Patella: Kneecap Anatomy, Function, Injuries and Care

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick Answer: What is the patella?

The patella is the kneecap, a small oval-shaped bone at the front of the knee and the largest sesamoid bone, meaning it is embedded in a tendon. It works with the quadriceps to straighten the leg, protects the knee joint and connects with nearby tendons and ligaments. New knee symptoms or injuries should be evaluated by a healthcare professional.

What the research says

• Recurrent dislocation is common, and the evidence on surgery versus non-surgical care is still uncertain. A Cochrane review notes that recurrent dislocation occurs in up to 40% of people after a first kneecap dislocation. The review included 10 studies (519 participants). After a first dislocation, pooled data from 8 studies (438 participants) suggested 157 fewer recurrent dislocations per 1,000 people with surgery over two to nine years (95% CI 209 fewer to 87 fewer), but the authors rated the certainty of the evidence as very low and could not say whether surgery improves function (Smith et al., Cochrane Database Syst Rev, 2023). [2]

• Rehabilitation after a dislocation can take several forms. In a systematic review of seven randomized trials (282 patients), an unstructured lower-limb physical therapy program gave outcomes similar to specific exercises. Surgery was associated with fewer re-dislocations, but whether it produces better function than conservative care remains unclear. A limited-range-of-motion brace, stretching and neuromuscular exercises were the most commonly recommended approaches (Flores et al., J Orthop Surg Res, 2023). [3]

• For patellofemoral pain, exercise therapy plus education comes first. A best-practice guide synthesizing 65 high-quality randomized trials (3,796 participants) with patient and expert input recommends knee-targeted exercise therapy, with or without hip-targeted exercise, underpinned by education. Supporting options such as foot orthoses, manual therapy, movement retraining or taping are tailored to the individual (Neal et al., Br J Sports Med, 2024). [4]

What is the patella?

The patella, commonly called the kneecap, is the bone at the front of the knee joint. It is the largest bone in the body embedded in a tendon, which makes it a sesamoid bone.

The patella is more than a cover over the knee. It works with the quadriceps muscle to help move the leg, protects the knee joint and supports the network of muscles, tendons and ligaments around the joint.

Trauma that hurts the knee is the most common cause of patellar injury. Dislocations and fractures can affect how the knee moves and may require treatment, rehabilitation or, in some cases, surgery.

What does the patella do?

The patella has two main jobs: helping the quadriceps straighten the leg and protecting the knee joint.

Patella function	Why it matters
Helps extend the leg	The patella works with the quadriceps muscle and tendon to straighten the knee.
Protects the knee	Its position at the front of the joint helps shield structures behind it.
Supports the movement system	It connects with the quadriceps tendon above and patellar ligament below while working with nearby muscles and ligaments.

The patella is part of a coordinated movement system. Pain or damage in the kneecap, its surrounding tissues or the joint surface can affect walking, stairs, squatting and other movements.

Where is the patella located?

The patella sits at the front of the knee and covers the knee joint. It forms a bridge between the quadriceps muscle and the lower leg.

Its top, or base, connects to the quadriceps muscle through the quadriceps tendon. Its bottom, or apex, connects to the tibia through the patellar ligament.

The patella’s inner and outer surfaces move against corresponding areas of the femur. Healthcare professionals may use terms such as medial facet, lateral facet and femoral condyle to describe the location of pain or damage.

What does the patella look like?

The patella is generally oval-shaped with a slight point at the bottom. Most adult patellae, the plural of patella, are around 1.75 inches long and 1.5 inches wide.

Structure	Connection or relationship
Base of patella	Connected to the quadriceps muscle by the quadriceps tendon.
Apex of patella	Connected to the tibia by the patellar ligament.
Medial facet	The inner side that moves with the femur’s medial condyle.
Lateral facet	The outer side that moves with the femur’s lateral condyle.
Patellar surface	The front-of-knee bone that protects the joint and supports extension.

These labels are mainly useful in clinical settings. A clinician may use them to describe where a fracture or pain is located.

What common conditions affect the patella (kneecap)?

Many causes of knee pain involve the patella or the tissues around it. Examples include patellofemoral pain syndrome, patellar dislocation, patellar instability, patella fracture and patellar tendinitis.

Condition	General description
Patellofemoral pain syndrome	Pain involving the joint between the patella and femur, often described as anterior knee pain.
Patellar dislocation	The kneecap moves completely out of its normal position.
Patellar instability	The kneecap does not track or remain stable normally in its groove.
Patella fracture	A break in the kneecap, often following trauma.
Patellar tendinitis	Inflammation or irritation involving the patellar tendon or ligament area.
Patellar subluxation	A partial dislocation in which the kneecap moves partly out of position.

A symptom or sound does not establish which condition is present. Professional evaluation is needed when knee symptoms are new, persistent or interfere with walking or movement.

How is a patella (kneecap) dislocation different from a subluxation?

A dislocation means the kneecap has moved completely out of its normal position. A subluxation is a partial dislocation: the kneecap may move partly out of place but still remain in its groove.

With a patellar subluxation, a person may still be able to walk, but the knee can feel uncomfortable or unsteady. A popping sound may occur as the kneecap moves.

Injuries or a joint that is too loose can contribute to patellar subluxation. A clinician can distinguish subluxation from dislocation and from other causes of knee pain through the history, physical examination and, when needed, imaging.

How does osteoporosis affect the patella?

Osteoporosis weakens bones and can make them more susceptible to sudden, unexpected fractures. It can affect any bone, including the patella. [1]

Many people do not know they have osteoporosis until a fracture occurs because there are often no obvious symptoms beforehand. Women and adults older than 50 have an increased risk of developing osteoporosis. [1]

A healthcare professional may recommend a bone-density test to identify osteoporosis before a fracture. Bone-health decisions depend on age, medical history, medications, family history and other risk factors.

How is the patella evaluated?

The most common test performed directly on the patella is the patellar reflex test. During the test, a clinician taps the knee just below the kneecap with a reflex hammer. The stimulation triggers an involuntary reflex that should make the leg extend.

The patellar reflex may be part of a routine examination or a nervous-system evaluation. It does not by itself diagnose a patellar injury or explain every type of knee pain.

When a person has experienced a patellar injury or fracture, imaging may be needed.

Test	What it may help show
X-ray	Bone alignment, fracture or other visible changes.
MRI	Detailed views of soft tissues and bone-related structures.
CT scan	Detailed cross-sectional images, including complex fracture patterns.
Physical examination	Stability, movement, tenderness and the way symptoms change with activity.

The appropriate combination of tests depends on the injury, symptoms and clinical question.

How are patellar conditions treated?

The patella usually does not need treatment unless an injury, fracture, instability problem or knee-pain condition affects it.

Common treatment approaches may include wearing a brace or other immobilizing device, resting or avoiding the activity that caused the injury, physical therapy, ice and over-the-counter pain relievers. A healthcare professional can explain which options are appropriate and how long recovery may take.

Patella fracture treatment

Treatment for a patella fracture depends on the fracture type and what caused it. Immobilization with a splint or cast may be needed. Some fractures require surgery to realign the bone and secure it while it heals.

Recovery time varies. A treating clinician or surgeon can explain what to expect for a specific fracture.

Osteoporosis treatment

Osteoporosis care may include exercise, vitamin and mineral supplements and prescription medication. The right plan depends on bone density, fracture risk, overall health and other factors. [1]

Exercise and supplements are not automatically appropriate as the only treatment for everyone. A healthcare professional can create an individualized bone-health plan.

When should knee symptoms be evaluated?

Arrange professional evaluation for new knee symptoms, trouble walking or difficulty moving the knee. Evaluation is particularly important after a direct blow, fall, twisting injury or other trauma.

A clinician can assess whether symptoms involve the patella, surrounding tendons and ligaments, the femur or tibia, the knee joint or another structure.

Do not try to force a kneecap back into place or rely on a sound such as popping to determine the diagnosis. Professional care can help guide safe next steps.

How can you support patella and bone health?

Healthy habits can support bone strength, mobility and injury prevention, although they cannot prevent every condition.

Protective habit	How it may help
Follow a balanced diet and activity plan	Supports general and bone health.
Ask about bone-density testing	May identify osteoporosis before a fracture, especially when risk is higher.
Wear a seat belt	Helps reduce injury risk during vehicle crashes.
Use activity-appropriate protective equipment	Helps protect the knee during sports and other activities.
Reduce trip hazards	A safer home and workspace may lower fall risk.
Use proper tools	Avoid standing on chairs, tables or countertops to reach items.
Use a cane or walker when needed	Can support safer walking when balance or fall risk is a concern.

A healthcare professional can help match exercise, mobility aids and bone-health strategies to your abilities and risks.

What questions should you ask a healthcare professional about the patella?

Questions to ask about patella problems cover whether the kneecap is involved, which imaging you need, treatment options such as a brace or surgery, and safe activities while healing.

• Could my symptoms involve the patella or another knee structure?

• Do I need an X-ray, MRI or CT scan?

• Is my kneecap stable, partially displaced or fully dislocated?

• Would a brace, activity modification or physical therapy help?

• If I have a fracture, will I need a cast, splint or surgery?

• Should I discuss osteoporosis or a bone-density test?

• What activities are safe while the knee heals?

• What signs should prompt follow-up?

Conclusion

The patella is a small but important bone at the front of the knee. It works with the quadriceps to straighten the leg, protects the knee joint and connects with the tendons, ligaments and bones that support movement.

Trauma, patellofemoral pain, instability, dislocation, subluxation, fracture, tendinitis and osteoporosis can all affect the kneecap or the structures around it. Because similar symptoms can come from different causes, evaluation should focus on the injury pattern, examination and any needed imaging.

Frequently Asked Questions

What is the patella?

The patella is the kneecap, an oval-shaped bone at the front of the knee joint. It is the largest sesamoid bone, meaning it is embedded in a tendon.

What does the patella do?

The patella works with the quadriceps to help straighten the leg and protects the knee joint. It also supports nearby muscles, tendons and ligaments.

What connects to the patella?

The quadriceps tendon connects the top of the patella to the quadriceps muscle. The patellar ligament connects the bottom of the patella to the tibia, or shin bone.

What is a patellar subluxation?

A patellar subluxation is a partial dislocation. The kneecap may move partly out of position but still remain in its groove. It can cause discomfort, unsteadiness or a popping sound.

What is the difference between a patellar dislocation and subluxation?

A dislocation means the kneecap moves completely out of position. A subluxation means it moves partly out of position and may still remain in its groove.

Can osteoporosis affect the patella?

Yes. Osteoporosis weakens bones and can make the patella more likely to fracture. A clinician may recommend a bone-density test when risk is elevated.

How is the patella tested?

A clinician may check the patellar reflex by tapping below the kneecap with a reflex hammer. After injury or fracture, X-rays, MRI or CT may be used.

Does every patella injury need surgery?

No. Care depends on the injury. Some problems may be managed with rest, a brace, physical therapy, ice or pain relievers. Some fractures or dislocations may require surgery.

When should I seek care for knee symptoms?

Arrange evaluation for new symptoms, trouble walking or difficulty moving the knee, especially after trauma. Do not try to force a kneecap back into place yourself.

How can I protect my patella?

Use seat belts and appropriate protective equipment, reduce fall hazards, use proper tools, follow a bone-health plan and use a cane or walker when recommended for safer walking.

Related Reading

Patellar Grind Test (Clarke's Sign): Checking Kneecap Pain explains the knee exam that checks for cartilage problems under the kneecap.

References

1. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Osteoporosis. National Institutes of Health. Last reviewed December 2022. https://www.niams.nih.gov/health-topics/osteoporosis

2. Smith TO, Gaukroger A, Metcalfe A, et al. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database Syst Rev. 2023;1(1):CD008106. PMID 36692346. https://doi.org/10.1002/14651858.CD008106.pub4

3. Flores GW, de Oliveira DF, Ramos APS, et al. Conservative management following patellar dislocation: a level I systematic review. J Orthop Surg Res. 2023;18(1):393. PMID 37254200. https://doi.org/10.1186/s13018-023-03867-6

4. Neal BS, Lack SD, Bartholomew C, et al. Best practice guide for patellofemoral pain based on synthesis of a systematic review, the patient voice and expert clinical reasoning. Br J Sports Med. 2024;58(24):1486-1495. PMID 39401870. https://doi.org/10.1136/bjsports-2024-108110

Disclaimer

This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.

This article explains patellar anatomy, function, common conditions, evaluation and general care pathways. It does not diagnose knee pain, determine whether a kneecap is dislocated or subluxed, recommend a personal treatment plan or replace professional care.