Knee stiffness after knee replacement: when is manipulation under anesthesia considered?

Knee replacement creates a large healing response. Fluid, warmth, bruising, pain, and temporary weakness can make the knee feel tight even when the implants are functioning normally. Motion often varies from one day to the next. A more active day may be followed by extra swelling and less bending.

Recovery is not judged by one uncomfortable therapy session or one measurement. Your preoperative motion, the reason for surgery, prior operations, pain control, swelling, wound healing, and ability to participate in rehabilitation all matter. The knee replacement recovery timeline explains what commonly changes across the first year.

There is no single motion number that defines stiffness for every patient. Surgeons consider both flexion, or bending, and extension, or the ability to straighten. They also ask what the limitation prevents you from doing. Trouble rising from a chair, using stairs, getting into a vehicle, sleeping comfortably, or walking with a normal stride may be more meaningful than a number alone.

The pattern matters. A knee that is steadily gaining motion is different from one that plateaued for several weeks or is losing motion. A knee that was very stiff before surgery may have a different realistic target than a knee that moved fully before surgery.

Excess scar formation, often called arthrofibrosis, is one possible cause. It is not the only one. Pain that prevents movement, uncontrolled swelling, a healing problem, infection, a fracture, tendon injury, nerve-related pain, component position, joint-line or soft-tissue balance, and a true mechanical block can all limit motion. A 2025 diagnostic review emphasized distinguishing arthrofibrosis from infection, malalignment, and mechanical causes before choosing treatment. Review the diagnostic overview.

This is why simply pushing harder is not always the answer. Treatment should be directed at the reason the knee is not moving.

The evaluation starts with the motion trend and the details of recovery. Your surgeon may review therapy measurements, pain and medication needs, swelling, wound appearance, walking, falls, and whether motion improved and then declined. The examination assesses flexion, extension, stability, strength, patellar movement, tenderness, warmth, and the quality of the endpoint when the knee is gently moved.

Updated X-rays may be appropriate when the cause is unclear or progress is unexpectedly poor. Blood tests and, in selected cases, joint aspiration may be used when infection is a concern. Other testing depends on the history and examination. Manipulation should not be used as a shortcut around this workup.

When there is no urgent complication or mechanical block, the first plan often focuses on swelling control, safe pain management, frequent short periods of motion, walking, and appropriately progressed physical therapy. The goal is useful movement without repeatedly provoking so much pain and swelling that the next session becomes harder.

Rehabilitation should be individualized. More force is not always better. A patient who is guarding because of severe pain, dizziness, medication effects, or poor sleep may need those barriers addressed. Follow the prescribed program rather than adding aggressive devices or exercises without guidance.

Manipulation under anesthesia, commonly shortened to MUA, is a procedure performed while you are anesthetized so the muscles are relaxed and you do not feel the maneuver. The surgeon carefully moves the knee through a controlled range to stretch or release restrictive scar tissue. It usually does not require a new surgical incision.

MUA is not routine after knee replacement. It is considered when motion remains meaningfully limited or has stopped improving despite an appropriate rehabilitation plan, and when the evaluation does not show a problem better treated another way.

Scar tissue can mature and become more resistant over time, so a sustained plateau should be discussed rather than ignored for months. A 2024 systematic review comparing early and delayed MUA found that both groups improved, but early MUA produced a larger average gain in flexion and the delayed group had higher reported complication and revision rates. Read the systematic review.

This does not create an automatic deadline. Later MUA may still help selected patients, and early MUA is not appropriate when the diagnosis is uncertain. Timing should reflect the motion trajectory, the cause of stiffness, wound and medical status, risks, and whether reasonable nonoperative steps have been given a fair chance.

The intended benefit is improved motion and function. The amount of improvement varies, and some motion gained in the operating room can be lost if pain, swelling, or recurrent scar formation prevents continued movement afterward. MUA cannot correct a poorly positioned implant, infection, fracture, or another mechanical problem.

Risks include increased pain and swelling, bleeding into the joint, fracture, wound problems, tendon or ligament injury, blood clot, anesthesia complications, and recurrent stiffness. Serious complications are uncommon, but they matter. Your individual bone quality, implant fixation, medical conditions, and time since surgery may change the risk.

A plan for pain control, swelling management, and rehabilitation should be arranged before the manipulation. Therapy and home motion usually resume promptly, but the exact schedule is individualized. The goal is to preserve useful motion while the irritated knee settles.

Ask how often to perform home exercises, when formal therapy will occur, what pain level is expected, and which symptoms should trigger a call. Do not drive while taking impairing medicine or until you can control the vehicle safely and have been cleared.

If stiffness is longstanding, MUA did not provide durable improvement, or testing identifies a mechanical problem, other options may be discussed. These can include arthroscopic or open removal of scar tissue and, in selected cases, revision knee replacement. The correct choice depends on the cause, not simply the degree of stiffness.

Revision surgery is a larger undertaking and should follow a systematic workup. The revision knee replacement guide explains how infection, loosening, instability, bone loss, component position, and stiffness affect that decision.

Contact the surgical team promptly for increasing wound drainage, spreading redness, fever, rapidly worsening pain, a new inability to bear weight, a fall with new deformity, or sudden loss of active knee extension. New calf pain or marked one-sided swelling needs prompt medical guidance because it can be a blood-clot warning sign.

Call 911 for chest pain, sudden shortness of breath, fainting, signs of stroke, or severe difficulty breathing. Do not drive yourself for emergency care.

Patients in Honolulu, elsewhere on Oahu, Kona, Hilo, and across Hawaii should keep a simple record of motion measurements, therapy progress, swelling, and the activities that remain difficult. Neighbor-island patients may be able to begin the discussion remotely, but an in-person examination and imaging may be needed before deciding on a procedure.

If your knee motion has plateaued, is worsening, or remains too limited for daily function, schedule an orthopedic consultation for a focused stiff-knee evaluation. Bring therapy measurements, prior operative records when available, and a current medication list.

• American Association of Hip and Knee Surgeons: Total Knee Replacement
• American Association of Hip and Knee Surgeons: Knee Exercises
• Akhtar M, et al. Outcomes of Early Versus Delayed Manipulation Under Anesthesia for Stiffness Following Total Knee Arthroplasty. 2024.
• Diagnosis and Clinical Assessment of Arthrofibrosis after Total Knee Arthroplasty. 2025.
• Revision for stiff knee after knee replacement. 2024.
• Multicenter randomized trial of adjunctive medication, MUA, and physical therapy after knee replacement. 2024.