Mr Oni examining the knee of a female patient in a green top. No faces are visible in the image.

conditions

Knee Instability

A knee that feels as though it might give way, buckle, or let you down on stairs and uneven ground. Knee instability is unsettling, but it is very often caused by something treatable inside the joint rather than serious ligament damage. Mr Oni will find the cause and help you trust your knee again.

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What is knee instability?

Why a knee gives way: instability that is rarely a ligament problem

Knee instability is the feeling that the knee is unreliable, that it might suddenly give way, buckle, or fail to hold your weight, particularly on stairs, slopes or uneven ground. It can knock your confidence as much as it limits you physically.

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It is natural to assume this means a torn ligament, but in most patients, especially where there is some wear and tear, that is not the cause. Far more often it is a mechanical problem inside the joint, a meniscal tear that catches or shifts, arthritis leaving the surfaces uneven, or a loose fragment, or it is pseudo-instability, where pain or swelling briefly switches off the muscles so the knee feels as though it gives way without actually being loose.

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This matters, because these causes are usually very treatable, and rarely need the kind of major ligament reconstruction people often fear. Once Mr Oni has identified exactly why the knee feels unstable, most patients can rebuild their stability and their confidence.

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Mr Oni focuses on meniscal injuries, cartilage damage, arthritis and mechanical knee problems. He does not routinely carry out acute ligament reconstruction, such as ACL surgery, but he is happy to assess complex knee symptoms, particularly where a meniscal problem or early arthritis is suspected, and to advise on the right next steps.

knee with sports tape across the kneecap

Recognising the condition

Common symptoms of knee instability

The main sign of knee instability is the knee giving way or feeling as though it might, often when going downstairs, turning, or walking on uneven ground. Many people also notice catching, a sense that the knee shifts or slips, swelling after activity, and a growing wariness of movements they no longer trust. These are the signs and symptoms patients most commonly notice.

The knee giving way

A sudden sense that the knee is buckling or about to give out, especially on stairs or uneven ground.

Feeling the knee shift or slip

A sensation that the joint moves, slips or is not tracking properly as you walk or turn.

Catching or locking

The knee catching or briefly locking, which can trigger an episode of giving way.

Difficulty on stairs and slopes

Hesitation or a loss of control going down stairs, on slopes, or across uneven ground.

Swelling after activity

The knee swelling, often after the activity that triggered an unstable episode.

Sharp pain during movement

A sudden sharp pain as the knee gives way or twists, often settling afterwards.

Weakness in the knee

A feeling that the knee is weak or cannot be relied on to hold your weight.

Loss of confidence

Avoiding certain movements or activities because you no longer trust the knee.

The feeling of a knee giving way can come from several things, most often a meniscal tear or arthritis affecting how the joint moves, and less commonly a ligament problem. It can also overlap with a knee that locks, which is a related but distinct issue. Because the treatment depends on the cause, an accurate diagnosis matters, and Mr Oni will pinpoint it, usually with an examination and a scan, at your first appointment.

Knee instability usually comes from one of two things. Either there is a genuine mechanical problem inside the joint that interferes with smooth movement, or there is pseudo-instability, where pain or swelling briefly shuts down the muscles that control the knee, so it feels as though it gives way even though it is not actually loose.

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The most common mechanical causes are a meniscal tear, where torn cartilage catches or shifts, and arthritis, where worn, uneven surfaces and the occasional loose fragment disturb the way the knee moves. Weakness or wasting of the thigh muscles, often after a period of pain or reduced activity, adds to the problem by leaving the knee less well supported.

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Ligament injuries can cause true instability too, but in patients with wear and tear this is a less common cause than people expect. Identifying which of these is responsible is the key to treating it, because the right approach is quite different for each.

Meniscal tear

Torn cartilage that catches or shifts inside the knee, one of the most common reasons a knee gives way.

Arthritis

Worn, uneven joint surfaces and loose fragments that disturb smooth movement, often with muscle weakness alongside.

Pseudo-instability

The knee feels unstable but is not loose. Pain or swelling briefly switches off the supporting muscles, so it seems to give way.

causes and types

What causes knee instability?

Mr oni is the main focus of the image with him looking down and pointing at the model knee in his hand.

how mr oni Helps

diagnosis & Next Steps

Getting the diagnosis right comes first, and with an unstable knee the key is finding why it gives way. Mr Oni will ask exactly when and how it happens and examine the knee, checking its movement, muscle control and the ligaments, then arrange imaging where needed, an MRI shows a meniscal tear or cartilage damage, while an X-ray reveals arthritis. That way the treatment targets the real cause rather than just the symptom.

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consultation

A thorough consultation reviewing your symptoms, movement, and any existing imaging. No assumptions, no rushed conclusions.

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clinical examination

A hands-on assessment of the joint - checking movement, strength and what triggers your pain - to understand exactly what's going on.

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imaging

Where needed, an X-ray or scan to confirm the diagnosis and see the joint clearly, so nothing is left to guesswork.

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treatment plan

Every option considered. From load management and physiotherapy to further investigations and surgical options. A plan built around your lifestyle and goals, not a one-size-fits-all protocol.

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with the right treatment

life after treatment

Confidence in your knee again

The knee stops feeling as though it might let you down, so you can move and turn without second-guessing it.

Steady on stairs and uneven ground

Stairs, slopes and uneven ground stop being something to approach with caution.

Back to activity and sport

Walking, exercise and the activities you enjoy become possible again as the knee feels dependable.

Fewer episodes of giving way

The sudden buckling and giving-way episodes settle as the underlying cause is treated.

Recognising the condition

How knee instability is treated

How knee instability is treated depends on what is causing it. Strengthening the muscles around the knee through physiotherapy is the foundation for almost everyone, and for many it is enough on its own. Where a meniscal tear is catching the joint, a short keyhole operation, knee arthroscopy, can settle it. Where arthritis is the cause, the options are the same as for knee arthritis, ranging from injections through to a partial or total knee replacement when it is advanced. Mr Oni will recommend the right approach once he knows the cause.

related treatments

Knee Arthroscopy

Keyhole knee surgery to diagnose and treat mechanical problems such as a torn meniscus, a loose fragment, or a knee that locks or catches.

Knee Arthroscopy
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a close up image of surgeons hands holding knee arthroscopy equipment. the handles and probes are visible only.

related treatments

Arthrosamid Injection

A non-surgical injectable treatment for knee osteoarthritis that can provide lasting relief from joint pain.

Arthrosamid Injection
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Hands blue glove with black sleeves, holding an arthrosamid injection needle in both hands.
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Patient Stories

Hear from patients who have undergone investigations and treatments for their hip and knee problems with Mr Oni.

★ ★ ★ ★ ★

Mr Richard M.

Mr Oni explained everything clearly and the whole process was faultless. I was walking the corridors within two days and driving again in a fortnight. The scar is so neat you can hardly see it.

Treatment

Hip Replacement

★ ★ ★ ★ ★

Mr Robert F.

Mr Oni and the team were very professional throughout. The recovery was tough, but I stuck to the exercises and only needed over-the-counter painkillers. Two months on, I completed a nine-mile bike ride.

Treatment

Robotic Knee Replacement

★ ★ ★ ★ ★

Ms Liz.

Mr Oni and Libby are a really good team and made me feel completely comfortable. I'd been limping for a year, but almost marched into my follow-up. I've got my life back.

Treatment

Arthrosamid Injection

★ ★ ★ ★ ★

Mr Tony G.

Mr Oni gave me real confidence going into surgery, and I cannot fault my experience. I'm back to walking the dogs, gardening and farm work. The steep hills that once bothered me, now I don't even notice.

Treatment

Robotic Knee Replacement

★ ★ ★ ★ ★

Ms Zoe G.

Mr Oni and the team were incredibly supportive, kind and patient. I was walking with a frame the same day and dressing myself the next morning. Within two weeks I could pick my daughter up from school.

Treatment

Hip Replacement

★ ★ ★ ★ ★

Mr Ian F.

Mr Oni recommended the Arthrosamid injection and everything has been brilliant. Two weeks later I was rotovating the garden for two hours. It felt like some sort of miracle, I didn't notice I'd had bad knees.

Treatment

Arthrosamid Injection

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Take the next step

Book a consultation about your unstable knee

If your knee keeps giving way or feels unreliable, Mr Oni will work out exactly why, examine it, arrange a scan if needed, and explain what is going on. From there he will talk you through a clear plan, often physiotherapy, sometimes a keyhole procedure or treatment for arthritis, depending on the cause. No pressure, no assumptions.

Book your Consultation
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locations

Mr Oni consults and operates at several leading private hospitals across the region, so you can choose the location most convenient for you.

Exterior Image of The Horder Centre Crowborough East Sussex

The Horder Centre

St John's Road
Crowborough
East Sussex
TN6 1XP

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Exterior Image of the Nuffield Health Private Hospital in Tunbridge Wells

Nuffield Health

Kingswood Road
Tunbridge Wells
Kent
TN2 4UL

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Exterior Image of the Vale Health Clinic in Tunbridge Wells, Kent

Vale Health Clinic

31-33 Vale Road
Tunbridge Wells
Kent
TN1 1BS

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Frequently asked questions

A knee that keeps giving way usually has a mechanical cause inside the joint, most often a meniscal tear or arthritis, or it is pseudo-instability, where pain briefly weakens the muscles that steady the knee. A ligament problem is possible but less common in this situation. Because the cause guides the treatment, repeated giving way is worth having assessed.

Yes, and it commonly does. In most patients the knee feels unstable because of a meniscal tear, arthritis, or weakness in the muscles that support it, rather than a torn ligament. This is good news, as these causes are usually very treatable without major ligament surgery.

Pseudo-instability is when the knee feels as though it might give way but is not actually loose. Pain, swelling or joint irritation briefly switches off the muscles that control the knee, creating a sensation of weakness or buckling. It often improves as the underlying cause, such as arthritis, is treated.

Yes. Arthritis can make a knee feel unstable through a mix of pain, muscle weakness and uneven, worn joint surfaces, particularly on stairs and when walking. When arthritis is the cause, it is treated the same way as knee arthritis generally, from physiotherapy and injections through to a knee replacement if it is advanced.

Often not. For most people, strengthening the muscles around the knee with physiotherapy is the foundation and frequently enough. Surgery is reserved for specific causes, such as a keyhole procedure for a meniscal tear, while arthritis-related instability is treated on its own pathway. Mr Oni will only recommend surgery when it is genuinely the best option.

Yes, very often. Targeted strengthening of the thigh and hip muscles improves the support around the knee and is one of the most effective treatments for instability. A physiotherapist can tailor a programme so you build stability safely.

Answers written by Mr Tofunmi Oni, Consultant Orthopaedic Surgeon (MBChB BSc PGDip FRCS (Tr & Orth), GMC 7074916). Mr Oni does not perform ligament reconstruction and refers patients who need it to a specialist ligament surgeon. Figures come from the NHS, Cochrane and the studies listed in the sources at the end. Last reviewed October 2026.

Why does my knee give way or buckle?

Buckling is common: about 12% of adults in a population study reported at least one episode in the previous three months, and it was strongly linked to knee pain and weak thigh muscles rather than only to ligament damage. Other causes are arthritis, a meniscal tear catching, kneecap instability and, less commonly, a ligament injury. In adults over 40 most giving way happens without any ligament tear.

Is knee buckling serious?

It matters mainly because of falls: in that study about one in eight buckling episodes ended in a fall, and people who buckle regularly are 1.6 to 2.5 times more likely to have recurrent falls. Buckling that keeps happening, or that follows an injury, should be assessed. The NHS advises contacting 111 if the knee gives way, locks or painfully clicks.

Why does my knee feel like it is about to give way?

That sense of apprehension without an actual collapse usually comes from pain inhibition, where the brain switches off the thigh muscle briefly in response to pain, or from a kneecap that is tracking poorly. It is also typical of early arthritis. A knee that feels as though it will go, but never does, is usually a muscle and confidence problem rather than a structural one, and responds well to strengthening.

Can knee instability happen without a ligament injury?

Yes, and in older adults that is the usual pattern. Pain inhibition and weak quadriceps let the knee give under load, and arthritis, meniscal tears and kneecap maltracking are the common culprits. Ligament laxity produces a different pattern, giving way with twisting or pivoting, usually after a clear injury, and is assessed separately. If a ligament reconstruction is needed I refer to a specialist ligament surgeon.

Can arthritis cause a knee to give way?

Yes. Buckling was reported in 14% of painful knees compared with 2% of pain free knees in the population study, and it is particularly common in people with knee osteoarthritis, where pain and muscle weakness combine. Treating the arthritis and strengthening the thigh reduces it.

What is pseudo instability of the knee?

A knee that gives way because of pain or weakness rather than because a ligament is lax. On examination the ligaments are intact, but the quadriceps are weak or inhibited and the knee collapses under load. It is the commonest form of instability in adults over 40 and is treated with rehabilitation, not surgery.

What is the best treatment for a buckling knee?

Treatment targets the cause: quadriceps and hip strengthening with balance training for weakness and arthritis, treatment of a meniscal tear or kneecap problem where present, and pain control. For most people that is a physiotherapy programme over several weeks rather than an operation.

Is a knee brace good for a buckling knee?

A brace can give a sense of security, but a Cochrane review found low quality evidence that knee braces make little or no difference to pain or function in osteoarthritis at twelve months, and NICE says not to offer braces or supports routinely unless there is instability or abnormal loading. A brace is an adjunct while you build strength, not a fix.

Can exercises improve knee instability?

Yes, for most people. Strengthening the quadriceps and hip muscles and improving balance reduces giving way caused by weakness, pain and arthritis, and NICE recommends exercise as core treatment for osteoarthritis. The programme needs to be progressive and continued for months rather than weeks.

Will I need surgery for knee instability?

Usually not. Surgery is reserved for a mechanical cause, meaning a displaced meniscal tear, a loose body or an unstable kneecap, or for a ligament rupture that keeps giving way despite rehabilitation. Ligament reconstruction is done by a surgeon who specialises in it, and I refer those patients on.

Sources

Felson DT et al. Knee buckling: prevalence, risk factors, and associated limitations in function. Ann Intern Med 2007;147:534-40.

Nevitt MC et al. Symptoms of knee instability as risk factors for recurrent falls. Arthritis Care Res 2016;68:1089-96.

Duivenvoorden T et al. Braces and orthoses for treating osteoarthritis of the knee. Cochrane Database of Systematic Reviews 2015, CD004020.

NICE NG226, Osteoarthritis in over 16s (October 2022), recommendations 1.3.1 and 1.3.11. https://www.nice.org.uk/guidance/ng226

NHS.uk, Knee pain (reviewed December 2023). https://www.nhs.uk/conditions/knee-pain/

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get in touch

Book your initial
consultation

See Mr Oni at The Horder Centre, The Nuffield Hospital or The Vale Health Clinic.

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Email: libby.gibbs@horder.co.uk

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