Medically Reviewed by Dr Wang Lushun
Senior Consultant Orthopaedic Surgeon
MBBS (S’pore), MRCS (Edinburgh), MMed (Ortho), FRCS (Ortho) (Edinburgh)
A knee that suddenly buckles or gives way can make everyday movement feel uncertain. Some people notice it on the stairs or when changing direction, while others simply feel that they cannot trust their knee. Pain may be present, but an unstable knee does not always hurt.
There are several reasons why a knee may become unstable, and the cause is not always obvious from the sensation alone. Understanding what is behind the instability can help determine whether treatment is needed.
Knee instability refers to a feeling that the knee is unsteady or may give way during movement. It can occur occasionally or become frequent enough to affect everyday activities.
Some people describe a shifting sensation within the knee or feel less confident putting weight on the affected side. Pain or swelling may also be present in the knee, although instability can occur without either.
Knee instability and knee weakness can feel similar, but the underlying cause may differ. Weakness generally refers to reduced strength in the muscles supporting the knee, while instability may be related to structures such as the ligaments that help keep the joint stable.
Muscle weakness can also contribute to instability by reducing control of the knee during movement. An assessment can help distinguish between weakness and other causes of instability.
Knee instability can have several causes. In some cases, it begins after a clear injury. In others, it develops gradually as changes within the knee affect how well the joint functions during movement.
Ligament injuries are a common cause, particularly injuries to the anterior cruciate ligament (ACL). When the ACL is torn, the knee may become unstable during movements that involve turning or changing direction.
Other causes include:
Certain factors can make knee instability more likely, including:
Persistent knee instability can make certain activities increasingly difficult. Depending on the underlying cause, repeated episodes of giving way may also increase the risk of further injury within the joint.
For example, ongoing instability after an ACL injury can increase the risk of damage to the meniscus or cartilage. This does not mean that every unstable knee will worsen, but recurrent instability is worth assessing rather than simply adapting around it.
Diagnosing knee instability starts with understanding when the knee gives way and what tends to trigger it. The doctor will also ask about previous injuries and whether there are other symptoms, such as knee pain or swelling. Locking or catching may provide further clues about which structures are involved.
A physical examination can then help identify the likely source of the instability. Imaging may be recommended if a structural injury is suspected.
The examination will depend on the symptoms and how the instability began. The doctor may assess:
Treatment for knee instability depends on the underlying cause and how much the problem affects daily activities. The aim is to improve knee stability while addressing the problem responsible for the episodes of giving way.
Non-surgical treatment often focuses on improving the strength and control of the knee. This may include:
Surgery may be considered when knee instability persists despite appropriate non-surgical treatment or when an injury prevents the knee from remaining stable during important activities. Factors that may influence this decision include:
When a knee repeatedly gives way, identifying the underlying cause is important before deciding how it should be managed. An assessment can help determine what is causing the instability and whether treatment is needed.
At Arete Orthopaedic Centre, patients with knee instability can undergo assessment and receive treatment based on the cause and severity of their condition. Management may include non-surgical care such as physiotherapy and rehabilitation, as well as surgical treatment where appropriate.
Senior Consultant Orthopaedic Surgeon Dr Wang Lushun works with patients to determine an appropriate treatment approach based on their knee function and individual needs. If your knee keeps giving way or feels increasingly unreliable, schedule a consultation with us.
Some forms of exercise may still be possible, but activities that cause the knee to buckle or give way should generally be avoided until the cause is understood. The type and intensity of exercise that is suitable will depend on how stable the knee is and what is causing the problem.
Not everyone with knee instability requires imaging. X-rays may be used to assess the bones and joint, while an MRI can provide more detail when a ligament or meniscus injury is suspected.
Recovery time varies depending on the cause and the treatment required. Instability related to muscle weakness may improve progressively with rehabilitation, while recovery from a ligament injury or surgery can take considerably longer.
Yes, knee instability can recur in some cases. This may happen after a new injury or if the knee has not regained sufficient strength and control following treatment. The likelihood of recurrence also depends on the original cause and the treatment received.
MBBS (S’pore), MRCS (Edin), MMed (Ortho), FRCS (Ortho) (Edin)
With over 20 years of experience, Dr Wang Lushun is an orthopaedic surgeon who specialises in treating a wide range of sports injuries and musculoskeletal conditions. He has in-depth experience in minimally invasive surgery and advanced robotic surgery. Dr Wang provides orthopaedic care to athletes and everyday individuals throughout their journey to recovery.
