Knee swelling after an injury: what to do

Knee swelling after an injury can signal irritation, bleeding, or damage to a ligament, meniscus, or other tissue. It may appear quickly after a twist or impact, or build as the knee reacts. Swelling does not prove a specific tear, and a small injury can still limit movement.

A twisting injury followed by instability can occur with an ACL tear. Catching, clicking, or difficulty fully straightening the knee can occur with a meniscus tear. Pain at the front or side may involve a bursa, while a flare of knee osteoarthritis or gout can be triggered around the same time without a major impact. A Baker's cyst may become noticeable when joint fluid increases.

Tell the clinician how the injury happened, whether you heard a pop, how soon swelling appeared, and whether you can take steps. These details help decide whether examination, imaging, or another test is needed.

Stop the activity and protect the knee from further twisting or impact. Use comfortable rest, gentle positioning, and a wrapped cold pack for short periods if suitable for you. Elevation may reduce throbbing. Use support only if it has been recommended and does not cause numbness, colour change, or increased pain.

Avoid testing the knee repeatedly, forcing a stretch, or returning to sport because swelling briefly improves. Arrange an assessment if swelling persists, walking is difficult, the knee feels unstable, or movement remains restricted.

Seek urgent care if the knee looks deformed, becomes rapidly and severely swollen, cannot bear weight, is locked, or the foot becomes numb, pale, or cold. Fever with a hot swollen joint also needs prompt attention. These findings can indicate a serious injury, infection, or impaired circulation.

Ask which structure may have been injured, whether you need imaging, and what weight-bearing level is safe. Ask how to manage swelling, when physiotherapy may begin, and which symptoms would mean you should return urgently. Mention previous knee problems and medicines that may affect bleeding.