MUA stands for manipulation under anesthesia, a non-invasive medical procedure where a doctor physically moves a stiff joint through its full range of motion while you’re sedated. The goal is to break up scar tissue and adhesions that are restricting movement, particularly after a joint replacement or in cases of frozen shoulder. Because you’re under anesthesia, your muscles are fully relaxed, allowing the doctor to push the joint past the point where pain and muscle guarding would normally stop you.
Why MUA Is Performed
MUA is used when a joint has become stiff and unresponsive to standard treatments like physical therapy, pain medication, and steroid injections. The procedure has been part of musculoskeletal medicine for decades and is most commonly performed on two joints: the knee and the shoulder.
After a total knee replacement, some patients develop a condition called arthrofibrosis, where scar tissue binds together tissues inside the knee that aren’t normally connected. This makes the knee feel tight and painful, and it limits how far you can bend or straighten it. If your knee can’t reach 90 degrees of flexion (the amount needed to climb stairs or get out of a chair comfortably) within the first several weeks after surgery, your surgeon may recommend MUA.
For the shoulder, MUA is most often used to treat adhesive capsulitis, commonly known as frozen shoulder. This condition causes the capsule of tissue surrounding the shoulder joint to thicken and tighten, progressively limiting your ability to raise your arm or rotate it outward. When months of conservative treatment haven’t restored adequate movement, MUA can break through those restrictions in a single session.
What Happens During the Procedure
MUA is not surgery. There are no incisions, and it’s not classified as an operation. You’re placed under general anesthesia with full muscle relaxation, though in rare cases a spinal block is used instead. Once you’re sedated and your muscles are completely relaxed, the surgeon carefully and deliberately moves the joint through progressively larger arcs of motion. This controlled force stretches and breaks the adhesions that have been limiting your range.
The procedure itself is brief, typically lasting only minutes. The key is the combination of anesthesia and skilled force: without the muscle guarding that your body reflexively uses to protect a painful joint, the surgeon can achieve motion that would be impossible while you’re awake. Afterward, you’re monitored in a recovery area as the anesthesia wears off.
How Well It Works
For knee stiffness after a total knee replacement, the results can be dramatic. In a multicenter clinical trial, patients who started with an average range of motion of just 72 degrees gained 46 degrees immediately after MUA, reaching 118 degrees on the table. At one year, patients maintained a 37-degree improvement over their pre-MUA baseline. The best outcomes occur when MUA is performed within 12 weeks of the original surgery, before scar tissue has fully matured and hardened.
For frozen shoulder, 94% of patients reported satisfaction with MUA in one study, with pain and function scores nearly tripling from before the procedure. Forward flexion (raising your arm in front of you) reached an average of 156 degrees at three months, and external rotation continued improving out to 12 months. A small number of patients may experience recurrent stiffness and need a follow-up steroid injection, but this is uncommon.
Recovery and Physical Therapy
What happens after MUA matters as much as the procedure itself. The motion gained on the table will be lost if you don’t begin aggressive physical therapy almost immediately. Most protocols call for starting therapy within one to two days, and continuing three times per week. You’ll also be given a home exercise program to maintain and build on the range of motion achieved during the manipulation.
The first few weeks of rehab can be uncomfortable. Your joint has just been forced through a range it hasn’t experienced in weeks or months, and there will be swelling and soreness. But skipping or delaying therapy risks letting new adhesions form, which defeats the purpose of the procedure entirely. Consistency in this early window is the single biggest factor in a successful outcome.
Risks and Contraindications
Because no incisions are made, MUA carries fewer risks than surgical alternatives like arthroscopic scar tissue removal. The primary concerns are bone fracture (particularly in patients with weakened bones), nerve or blood vessel injury, and tearing of surrounding soft tissues. These complications are rare when the procedure is performed by an experienced surgeon who applies force gradually and within safe limits.
Not everyone is a candidate. Osteoporosis is a relative contraindication because fragile bones are more likely to fracture under the force required. Active infection in or around the joint is an absolute disqualifier, as is an implant that was incorrectly positioned or sized during the original surgery. If the stiffness is caused by a mechanical problem with the implant itself, MUA won’t fix it, and a revision surgery may be needed instead. Your surgeon will typically order imaging and lab work beforehand to rule out these issues.
Insurance Coverage
Most insurers cover MUA when it’s deemed medically necessary, but there are specific criteria you’ll need to meet first. For frozen shoulder, insurers like Aetna require at least 12 weeks of documented conservative treatment that hasn’t worked, including pain medication or corticosteroids, physical therapy, and at least one steroid injection into the joint. For post-surgical knee stiffness, the threshold is generally a range of motion below 90 degrees despite consistent rehabilitation efforts. Your surgeon’s office will typically handle the prior authorization process, but knowing these benchmarks can help you understand the timeline.