Sunshine Coast Orthopaedic Group

Procedure · Knee · Stiffness after knee replacement

Manipulation under anaesthetic.

If a knee replacement stops bending in the early weeks, the knee is flexed under anaesthetic to break down forming scar tissue. Timing is the whole of it.

Call (07) 5493 8038 How it is performed
Reviewed by Professor Daevyd Rodda Orthopaedic Surgeon · MBBS, Dip. Surg Anat, FRACS, FAOrthA Last reviewed: 21 August 2026
What it is
Knee flexed under anaesthetic to release scar
When
Usually 6 weeks to 3 months after surgery
Anaesthetic
General or spinal
Stay
Day case or one night
Frequency
About 2 to 4% of knee replacements
Physiotherapy after
Immediate and intensive

What it is.

Stiffness is the complication most specific to knee replacement. In most patients the knee bends progressively over the first weeks. In a small proportion, roughly 2 to 4 percent, flexion stalls and then goes backwards.

The reason is arthrofibrosis: the body's healing response producing more scar tissue inside the joint than it needs. That scar is soft and remodelling in the early months, and becomes tougher and more established with time. A manipulation takes advantage of that window.

When it is recommended

Generally when flexion is stalling below about 90 degrees at six weeks, or where range is plateauing well below what was achieved at surgery despite consistent physiotherapy.

Timing matters more than almost anything else in this operation. Manipulation performed within the first three months is considerably more effective than manipulation performed later, because after that the scar is mature and forcing it risks fracture or damage to the extensor mechanism rather than releasing anything.

This is why patients are asked to call the rooms if flexion stalls, rather than waiting for the next scheduled review. A knee that is not bending at six weeks is a reason to be seen.

How it is performed.

  • Infection and any mechanical cause are excluded first. A stiff knee that is stiff because of a malpositioned component or an infection will not be helped by manipulation, and that needs establishing beforehand.
  • Under general or spinal anaesthetic, with the muscles fully relaxed, the knee is flexed in a slow controlled manner. The scar tissue gives way, often audibly.
  • The range achieved is recorded, and it is the target for physiotherapy to hold.
  • Usually a day case, sometimes one night for pain control.
  • Good analgesia afterwards is part of the plan, sometimes with a nerve block or an epidural, because the range gained is only kept if you can work through the first few days.

The manipulation is deliberately controlled rather than forceful. Excessive force risks fracture of the femur, rupture of the patellar or quadriceps tendon, or wound dehiscence.

Recovery timeline.

The manipulation buys a window. Physiotherapy keeps it.

  • Same day. Physiotherapy starts before you leave. This is not optional and it is not deferred to next week.
  • First week. Daily physiotherapy, often with a continuous passive motion machine, and strong analgesia so the range can be worked through.
  • Weeks 2 to 6. Continued intensive rehabilitation, tapering as the range holds.

The knee will be sore and swollen for a period afterwards. That is expected.

Outcomes.

Most patients gain meaningful flexion, and published series report average gains in the order of 30 degrees, with the majority of that retained. Results are better the earlier it is performed.

Some range is commonly lost again in the days afterwards, which is why the immediate physiotherapy matters so much. A proportion of patients do not hold the gain and a small number require a second manipulation or, rarely, arthroscopic or open release of the scar.

Recognised risks are uncommon but real: fracture of the femur, rupture of the patellar or quadriceps tendon, wound problems and bleeding into the joint. They are the reason the manipulation is controlled rather than forced, and the reason it is not attempted once the scar is mature.

Rehabilitation.

Intensive and immediate. The protocol is provided at the time and physiotherapists can request it through For Physiotherapists. The single message is that the days immediately after the manipulation determine whether the range is kept.

Questions worth asking at your consultation.

Every one of these is a fair question and none of them should be awkward to ask. Print them or bring them on your phone.

  • Am I a good candidate for manipulation under anaesthetic, and what would make me a poor one?
  • What are the alternatives, including doing nothing for now?
  • How many of these do you perform in a year?
  • What does the Australian registry say about the implant you would use for someone my age?
  • What does a realistic result look like for me specifically, and what will I still not be able to do?
  • What is your plan if it does not go well?

Frequently asked questions.

How do I know if my knee needs a manipulation?

If flexion is stalling below about 90 degrees at six weeks, or plateauing well below the range achieved at surgery despite consistent physiotherapy. Call the rooms rather than waiting for the next scheduled review.

Why does timing matter so much?

Scar tissue is soft and remodelling in the first three months and becomes mature and tough after that. A manipulation in the early window releases the scar; the same manoeuvre later risks fracturing bone or rupturing tendon instead.

Is it painful?

The manipulation itself is done under anaesthetic so you feel nothing at the time. The knee is sore and swollen afterwards, and good analgesia is part of the plan because you need to work through the range immediately.

Will the stiffness come back?

Some range is commonly lost in the days afterwards, which is why physiotherapy starts the same day and continues daily in the first week. Most patients retain a meaningful gain. A small number need a second manipulation or a surgical release.

Is a manipulation a sign something went wrong?

Not usually. Arthrofibrosis is a recognised response to surgery in a small proportion of patients and is not in itself evidence of a technical problem. Infection and mechanical causes are excluded before it is performed.

References.

  1. Pivec R, Issa K, Kester M, et al. Long-term outcomes of MUA for stiffness in primary TKA. J Knee Surg. 2013;26(6):405-410.
  2. Fitzsimmons SE, Vazquez EA, Bronson MJ. How to treat the stiff total knee arthroplasty? A systematic review. Clin Orthop Relat Res. 2010;468(4):1096-1106.

This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.