Patient question
I can't straighten my knee all the way. What could it be?
Dr. Pablo GelberOrthopaedic Knee Surgeon
Quick answer
A knee that will not go fully straight is usually held by swelling, a torn meniscus or loose fragment blocking the joint, scar tissue after surgery, or arthritis. Even a few degrees matters for walking, so it is worth assessing early, advises Dr. Pablo Gelber, knee surgeon at Aman Hospital in Doha.
Why full straightening matters
When you stand, a fully straight knee locks so the bones carry your weight with little muscle effort. If the knee stays even slightly bent, the quadriceps has to work constantly, the kneecap is pressed harder and you tend to limp. Over months, the back of the knee tightens and the loss becomes harder to reverse.
Compare both legs lying flat: if you cannot press the back of one knee down to the bed as far as the other, that is a loss of extension.
Likely causes
- Swelling, which holds the knee in a slightly bent position because that is where the joint has most room
- A meniscus tear, especially a bucket-handle tear, that has flipped into the front of the joint and blocks it
- A loose fragment of cartilage or bone
- After ACL reconstruction, a nodule of scar tissue at the front of the graft (sometimes called a cyclops lesion)
- Arthritis with bone spurs and a tight joint capsule
- Tight hamstrings and calf muscles after injury or prolonged sitting
What you can try
If there is no sudden locking, reduce swelling with ice and elevation, then do gentle straightening exercises several times a day. Lie on your back with a rolled towel under the heel, not under the knee, and let gravity straighten it for a few minutes. Tighten the thigh muscle to press the knee down.
Avoid sleeping with a pillow under the knee; it feels comfortable but keeps the knee bent for hours.
When to see a knee surgeon in Doha
Seek urgent assessment if the knee suddenly locked and will not straighten after a twist, because a trapped meniscus is easier to repair early. Seek urgent care for a hot, red, swollen knee with fever.
Book a review if the loss is gradual or has not improved after a couple of weeks of exercises, or if your knee is not reaching full straightening after surgery. At Aman Hospital, Dr. Gelber examines the knee and usually arranges an MRI to look for a mechanical block, which can often be treated with keyhole surgery.
Frequently asked questions
Is it normal not to straighten fully right after ACL surgery?
Some loss in the first days is common, but regaining full straightening is one of the earliest goals. Tell your surgeon if it is not returning within the first few weeks.
Can physiotherapy fix a knee that will not straighten?
Often, when swelling or tight muscles are the cause. A mechanical block such as a flipped meniscus usually needs surgery to remove or repair it.
Why does my knee feel springy when I try to straighten it?
A springy, rubbery stop rather than a firm one often suggests something is trapped inside the joint, such as a torn meniscus. That deserves an examination.
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