Specific Risks of Total Knee Replacement

Part of The Joint Replacement Guide — Phase 3: Understanding the Risks · Article 15 of 42 · Knee

Key Points

• Stiffness, kneecap (patellar) problems, and persistent discomfort are the main risks specific to knee replacement.
• Knee replacement has a notably higher rate of ongoing mild discomfort than hip replacement, even when the operation has technically gone well — this is worth knowing about honestly in advance.
• Most stiffness responds to focused physiotherapy; a minority need further treatment.
• Understanding these risks in advance helps set realistic, well-informed expectations.

Stiffness

Stiffness is a more common complication of knee replacement than of hip replacement. It can result from an individual’s healing response (some people simply form more scar tissue than others, a process called arthrofibrosis), insufficient early rehabilitation, or significant stiffness already present before surgery. Intensive physiotherapy is the main treatment and resolves the majority of cases. If progress stalls — typically assessed around the six to twelve week mark — a manipulation under anaesthesia (MUA), where the knee is gently moved through its full range while you are anaesthetised, can be used to break down early scar tissue and improve movement. Further surgery for stiffness alone is rare.

Patellar (Kneecap) Complications

Problems can occasionally arise with how the kneecap tracks over the new joint, sometimes causing anterior (front of knee) pain or a sensation of instability. If the back of the kneecap has been resurfaced (see the dedicated article on patellar resurfacing later in this guide), a fracture of the resurfaced patella is a rare but recognised complication. These issues are relatively uncommon and are usually managed with physiotherapy in the first instance.

Persistent Pain — An Honest Conversation

This is one of the most important things to understand before knee replacement surgery. Even when a knee replacement is technically well-performed and functioning correctly on imaging, a meaningful minority of patients — commonly cited in the surgical literature as around one in five — report some degree of ongoing discomfort or dissatisfaction afterwards. This is a notably higher rate than after hip replacement, and the reasons are multifactorial: they can include how the nervous system has adapted to years of chronic pain before surgery (a topic covered in more depth later in this guide), unrealistic pre-operative expectations, and soft tissue causes of pain that are separate from the joint replacement itself. It doesn’t mean the surgery has “failed” — the vast majority of these patients still report meaningful overall improvement — but it is an important, honest part of informed consent for knee replacement specifically.

Other Knee-Specific Risks

Instability, related to how the ligaments around the new joint are balanced during surgery, can occasionally occur and may need further treatment if significant. Injury to the extensor mechanism — the patellar tendon that allows you to straighten your knee — is a rare but serious complication. Infection rates are broadly similar to, though in some registry data very slightly higher than, hip replacement, and are managed as described in the general surgical risks article.

In More Depth

The difference in patient satisfaction between hip and knee replacement is well documented in the surgical literature and reflects genuine differences between the two joints, rather than differences in surgical quality. The knee is a more mechanically complex joint, relying heavily on soft tissue balance (ligaments and the surrounding muscles) in addition to the bony replacement itself, whereas the hip is more of a simple ball-and-socket joint where restoring normal mechanics tends to produce more consistently excellent results. This is part of why realistic, individualised expectation-setting — covered later in this guide — is arguably even more important before knee replacement than before hip replacement.

This article is general information and does not replace individual clinical advice.

Sources

• National Joint Registry — Annual Report, knee replacement outcomes
• British Association for Surgery of the Knee (BASK) — patient information resources
• Systematic reviews of patient satisfaction following total knee replacement, surgical literature

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