfortable, is the foundation of recovery.
High-yield exercises should be performed daily to stretch the restricted tissues. For increasing knee flexion, heel slides, where the patient actively pulls the heel toward the buttocks, are particularly effective. Using a stationary bicycle helps apply continuous, rhythmic tension to the joint capsule and surrounding muscles.
To improve extension, or the ability to fully straighten the leg, prolonged static stretching like prone hangs can be utilized. This involves supporting the heel off the end of a bed with a weight placed on the thigh to apply a gentle, sustained force.
Strategically managing pain is a component of successful rehabilitation, as it allows the patient to tolerate the necessary intensity of the exercises. Taking prescribed pain medication or nonsteroidal anti-inflammatory drugs (NSAIDs) shortly before a therapy session can reduce discomfort enough to achieve a greater range of motion during the stretching period. This preemptive use of medication is intended to maximize the therapeutic window rather than simply mask the pain.
The proper application of temperature therapy can further support physical therapy efforts. Applying moist heat for 15 to 20 minutes before exercise helps warm the soft tissues, making them more pliable and receptive to stretching. Conversely, using ice packs immediately after an intense session helps reduce localized inflammation and swelling. Consistency and commitment to these daily techniques often determine the final range of motion achieved.
Medical and Surgical Interventions for Severe Stiffness
When several months of intensive conservative management fail to achieve a functional range of motion, specialized medical procedures are considered as the next step. The most common first-line procedure is Manipulation Under Anesthesia (MUA), which is typically reserved for cases where the stiffness is due to arthrofibrosis and is performed within the first three to six months post-surgery for the best outcomes. During an MUA, the patient is placed under general anesthesia, and the surgeon manually and forcefully bends and straightens the knee to break up the restrictive scar tissue and adhesions.
Immediate and aggressive follow-up after MUA is necessary to maintain the motion gained. Patients are immediately started on intensive physical therapy, often utilizing a continuous passive motion (CPM) machine to keep the joint moving and prevent scar tissue reformation. Studies indicate that a significant gain in range of motion, often between 26 and 47 degrees, can be achieved with MUA.
If stiffness persists following an MUA, or if the procedure is no longer advisable due to the chronicity of the scar tissue, a surgical intervention may be required. Arthroscopic Lysis of Adhesions (LOA) is a minimally invasive surgical procedure where a surgeon uses small incisions and a camera to directly visualize and surgically cut away the bands of fibrous scar tissue. This procedure allows for the removal of adhesions from all compartments of the knee joint, often resulting in a significant improvement in the arc of motion.
Corticosteroid injections may be used in some cases to help reduce local inflammation associated with scar tissue formation, usually in conjunction with intensive therapy. For the rarest and most complex cases, where stiffness is caused by a mechanical issue such as a malpositioned or loose implant, revision surgery becomes the final option. These advanced interventions are designed to address the underlying cause of the persistent stiffness and restore maximum function.