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🦵 Lower limb

🦵Knee

The knee is the body's largest joint and one of its most frequently injured, relying on ligaments and surrounding muscles rather than bony shape for stability.

Also called: Tibiofemoral Joint · Patellofemoral Joint

OverviewAnatomyConditionsAssessmentExercisesProgressionPrecautionsRecovery

Reviewed 2026-08·Sources & research·Media credits

Illustration of the knee joint showing bones, ligaments, and menisci
Genusfotografen (Tomas Gunnarsson) / Wikimedia Sverige · CC BY-SA 4.0

Quick facts

Modified hinge (tibiofemoral + patellofemoral)Joint type
Flexion, extension, slight rotationPrimary motions
Overuse, ligament sprain, meniscus injury, osteoarthritisCommon cause
6–12 weeks for most soft-tissue injuriesTypical recovery
ACL, menisci, quadriceps tendonKey structures
Locked knee or inability to bear weightRed-flag signs

The knee is the largest and one of the most heavily loaded joints in the body, connecting the thigh bone to the shin bone while the kneecap glides in a groove at the front to assist with leg extension. Unlike the hip, the knee's bony surfaces are relatively flat, so stability depends heavily on a set of internal and surrounding ligaments.

Because the knee bears substantial load during walking, running, jumping, and pivoting, it is among the most frequently injured joints in sport and one of the most common sites of age-related osteoarthritis. Conditions range from overuse-related tendon and cartilage irritation to acute ligament and meniscus injuries.

This page reviews the knee's anatomy, common conditions across age groups and activity levels, how clinicians assess it, and general exercise and recovery patterns used in both non-surgical and post-surgical rehabilitation.

The profile

655560605060
  • Pain frequency65
  • Recovery length55
  • Exercise load60
  • Clinician need60
  • Self-care fit50
  • Recurrence risk60

Clinician need

60 / 100

The knee is the body's largest joint and one of its most frequently injured, relying on ligaments and surrounding muscles rather than bony shape for stability.

Seven ways into this topic

01

Anatomy

How the knee's bones, ligaments, menisci, and muscles work together, and the typical range of motion for the joint.

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 02

Conditions

An overview of frequently diagnosed knee conditions, their relative severity, and how often each is seen in clinical practice.

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 03

Assessment

How clinicians examine the knee, including common orthopedic tests and warning signs that warrant urgent care.

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 04

Exercises

Commonly used knee exercises covering mobility, quadriceps and hip strengthening, and progressive functional loading.

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 05

Progression

A typical four-phase progression for knee rehabilitation, from symptom management to full functional loading.

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 06

Precautions

Common precautions and warning signs to be aware of while recovering from knee pain or injury.

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 07

Recovery

A general timeline for recovery from common knee conditions and the criteria clinicians use to judge readiness to return to full activity.

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Frequently asked questions

What is patellofemoral pain syndrome?
Patellofemoral pain syndrome describes pain around or behind the kneecap, often related to how the kneecap tracks in its groove during bending movements, and is common among runners and young active individuals.
What is the difference between the meniscus and the ACL?
The menisci are C-shaped cartilage cushions that absorb shock between the thigh and shin bones, while the anterior cruciate ligament (ACL) is one of several ligaments that control the knee's stability during rotation and forward sliding of the shin bone.
Does every meniscus tear need surgery?
Many meniscus tears, particularly smaller or degenerative tears in middle-aged and older adults, are managed successfully with exercise-based rehabilitation, while larger or mechanically unstable tears may be considered for surgical repair.
Is running bad for the knees?
Current evidence generally does not support the idea that recreational running increases the risk of knee osteoarthritis, and moderate running is often considered compatible with long-term joint health for most people.
What does a 'locked knee' mean?
A locked knee refers to an inability to fully bend or straighten the joint, often due to a displaced piece of torn meniscus or loose cartilage fragment, and typically warrants prompt evaluation.
How common is knee osteoarthritis?
Knee osteoarthritis is among the most common joint conditions affecting older adults, with prevalence increasing steadily with age and additional risk associated with prior injury and higher body weight.
What is IT band syndrome?
Iliotibial band syndrome describes pain at the outer knee related to irritation where the iliotibial band crosses the outside of the joint, common in runners and cyclists during periods of increased training load.
Can quadriceps weakness contribute to knee pain?
Reduced quadriceps strength is commonly associated with several knee conditions, since this muscle group plays a central role in absorbing load and controlling the kneecap's position during movement.

Sources & research

  1. Exercise for osteoarthritis of the kneeFransen M; et al. · 2015 · Cochrane DatabaseDOIPubMed
  2. Knee osteoarthritis clinical practice guidelinesKolasinski SL; et al. · 2020 · Arthritis Care & ResearchDOIPubMed

Media credits

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