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Knee Locking Symptoms, Causes & Common Questions

Understand your knee locking symptoms, including 9 causes & common questions.

Symptoms of knee locking

"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 [1]. 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.

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What causes of knee locking?

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.

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.

This list does not constitute medical advice and may not accurately represent what you have.

Osteochondritis dissecans

Osteochondritis dissecans, also called OCD, is a joint condition. It occurs when there is not enough blood flow within the end of a bone, under the protective cartilage. These bone layers begin to die and separate from the main bone, taking the cartilage with them.

The exact cause is not known. It may be due to overtraining a young person before the bone is entirely mature, which can interfere with blood supply.

Most susceptible are children and teenagers. The condition is found most often in only one joint, usually the ankle, knee, or elbow. However, any joint can be affected and there may be more than one.

Symptoms include swelling and pain in the joint during exercise, and sometimes "locking" of the joint. Osteochondritis dissecans may lead to osteoarthritis if not treated.

Diagnosis is made through patient history, physical examination, and imaging.

Treatment first involves rest because in children who are still growing, the bone and cartilage may heal spontaneously. If there are loose pieces of bone within a joint, surgery may be necessary.

Rarity: Rare

Top Symptoms: pain in one knee, knee stiffness, knee instability, knee pain that gets worse during a run, pop in the knee

Urgency: Primary care doctor

Meniscal injury

The menisci are the two pieces of cartilage serving as shock absorbers in the knee, between the lower end of the thighbone and the top of the shinbone. A torn meniscus is commonly referred to as "torn cartilage" in the knee.

Damage to a meniscus often happens along with another injury to the knee, especially when there is any forceful, twisting movement or a direct hit such as a tackle.

Older people may tear a meniscus through normal activity if the cartilage has become thin and worn due to aging.

Symptoms include pain, stiffness, and swelling. The knee will simply not work correctly and may catch, lock up, or give way.

Diagnosis is made through patient history, physical examination, simple motion tests, and imaging such as x-ray or MRI.

Depending on the exact form of the injury, the tear may be allowed to heal on its own with supportive care such as rest, ice, and nonsteroidal anti-inflammatory pain medication. In other cases, arthroscopic surgery followed by rehabilitation may be needed.

Rarity: Common

Top Symptoms: pain in one knee, knee stiffness, knee instability, pain in the inside of the knee, swollen knee

Urgency: Primary care doctor

Repeated kneecap dislocation (patellar subluxation)

Recurrent patellar subluxation is the continued instability of the kneecap, which causes anterior knee pain and usually occurs laterally. It occurs unpredictably with varying durations.

Rarity: Uncommon

Top Symptoms: pain in one knee, dull, achy knee pain, pain in the front of the knee, pain in the inside of the knee, swollen knee

Symptoms that always occur with repeated kneecap dislocation (patellar subluxation): kneecap dislocation

Urgency: Primary care doctor

Severe kneecap dislocation

The kneecap connects the muscles in the front of the thigh to the shinbone (tibia). When the kneecap slips out of the groove, problems and pain often result.

Rarity: Rare

Top Symptoms: constant knee pain, pain in one knee, knee pain from an injury, knee injury, kneecap dislocation

Symptoms that always occur with severe kneecap dislocation: knee pain from an injury, kneecap dislocation, constant knee pain

Urgency: Hospital emergency room

Synovial chondromatosis

Synovial chondromatosis is a disease affecting the synovium, which is a thin flexible membrane around a joint. It can often be confused with tendinitis and/or arthritis.

Rarity: Ultra rare

Top Symptoms: joint swelling, pain in one knee, pain in one hip, swollen knee, spontaneous knee pain

Symptoms that always occur with synovial chondromatosis: joint swelling

Symptoms that never occur with synovial chondromatosis: fever, night sweats, unintentional weight loss, warm red ankle swelling, warm red knee swelling, warm and red elbow swelling

Urgency: Primary care doctor

Pigmented villonodular synovitis

The synovium is a thin layer of tissue that surrounds joints, providing a small amount of fluid to lubricate the joint and aid in movement. In pigmented villonodular synovitis (PVNS), the synovium thickens and overgrows. This mass typically only affects one joint, is not cancerous, and does not spread to other parts of the body.

Rarity: Ultra rare

Top Symptoms: joint pain, pain in the outside of the hip, pain in one knee, groin pain, deep, throbbing hip pain

Symptoms that never occur with pigmented villonodular synovitis: knee instability

Urgency: Primary care doctor

Knee arthritis

Arthritis is inflammation of one or more of the joints. Pain, swelling, and stiffness are the primary symptoms of arthritis. Any joint in the body may be affected by the disease, but it is particularly common in the knee.

Rarity: Common

Top Symptoms: pain in both knees, knee stiffness, knee instability, swollen knee, morning joint stiffness

Symptoms that always occur with knee arthritis: pain in both knees

Urgency: Primary care doctor

Rheumatoid arthritis

Arthritis is a general term for multiple conditions that cause painful inflammation and stiffness throughout the body. Rheumatoid arthritis (RA) is a chronic condition that is autoimmune in nature, meaning that the body's immune system which normally protects the body by att...

Psoriatic arthritis

Psoriatic arthritis is a condition which causes inflammation of the joints. In most circumstances, psoriatic arthritis presents between the ages of 30 and 50 years and occurs after the manifestation of the symptoms of psoriasis, which is a disease of the skin. Psoriatic arthritis...

So... which condition is actually causing your knee locking?

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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.

When to see a doctor

If conservative measures or at-home treatments aren't enough, it's time to talk to your doctor. The following treatment options can be discussed with your physician.

  • Physical examination: Your physician will perform specific maneuvers with the affected knee to determine what is causing the knee locking.
  • Imaging: Imaging of the joint may be performed to pinpoint the cause of the knee locking.
  • Physical therapy: Professionally administered stretches and exercises can help strengthen and stabilize the knee.
  • Brace: Knee braces and immobilization may be used to reduce the forces to which the knee is exposed.
  • Medication: Certain medications which reduce inflammation can be used to help mitigate damage to the knee.
  • Surgery: Surgery can be performed for serious knee injury or long-lasting arthritis. These surgeries range from a simple repair of the knee cartilage to knee replacement for chronic and severe damage. True knee locking, as caused by bone or cartilage damage, will often require surgery for repair or to reduce symptoms.

When it is an emergency

You should seek help without delay if you have:

  • Extreme difficulty or inability to walk
  • Sudden-onset and severe knee pain and locking
  • Traumatic injury to the knee with resultant locking


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.

Questions your doctor may ask about knee locking

  • Do you feel like your knee is unstable, weak, or giving out?
  • Do you often feel your knees buckling?
  • Did you feel your knee cap pop out of place?
  • Did you just suffer from a high impact injury (e.g., a fall, collision, accident or sports trauma)?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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  1. Common knee injuries. American Academy of Orthopaedic Surgeons: OrthoInfo. Updated March 2014. OrthoInfo Link
  2. Torn meniscus. UW Medicine: Orthopaedics and Sports Medicine. UW Medicine Link
  3. Huri G, Biçer OS. Unusual cause of knee locking. Case Rep Orthop. 2013;2013:837140. NCBI Link
  4. Types of knee sprains, strains & tears. NYU Langone Health. NYU Langone Health Link
  5. Wilkerson R. Knee arthroscopy. American Academy of Orthopaedic Surgeons: OrthoInfo. Updated September 2016. OrthoInfo Link
  6. Gupte C, St Mart JP. The acute swollen knee: Diagnosis and management. J R Soc Med. 2013;106(7):259-268. NCBI Link