Why does my knee give out?
Last updated September 3, 2026.
Giving way means the knee's stabilizers are failing: an injured ligament or meniscus, or weak supporting muscles. The NHS says an unstable knee that gives way when you stand, will not straighten, or popped during an injury points to a torn ligament, tendon, or meniscus, and that a knee that locks, gives way, or painfully clicks should be checked. Without a single injury, an old sprain that never fully rehabbed, weak quads and hip muscles, or arthritis are the usual drivers. The practical danger is the fall when it buckles. Strength work is the main treatment for most causes, and a GP or physio can refer for a scan if the pattern suggests structural damage.
What to do
- Pause the triggering activity until the knee is assessed.
- Strengthen quads and hips: they are the knee's steering system.
- See a GP or physio for repeated giving way, swelling, locking, or incomplete straightening.
- Seek urgent care if you cannot bear weight, the knee has changed shape, or you have a fever with a hot, red knee.
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