Total knee arthroplasty (TKA) is a highly effective procedure for restoring mobility and relieving chronic pain. Following this major surgery, patients universally experience swelling, known clinically as edema, around the joint, often extending into the lower leg. This fluid accumulation is an expected part of the body’s response to surgical trauma. Understanding the biological reasons and typical timeline helps manage expectations during recovery.
The Biological Cause of Postoperative Swelling
The primary cause of swelling after knee replacement is the body’s natural inflammatory response to surgical trauma. During the procedure, the cutting and manipulation of bone and soft tissues triggers a cascade of healing mechanisms. This process increases blood flow to the area, causing fluid, white blood cells, and repair substances to leak from the capillaries into the surrounding tissues.
This fluid accumulation is compounded by a temporary disruption of the lymphatic system, which drains excess fluid and waste. Surgical incisions and tissue handling temporarily impair these vessels, slowing the clearance of fluid build-up. Additionally, post-operative immobility diminishes the “pumping action” of the calf muscles, which normally helps return fluid to the heart. The combination of increased fluid production and decreased fluid removal leads to puffiness in the knee and lower leg.
The Typical Timeline for Swelling Reduction
Swelling after TKA follows a predictable, multi-phase timeline, though duration varies between individuals. The initial, or acute, phase occurs in the first week, typically peaking around the third to fifth post-operative day. During this time, the knee is often puffy, warm, and bruised due to the immediate inflammatory reaction.
The subacute phase starts around the second week and continues until approximately six weeks post-surgery. Throughout this period, the overall volume of swelling noticeably decreases, though it remains significant, especially after periods of activity or at the end of the day. Consistent use of ice, elevation, and gentle movement aids resolution.
The long-term resolution phase extends from about three to six months, with residual swelling becoming mild and intermittent. Patients may only notice minor puffiness after intense physical therapy sessions or prolonged standing. While the majority of swelling resolves by six months, a minor degree of residual swelling can persist for up to a full year.
Strategies for Managing and Reducing Swelling
Effective management of post-operative edema relies on consistent, patient-controlled interventions. Elevation uses gravity to drain fluid away from the knee. The operated leg should be raised so the ankle is positioned above the level of the heart, using pillows to support the heel or ankle, not directly under the knee.
Applying cryotherapy (ice) regularly helps constrict local blood vessels and reduce the inflammatory response. Protocols recommend applying an ice pack for 15 to 20 minutes at a time, using a cloth barrier, and repeating every one to two hours, particularly after exercise. Compression garments, such as elastic bandages or specialized stockings, provide external pressure that prevents excessive fluid accumulation.
Gentle, prescribed physical therapy exercises, like ankle pumps, are also necessary. Movement of the ankle and foot activates the calf muscles, which act as a pump to encourage the return of venous blood and lymphatic fluid back toward the torso.
Warning Signs Requiring Medical Attention
While mild to moderate swelling is a normal part of recovery, certain signs indicate a serious complication requiring immediate consultation with a surgeon. A sudden, rapid increase in swelling days or weeks after the initial peak, accompanied by high fever, chills, or worsening pain, can signal a prosthetic joint infection.
Local signs of infection include intense redness and warmth radiating outward from the incision site, or thick, foul-smelling discharge or pus. Another serious complication is deep vein thrombosis (DVT), a blood clot in the leg veins. Symptoms of DVT include sudden calf pain or tenderness, or swelling dramatically worse in the operated leg, sometimes extending above the knee.