"Knee locking" is quite literally when your knee locks up momentarily, inhibiting your ability to move in any direction. This can also be described as "catching" where it feels as if your knee gets caught during extension or flexion, the knee "giving out," or as a popping sensation with knee movement. Unfortunately, there is no "key" or secret trick to unlock your knee joint, though various treatments exist to help with knee locking symptoms.

1. Knee Locking & Unlocking
"Knee locking" is quite literally when your knee locks up momentarily, inhibiting
your ability to move in any direction. This can also be described as "catching"
where it feels as if your knee gets caught during extension or flexion, the knee
"giving out," or as a popping sensation with knee movement. Unfortunately, there
is no "key" or secret trick to unlock your knee joint, though various treatments exist
to help with knee locking symptoms.
The human knee is a relatively complex joint, composed of numerous bones,
cartilage, tendons, and ligaments. The bones form the knee joint and the muscles
and tendons act around these bones to articulate the joint. The ligaments (such as
the anterior crucial element ligament or "ACL") exist to provide stability and make
sure the knee only moves in the way it is supposed to. Finally, the cartilage, here
known as the medial and lateral "meniscus," exists to provide shock absorption,
stabilization, and smooth movement of the knee joint.
Common characteristics of knee locking
It's likely that the following can describe your knee locking.
• A catching sensation with knee extension
• A feeling of knee instability
• Knee stiffness
• Pain with extension of the knee
• Difficulty walking, running, jumping, or using stairs
• Swelling of the affected knee
Knee Locking Causes
The knee is composed of bone, cartilage, tendons, and ligaments. Damage to any
of these structures can lead to knee locking and instability, though the culprit is
often the meniscus, the component made of cartilage. "True" knee locking, where
the ability to extend the knee is restricted for a few minutes, is generally caused by
damage to bones or cartilage that compose the knee itself. "Pseudo" knee locking,
where very brief locking is caused by temporary muscle spasm in response to
pain, is usually due to damage of surrounding structures.

2. Musculoskeletal causes
The following are different types of musculoskeletal causes that result in
knee locking.
• Wear and tear: Knee locking is often caused by years of wear and tear on
the joint, leading to accumulated damage to the bones and cartilage that
compose the knee.
• Cartilage damage: Damage to the cartilage of the knee, which provides
for smooth motion, can lead to catching and popping.
• Muscle and tendon damage: Overuse and strain of the muscles and
tendons that act on the knee can cause pain, which leads to difficult
movement and a sensation of catching.
• Ligament damage: Damage to the ligaments supporting the knee can
lead to instability and locking .
• Trauma: Trauma to the knee joint can result in free-floating bone
fragments which cause true locking of the knee. Here the movement is
restricted by the fragment, like putting a stick through the spokes of a
bicycle wheel. Trauma can also cause swelling, which may lead to knee
locking.
• Inflammation: Inflammation of the joint due to damage, autoimmune
disease, or infection can lead to knee locking.
9 Possible Knee Locking Conditions
Osteochondritis dissecans
Meniscal injury
Repeated kneecap dislocation (patellar subluxation)
Severe kneecap dislocation
Synovial chondromatosis
Pigmented villonodular synovitis
Knee arthritis
Rheumatoid arthritis
Psoriatic arthritis

3. Knee Locking Treatments and Relief
Knee locking can develop suddenly or over time due to damage to the
structures of the knee. Any sudden-onset and painful locking of the knee
should be evaluated by a physician due to the potential for irreparable
knee damage. Chronic or progressive-onset knee-locking can be
managed at home but may require physician evaluation if it interferes
with your quality of life or ability to walk.
At-home treatment
You can begin addressing your knee locking at home with the following
treatments.
• Rest: Avoiding activities that put stress of the knee, such as running or
jumping, and allow time for recovery. Exercises that include deep
bending of the knee should be avoided. With time, you can slowly
increase your exercise regimen to strengthen the muscles supporting the
knee.
• Stretching: Simple, at-home stretching of the muscles that support the
knee can strengthen them and stabilize the joint.
• Ice packs: Ice packs can be used to reduce the inflammation and swelling
associated with knee locking.
• Medications: Acetaminophen (Tylenol) or NSAIDS such as ibuprofen
(Advil, Motrin) can help reduce the discomfort and pain associated with
knee locking.
Prevention
Although not all knee injuries can be prevented — especially during
intense sporting events — there are certain precautions you can take to
prevent knee locking. Make sure to use proper form when exercising or
lifting heavy objects and consult a professional when necessary. If you
are training for a sport or marathon, be sure to allow periods of rest for
your joints and muscles. Be mindful of your overall health by drinking
plenty of water, getting seven to nine hours of sleep each night, and
eating a balanced diet.