Knee Osteoarthritis
Lower LimbOverview
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. Contributing factors include mechanical malalignment (varus/valgus), muscle weakness (especially quadriceps), obesity increasing joint loading, prior meniscal tears, ligamentous laxity, and proprioceptive deficits. The condition is influenced by genetic predisposition, age, sex (higher in women post-menopause), and cumulative joint trauma.
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
Kellgren-Lawrence Radiographic Grading
Procedure
Obtain weight-bearing anteroposterior and lateral knee radiographs. Score the degree of joint space narrowing, osteophytes, sclerosis, and deformity on a 0-4 scale (0=normal, 4=severe).
Positive Finding
Grade 2 or higher (definite osteophytes and possible joint space narrowing) indicates radiographic osteoarthritis
Sensitivity / Specificity
94% / 88%
Kellgren JH, Lawrence JS, 1957, Annals of the Rheumatic Diseases
Interpretation
Establishes presence and severity of radiographic OA; correlates imperfectly with symptoms and functional limitation
Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)
Procedure
Patient completes a 24-item questionnaire assessing pain (5 items), stiffness (2 items), and physical function (17 items) over the past 48 hours using a 0-4 Likert scale.
Positive Finding
Higher scores indicate greater pain, stiffness, and functional limitation; scores >30 suggest clinically significant symptoms
Sensitivity / Specificity
Unknown / Unknown
Bellamy N et al., 1988, Journal of Rheumatology
Interpretation
Reliable outcome measure for symptom severity and functional impairment in knee OA; commonly used for tracking treatment response
Lachman Test
Procedure
Patient supine, knee flexed 20–30°. Examiner stabilizes distal femur with one hand and pulls proximal tibia anteriorly with the other, assessing anterior tibial translation and endpoint quality.
Positive Finding
Excessive anterior tibial translation (>5 mm) or soft/absent endpoint suggests anterior cruciate ligament insufficiency
Sensitivity / Specificity
72–98% / 93–96%
Benjaminse A et al., 2006, British Journal of Sports Medicine
Interpretation
Detects ACL injury; may be relevant in OA patients with concurrent ligamentous laxity contributing to instability and degeneration
Thessaly Test
Procedure
Patient stands on one leg with knee flexed 5° and 20° alternately while internally and externally rotating the tibia 3 times. Examiner notes reproduction of pain or catching sensation.
Positive Finding
Reproduction of joint line pain, catching, or locking suggests meniscal pathology
Sensitivity / Specificity
94% (at 20° flexion) / 96% (at 20° flexion)
Karachalios T et al., 2005, Arthritis & Rheumatism
Interpretation
Detects meniscal tears; high accuracy in identifying concurrent meniscal damage in OA knees, which may influence symptom severity
Timed Up and Go (TUG) Test
Procedure
Patient rises from a chair, walks 3 metres at comfortable pace, turns, returns to chair, and sits down. Time is recorded in seconds.
Positive Finding
Performance >12 seconds indicates functional limitation and increased fall risk
Sensitivity / Specificity
79–95% (for functional impairment in OA) / See current literature
Podsiadlo D, Richardson S, 1991, Journal of the American Geriatrics Society
Interpretation
Practical measure of mobility and functional capacity in OA; predicts disability progression and quality of life
Weight-Bearing Line (Mechanical Axis) Assessment
Procedure
Full-length weight-bearing radiograph (hip-knee-ankle view) is obtained to determine alignment of the mechanical axis passing through the femoral head, knee centre, and talus.
Positive Finding
Varus alignment (medial OA) or valgus alignment (lateral OA) of >3° deviation from neutral predicts location and progression of compartmental OA
Sensitivity / Specificity
See current literature / See current literature
Sharma L et al., 2001, Arthritis & Rheumatism
Interpretation
Identifies malalignment as a risk factor for OA progression; informs treatment decisions (e.g. bracing, realignment osteotomy)
⚠ 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, and positive Homan's sign (consider deep vein thrombosis)
- •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
Region
Knee joint (tibiofemoral and patellofemoral articulations)
Technique
Articulation
Rationale
Gentle passive and active-assisted range of motion articulation promotes synovial fluid distribution, maintains cartilage nutrition, reduces stiffness, and helps restore normal arthrokinematics. Rhythmic mobilization within pain-free ranges stimulates mechanoreceptors and may provide pain relief through gate control mechanism.
Region
Quadriceps muscle group and knee extensors
Technique
Soft Tissue
Rationale
Soft tissue techniques address muscular tension, trigger points, and fascial restrictions that contribute to quadriceps weakness and altered knee mechanics. Improved tissue quality enhances muscle activation and reduces compensatory patterns affecting knee stability.
Region
Hip joint, lumbar spine, and kinetic chain
Technique
MET
Rationale
Muscle Energy Techniques address hip flexor tightness, gluteal weakness, and spinal mobility restrictions that alter lower limb biomechanics and increase knee load. Restoring hip and lumbar function reduces compensatory stress on the knee joint.
Region
Knee joint capsule, ligaments, and periarticular tissues
Technique
Soft Tissue
Rationale
Gentle soft tissue mobilization of joint capsule, collateral ligaments, and surrounding fascia improves proprioception, reduces pain through neuromodulation, and facilitates normal joint mechanics and fluid dynamics.
Region
Foot and ankle (subtalar and talocrural joints)
Technique
Articulation
Rationale
Ankle and foot mechanics influence lower limb alignment and load distribution through the knee. Restoring ankle dorsiflexion, plantarflexion, and eversion improves gait mechanics and reduces abnormal knee loading patterns.
Region
Anterior and posterior knee compartments including lymphatic drainage
Technique
Lymphatic
Rationale
Lymphatic techniques promote fluid drainage from periarticular tissues, reduce swelling and effusion, enhance nutrient delivery to joint structures, and support the body's natural healing and inflammatory resolution processes.
Add-On Approaches
Chinese Medicine
Acupuncture targeting local points (ST35 Dubi, ST36 Zusanli, GB34 Yanglingquan, LV3 Taichong) and distal points may modulate pain perception and improve qi circulation. Moxibustion may be beneficial for cold-damp presentations. Herbal medicine addressing kidney yang deficiency and blood stasis may support tissue healing and reduce inflammation.
Chiropractic
Knee manipulation (where appropriate and not contraindicated by severity) combined with correction of lower limb alignment, foot orthotics for arch support, and analysis of gait mechanics may reduce abnormal joint loading. Lower back and hip assessment to ensure proper kinetic chain alignment.
Physiotherapy
Progressive lower limb strengthening (especially quadriceps, hamstrings, and hip abductors), balance and proprioceptive training, gait re-education, cardiovascular conditioning, and structured exercise programs (aquatic therapy particularly beneficial) are core evidence-based interventions. Weight management counseling and functional training for activities of daily living.
Remedial Massage
Deep tissue massage of quadriceps, hamstrings, gastrocnemius, and lateral thigh structures addresses muscle tension and trigger points. Cross-friction techniques to ligamentous structures and soft tissue mobilization improve tissue extensibility and proprioceptive input.
Rehabilitation Exercises
Knee Flexion and Extension - Seated
Ankle Pumps and Knee Mobilization
Quadriceps Stretch - Standing
Hamstring Stretch - Supine or Seated
Quadriceps Sets with Glute Activation
Straight Leg Raise - Supine
Step-ups on Low Step
Calf Raises - Double Limb
Tandem Standing or Single Leg Standing
Hip Abductor Activation - Side-Lying Leg Lifts
Aquatic Walking or Shallow Water Aerobics
Mini Squats or Sit-to-Stand from Chair
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