Knee Osteoarthritis

Lower Limb

Overview

Knee osteoarthritis is a degenerative joint disease characterized by progressive loss of articular cartilage, osteophyte formation, and secondary changes in the joint capsule and surrounding tissues. It is the most common form of arthritis affecting the knee and typically presents with pain, stiffness, and functional limitation that worsens with activity and improves with rest. The condition may be primary (idiopathic) or secondary to prior trauma, alignment disorders, or inflammatory conditions.

Pathophysiology

Osteoarthritis of the knee involves breakdown of articular cartilage due to imbalance between load-bearing forces and the cartilage's capacity to withstand mechanical stress. Initial changes include cartilage softening and fibrillation, followed by progressive loss of cartilage thickness. Subchondral bone responds with sclerosis and osteophyte formation. Synovial inflammation may occur, releasing pro-inflammatory cytokines that further degrade cartilage.

Typical Presentation

Site

Medial knee compartment most common; lateral compartment or patellofemoral joint also affected; may be bilateral

Quality

Dull, aching pain; stiffness; clicking or grinding sensation (crepitus); occasional sharp pain with specific movements

Intensity

Mild to severe; typically 3-8/10 pain scale, varying with activity level and disease stage

Aggravating

Prolonged weight-bearing activities, walking downstairs, kneeling, squatting, prolonged sitting followed by movement initiation, cold damp weather, high-impact activities

Relieving

Rest, elevation, ice application, gentle movement after warm-up, anti-inflammatory medication, activity modification, compression

Associated

Morning stiffness (usually <30 minutes), swelling especially after activity, quadriceps weakness and atrophy, hamstring tightness, reduced knee flexion/extension ROM, gait dysfunction with antalgic pattern, nocturnal pain affecting sleep, functional limitations with stairs and transfers

Orthopaedic Tests

Test descriptions are written with AI assistance from standard clinical texts. Where a test lists Sources, its description has been checked against them; those sources are independent and do not endorse OsteoKit. Accuracy figures and grades (A–D) appear only when checked against the published study; tests without one are marked “No accuracy study”.

Further reading: full test procedures are described in standard clinical examination texts, e.g. Magee & Manske, Orthopedic Physical Assessment (7th ed.), and Cook & Hegedus, Orthopedic Physical Examination Tests: An Evidence-Based Approach (2nd ed.).

Grade A
A+ABCDStrong clinical value: substantially changes the diagnosis (LR ≥10 or ≤0.1)
useful both to rule in and rule out.

Lachman Test

Procedure

Patient supine, knee bent to 20–30°. Stabilise the lower femur with one hand and pull the upper tibia forwards with the other, comparing with the other knee.

Positive Finding

More forward movement than on the other side, with a soft or absent end-point.

Sensitivity / Specificity

85%/94%

Reference: Benjaminse A et al., J Orthop Sports Phys Ther 2006; PMID 16715828

Interpretation

Tests the anterior cruciate ligament. In osteoarthritis, osteophytes and stiffness can make it hard to interpret. An old ACL injury is a known cause of earlier osteoarthritis. Note: the Lachman test assesses anterior cruciate ligament integrity; its figures derive from ACL-rupture populations (Benjaminse 2006) and it appears here only to screen for a concomitant ACL injury, not knee osteoarthritis itself.

Sources

Grade B
A+ABCDGood clinical value: meaningfully changes the diagnosis in one direction (LR 5–10 or 0.1–0.2)
best for ruling IN (confirmation).

Thessaly Test

Procedure

Patient stands on the affected leg, holding your hands for balance, knee bent to 5°, and rotates the body and knee in and out three times; repeat at 20°.

Positive Finding

Joint line pain, locking or catching during rotation.

Sensitivity / Specificity

75%/87%

Reference: Smith BE et al., Evid Based Med 2015; PMID 25724195

Interpretation

A meniscal test. Degenerative meniscal tears are very common in knee osteoarthritis and rarely need surgery; pain on this test in an arthritic knee changes management little. Use caution with balance in older patients. Thessaly test at 20° of knee flexion for meniscal tears: pooled sensitivity 75%, specificity 87% (Smith 2015 meta-analysis). Evidence quality is low; use alongside history and other findings.

Sources

Classification

Kellgren-Lawrence Radiographic Grading

Procedure

Arranged by the treating doctor: weight-bearing X-rays of the knee, graded 0–4 for osteophytes, joint space narrowing, sclerosis and deformity.

Positive Finding

Grade 2 or higher (definite osteophytes) is the usual research definition of radiographic osteoarthritis.

Reference: Kellgren JH, Lawrence JS, 1957, Annals of the Rheumatic Diseases

Interpretation

Grades radiographic severity, which matches pain and function only loosely. Knee osteoarthritis can be diagnosed clinically without X-ray in people over 45 with activity-related pain and morning stiffness of 30 minutes or less. The Kellgren-Lawrence system is a radiographic severity grading scale, not a diagnostic test; a sensitivity/specificity pair is not applicable.

Sources

Questionnaire

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)

Procedure

The patient completes a 24-item questionnaire covering pain (5 items), stiffness (2 items) and physical function (17 items) over the past 48 hours.

Positive Finding

Higher scores mean more pain, stiffness and functional limitation. Record the baseline and repeat at review.

Reference: Bellamy N et al., 1988, Journal of Rheumatology

Interpretation

A validated outcome measure for tracking change with treatment, not a diagnostic test. WOMAC is a patient-reported outcome measure, not a diagnostic test.

Sources

Performance measure

Timed Up and Go (TUG) Test

Procedure

The patient rises from a standard chair, walks 3 metres at a comfortable pace, turns, walks back and sits down. Record the time and observe the walking.

Positive Finding

A slower time than at previous visits, or unsteady walking and turning.

Reference: Podsiadlo D, Richardson S, 1991, Journal of the American Geriatrics Society

Interpretation

A measure of mobility and falls risk used to track function over time. It is not a diagnostic test for osteoarthritis; published cut-offs for falls risk vary. TUG is a functional performance measure, not a diagnostic test for osteoarthritis.

Sources

Measurement

Weight-Bearing Line (Mechanical Axis) Assessment

Procedure

Arranged by the specialist: a full-length standing X-ray from hip to ankle to measure alignment.

Positive Finding

Varus (bow-legged) or valgus (knock-kneed) alignment.

Reference: Sharma L et al., 2001, Arthritis & Rheumatism

Interpretation

Varus alignment loads the medial compartment and valgus the lateral compartment, which affects progression. Used mainly when bracing or surgery such as osteotomy is being considered. Mechanical-axis assessment quantifies alignment/severity; it is not a diagnostic accuracy test.

Further reading

⚠ Red Flags

  • •Sudden onset severe knee pain with effusion and inability to bear weight (consider acute fracture or meniscal tear)
  • •Signs of infection: severe pain, marked swelling, warmth, erythema, fever (consider septic arthritis)
  • •Knee effusion with acute locked knee or giving way (consider meniscal tear or loose body)
  • •Unilateral knee pain with swelling, calf pain, warmth, or unilateral calf oedema (consider deep vein thrombosis and refer for duplex ultrasound). Homan's sign is unreliable (sensitivity roughly 10-54%, specificity roughly 39-89%) and must not be used to include or exclude DVT
  • •Rapid progressive pain and swelling out of proportion to mechanical findings (consider inflammatory arthropathy or malignancy)
  • •Neurological symptoms: numbness, tingling radiating down leg (consider nerve compression or radiculopathy)

⚡ Yellow Flags

  • •High pain catastrophizing and fear-avoidance beliefs limiting activity and rehabilitation compliance
  • •Depression or anxiety associated with chronic pain and functional limitation
  • •Social isolation and reduced activity participation due to mobility restrictions
  • •Excessive health anxiety or illness worry affecting treatment expectations
  • •Poor self-efficacy regarding pain management and exercise adherence
  • •Obesity or significant weight gain contributing to mechanical stress and pain persistence
  • •History of trauma or injury with ongoing litigation or compensation claims affecting motivation
  • •Inconsistent reporting of symptoms or non-anatomical pain distribution

Osteopathic Techniques

Exercise is the core treatment. Manual therapy added to exercise eases pain in the short term only; there is no long-term benefit.

Region

Tibiofemoral and patellofemoral joints

Technique

Articulation, knee (tibiofemoral and patellofemoral)
Grade C
Limited evidence: indirect or low-quality support only
Adds short-term pain relief to exercise (very low to moderate certainty). No long-term benefit.

Rationale

Gentle, rhythmic glides of the knee and kneecap within their range to ease pain and stiffness.

How it's done, cautions & evidence

How it's done

Passive, low-velocity glides of the knee within its range, with no thrust: distraction and front-to-back glides of the tibia on the femur, and glides of the kneecap in each direction, usually 2–3 oscillations a second for 1–2 minutes. A Mulligan variant holds a sustained glide of the tibia while the patient actively bends and straightens the knee.

Cautions

In knee osteoarthritis trials, no serious adverse events were reported with manual therapy.

Evidence in Knee Osteoarthritis

Runge 2022 (19 trials, knee and hip osteoarthritis): manual therapy added to exercise helped pain in the short term (very low to moderate certainty) but not in the long term (high certainty). Zhu 2024 (25 trials, knee osteoarthritis): manual therapy eased pain more than usual care or exercise in the short term (low quality), with no serious adverse events.

Region

Quadriceps and the tissues around the knee

Technique

Soft tissue, knee and quadriceps
Grade C
Limited evidence: indirect or low-quality support only
Massage eased pain and stiffness in the short term. No long-term benefit.

Rationale

Hands-on work to the quadriceps and the tissues around the knee to ease tension and pain.

How it's done & evidence

How it's done

Hands-on kneading, stroking and sustained pressure to the quadriceps, the patellar and quadriceps tendons, the iliotibial band near the knee and the tissues around the joint. Transverse friction massage across a tendon is one form. In trials it was given alongside exercise.

Evidence in Knee Osteoarthritis

Wu 2022 (12 trials, 737 people): massage reduced pain and stiffness after 1–4 weeks, and stiffness and function after 6–8 weeks, with no difference in the long term. GRADE certainty low to moderate.

Region

Hip and thigh muscles

Technique

Muscle energy, hip and thigh musclesNo trials found

Rationale

Low-force, patient-powered stretch for tight hip and thigh muscles.

How it's done, cautions & evidence

How it's done

The muscle (for example the hamstrings, adductors or rectus femoris) is taken to its barrier. The patient pushes gently, at about 10–20% effort, against resistance for 5–10 seconds, relaxes for 3–5 seconds, and the new barrier is taken up.

Cautions

Not used with an acute fracture, a joint infection or a bone malignancy; take care with severe osteoporosis or after surgery that limits muscle contraction. Use the least force needed: too much can tear a muscle or pull off a tendon, especially in older patients.

Evidence in Knee Osteoarthritis

Searched 24 Oct 2026: no trials of hip muscle energy technique in knee osteoarthritis.

Region

Ankle and foot (talocrural and subtalar joints)

Technique

Articulation, ankle and foot
Grade D
Low evidence: expert consensus or could not be verified against literature
No trials of ankle articulation by a practitioner in knee osteoarthritis. One trial of machine-assisted ankle dorsiflexion could not show extra benefit over exercise.

Rationale

Gentle ankle and foot glides to keep dorsiflexion for walking. An add-on to exercise; not tested by hand in knee OA.

How it's done, cautions & evidence

How it's done

Passive, rhythmic, low-velocity glides of the ankle (talocrural), subtalar, midfoot and toe joints, within or up to the end of the available range, often aimed at restoring ankle dorsiflexion.

Cautions

Before mobilising an acute ankle injury, check for fracture with the Ottawa ankle rules (tenderness over either malleolus), and palpate the base of the 5th metatarsal, the navicular and the midfoot for a Lisfranc injury.

Evidence in Knee Osteoarthritis

Searched 27 Oct 2026: no trials of ankle or foot articulation by a practitioner in knee osteoarthritis. Fung 2021 (RCT, n=73 older adults) added 30° or 5° of passive ankle dorsiflexion with an apparatus to exercise: both groups improved in WOMAC and pain, with no significant difference, so any benefit over exercise alone is unclear.

Rehabilitation Exercises

Knee Flexion and Extension - Seated

Range of MotionBeginner

Ankle Pumps and Knee Mobilization

Range of MotionBeginner

Quadriceps Stretch - Standing

StretchingBeginner

Hamstring Stretch - Supine or Seated

StretchingBeginner

Quadriceps Sets with Glute Activation

StrengtheningBeginner

Straight Leg Raise - Supine

StrengtheningIntermediate

Step-ups on Low Step

StrengtheningIntermediate

Calf Raises - Double Limb

StrengtheningIntermediate

Tandem Standing or Single Leg Standing

BalanceIntermediate

Hip Abductor Activation - Side-Lying Leg Lifts

PosturalIntermediate

Aquatic Walking or Shallow Water Aerobics

CardiovascularIntermediate

Mini Squats or Sit-to-Stand from Chair

BalanceAdvanced

Referral Criteria

  • •Acute onset severe pain with effusion, warmth, and fever suggesting septic arthritis requiring urgent medical evaluation
  • •Mechanical symptoms (locking, catching) consistent with meniscal tear unresponsive to conservative management; may require imaging and orthopedic consultation
  • •Rapid functional decline or severe pain unresponsive to conservative osteopathic and physiotherapy management after 6-8 weeks; consider orthopedic assessment for surgical options
  • •Bilateral knee pain with systemic symptoms suggesting inflammatory arthropathy (rheumatoid arthritis, psoriatic arthritis); refer to rheumatology
  • •Significant knee effusion with signs of instability or giving way; may require MRI and orthopedic evaluation
  • •Neurological symptoms including numbness, tingling, or weakness suggesting referred pain from lumbar spine or nerve compression; refer to spine specialist
  • •Severe functional limitation affecting activities of daily living and quality of life despite conservative management; consider orthopedic consultation regarding knee replacement candidacy
  • •Signs of deep vein thrombosis (unilateral swelling, calf pain, warmth); refer urgently to vascular medicine or emergency department
  • •Skin changes, infection signs, or open wound over knee joint; refer to wound care or infectious disease specialist