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What is Knee Lock?

Pamela Pleasant
Pamela Pleasant

Knee lock refers to the problem that occurs when the knee cannot be straightened or bent. This locking most commonly happens when loose cartilage or a bone fragment has blocked or jammed the knee joint. A misalignment of the muscles or bones due to muscle strain or an injury also can cause this condition. In either situation, the knee can become stiff and frozen, which is accompanied by extreme pain. To treat knee lock, it is important to know what caused the initial symptoms.

Arthritis and natural aging can increase the risk for a knee lock. Over time, the cartilage that surrounds the bones in the knee can become worn out, causing it to begin to break off. The cartilage material can become lodged within the knee joint mechanism, making it impossible to bend the leg. If the cartilage is completely worn out, it is also possible for a chipped bone fragment to become jammed in the knee mechanism. This is referred to as an osteochondritis dissecans.

Intense exercise may cause knee lock.
Intense exercise may cause knee lock.

Intense exercise or a strain on the thigh muscles can cause a lock. Any weakness or tightness in the outer thigh muscles can affect the knee cap. The tightness causes a contraction of the muscle, which can result in a misalignment of the knee cap. It will remain stuck in this position until the muscle returns to normal. Even when the knee cap is aligned correctly, it can still take a considerable amount of time to gain the normal range of motion in the knee.

Misalignment of knee muscles due to an injury may cause knee lock.
Misalignment of knee muscles due to an injury may cause knee lock.

When a knee joint is injured or strained, there may be symptoms that are similar to a locked knee but it is not considered a true knee lock. A knee lock involves an inability to bend or move the knee, not just pain. A slight bump to the knee cap or running or jumping too hard can cause a knee lock sensation, which is called a pseudo- lock. Although the discomfort and pain can be real, the knee can still have a range of movement. The pseudo-lock typically goes away in a matter of days.

A diagram of the knee.
A diagram of the knee.

Anytime there is a restriction of movement in the knee, a medical evaluation should be done. If left unchecked, a bone fragment or loose cartilage can do permanent damage to the knee. Debris in the knee that causes a block may have to be removed surgically.

Discussion Comments


After my delivery, my left side knee gets locked. I can walk, but it's only hard going down stairs.


My brother's leg is locked due to brine stock. Is there any treatment for this to open the leg lock? Please help.


Sometimes knee lock is caused by torn meniscus, but another cause, often misdiagnosed, is a temporarily disjointed fibular head. The condition is called "Instability of the Proximal Tibeofibular Joint" and could account for the -majority- of true knee locks. The TFJ sits just under the meniscus, so is often mis-diagnosed. Look it up.

Unfortunately, there is no reliable surgical cure. We simply need to learn how to live with it.


@Istria- I have had knee surgery after having an injury that caused my knee to lock up, and I can tell you that the rehabilitation process usually takes anywhere from five months to nine months depending on the severity of the injury and your body's ability to heal. The first month of the rehabilitation process included a locking knee brace, crutches, and restricted movement only when there was no weight on the knee at all. After that, it is all up to your physical therapist and physician. Good luck.


@istria- I used to play soccer as a kid until I was severely injured by an illegal slide tackle. I took a cleat to my left knee and a body to my right knee, causing a severe hyperextension to my left knee and a twisted left knee. I had not stopped growing yet, so surgery was out of the question. The result is premature arthritis in my right knee, bursitis that flares up on the norm, tears on the ACL, MCL, and Meniscus on my left knee, and a slightly torn meniscus on my right knee. The injury happened when I was about ten years old, and I have been battling knee problems ever since.

About ten years ago, I tore the meniscus in my right knee again, this time severely enough for it to cause my knee to lock up in pain. I ended up having my knee scoped, and the torn cartilage fragments removed from the joint. I have the option for more extensive surgery, but I can't afford to be off my feet for the amount of time it takes for rehabilitation. Anyway, the rehabilitation process really depends on the type of injury, the treatment, and whether the problem is degenerative or the result of an injury.


What kind of injury can cause a knee to lock up? What type of knee rehabilitation is recommended for a knee that locks up?

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    • Intense exercise may cause knee lock.
      By: Monkey Business
      Intense exercise may cause knee lock.
    • Misalignment of knee muscles due to an injury may cause knee lock.
      By: Rido
      Misalignment of knee muscles due to an injury may cause knee lock.
    • A diagram of the knee.
      By: Alila
      A diagram of the knee.
    • Running too hard can cause a pseudo-lock.
      By: Dirima
      Running too hard can cause a pseudo-lock.
    • A misalignment of the muscles due to injury can cause knee lock.
      By: .shock
      A misalignment of the muscles due to injury can cause knee lock.