Answers written by Mr Tofunmi Oni, Consultant Orthopaedic Surgeon (MBChB BSc PGDip FRCS (Tr & Orth), GMC 7074916). Figures come from NICE, the NHS, the British Association for Surgery of the Knee and the sources listed at the end. Last reviewed October 2026.
Why does my knee lock, and what does locking feel like?
True locking is a mechanical block: the knee gets stuck, usually a little short of straight, and cannot be forced straight however hard you try. The commonest cause is a displaced bucket handle tear of the meniscus, and loose fragments of cartilage or bone can also jam the joint. Pseudo locking is a temporary catch from pain or muscle spasm, often from arthritis or a kneecap problem, and releases with time or painkillers. The distinction matters because the treatment is different.
How do I unlock a locked knee?
Do not force it. Rest, ice and painkillers may release a pseudo lock from spasm, and gently moving the knee in and out of a comfortable range sometimes lets a catch settle. A true mechanical lock rarely unlocks reliably and needs assessment. Self manoeuvres to wrench the knee straight are not advised, because they can displace the tear further.
Can I walk on a locked knee?
You can usually bear some weight with the knee slightly bent, with crutches if needed, but prolonged walking on a locked knee is not advised. If it will not straighten, seek urgent assessment through your GP, 111 or an urgent treatment centre.
Is a locked knee an emergency?
A truly locked knee needs prompt specialist assessment, usually within days, so that a displaced tear can be repaired while it is still repairable; repairs done within six weeks succeed about 83% of the time, against 52% when done late. Some specialists describe it as an orthopaedic emergency, though it is not usually an A&E emergency unless the knee is deformed, numb, or hot and swollen with fever. The NHS advises 111 if the knee locks and A&E if it has changed shape or you have lost feeling.
Will knee locking go away on its own?
Pseudo locking often settles as the underlying pain or spasm improves. True locking from a displaced tear or loose body generally does not, because the fragment stays where it is.
Is knee locking a symptom of arthritis?
Arthritis more often causes stiffness, catching and pseudo locking than a true mechanical lock. Stiffness after sitting, gelling in the morning and the knee giving way are not the same thing as mechanical locking. A true block to straightening in an arthritic knee can come from a loose body or a displaced degenerative tear, which is the one situation where keyhole surgery still has a role in an arthritic knee. NICE otherwise advises against arthroscopic washout for osteoarthritis.
Does a locking knee always need surgery, and can it be cured?
No. Pseudo locking is treated with physiotherapy, pain control and treatment of the underlying arthritis or kneecap problem. True mechanical locking from a displaced tear or loose body usually does need keyhole surgery, which is effective at removing the block; repairing the tear where possible gives the best long term result and is more likely to succeed if done early. Loose bodies are removed at the same procedure.
What is the difference between a knee locking and a knee giving way?
Locking is the knee getting stuck and refusing to straighten. Giving way is the knee buckling or collapsing under load. They have different causes: locking points to something physically jammed in the joint, while giving way is more often weak thigh muscles, pain inhibition, arthritis or a kneecap problem, and only sometimes a ligament injury. Both deserve assessment, but giving way is rarely urgent.
What tests will I need for a locking knee?
Examination of the knee first, then an MRI if a meniscal tear or loose body is suspected, because MRI is sensitive for the displaced tears that cause true locking, though a static scan can occasionally miss a tear that only displaces with movement. An X ray is useful for loose bodies and for assessing the degree of arthritis, which affects what surgery is sensible.
Sources
Rhind J et al. The locked knee. Br J Hosp Med 2024.
Abram SGF, Beard DJ, Price AJ, BASK Meniscal Working Group. Arthroscopic meniscal surgery: a national society treatment guideline and consensus statement. Bone Joint J 2019;101-B:652-9.
NICE NG226, Osteoarthritis in over 16s (October 2022), recommendation 1.7.1. https://www.nice.org.uk/guidance/ng226
NHS.uk, Knee pain (reviewed December 2023) and Meniscus tear (reviewed September 2026). https://www.nhs.uk/conditions/knee-pain/
Felson DT et al. Knee buckling: prevalence, risk factors, and associated limitations in function. Ann Intern Med 2007;147:534-40.
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