Signs and Symptoms of Knee Arthritis
The cardinal clinical features of knee osteoarthritis are persistent knee pain (typically mechanical, worsening with activity), limited morning stiffness (usually less than 30 minutes), reduced function, crepitus on movement, restricted range of motion, and bony enlargement of the joint. 1
Primary Symptoms
Pain Characteristics
- Mechanical pain that worsens with weight-bearing activities and improves with rest 2
- Gradual onset that progresses slowly over time 3
- Initially presents as self-limiting episodes, but may become nearly constant as disease advances 3
- Pain location varies by compartment affected:
Stiffness
- Short-duration morning stiffness (typically less than 30 minutes) 1, 5
- Inactivity stiffness that improves with movement 1
- This brief stiffness pattern distinguishes osteoarthritis from inflammatory arthritis, which typically causes prolonged morning stiffness exceeding one hour
Functional Limitations
- Reduced walking distance and difficulty with stairs 2
- Progressive limitation in activities of daily living 6
- Decreased ability to perform work-related tasks 1
Physical Examination Findings
Most Reliable Signs
The most diagnostically useful physical findings include 5:
- Crepitus: Coarse grinding sensation with joint movement (interobserver reliability κ = 0.78) 7
- Bony enlargement: Palpable osteophytes at joint margins (interobserver reliability κ = 0.66) 7
- Joint line tenderness: Particularly over medial compartment (interobserver reliability κ = 0.76) 7
- Restricted range of motion: Reduced flexion and extension compared to contralateral side 2, 7
Additional Findings
- Mild knee effusion (detectable by ballottement or bulge sign) 2
- Quadriceps muscle wasting in chronic cases 7
- Antalgic gait pattern 2
Diagnostic Probability
When all six key features are present (persistent pain, limited morning stiffness, reduced function, crepitus, restricted movement, and bony enlargement), the probability of radiographic knee osteoarthritis approaches 99% in adults over age 45. 5 This assumes a baseline prevalence of 12.5% in this age group.
Clinical Pitfalls
Poor Correlation with Imaging
There is notably poor correlation between radiological severity and symptom intensity 3. Patients may have significant radiographic changes with minimal symptoms, or vice versa. Clinical assessment should drive management decisions, not imaging alone.
Age Considerations
Symptoms typically manifest in adults over age 40, with risk increasing substantially with age 1. Nearly one in two people develop symptomatic knee OA by age 85 2.
Gender Differences
Women represent 78% of diagnosed cases despite being only 51% of the general population 1, and experience higher prevalence, particularly after menopause.
Advanced Disease Features
In severe cases, additional symptoms emerge 6:
- Rest pain and night pain
- Joint deformity (varus or valgus malalignment)
- "Activated osteoarthritis" with acute inflammatory episodes and effusion 4
Risk Factors to Assess
When evaluating suspected knee arthritis, consider 2:
- Obesity (BMI ≥25 kg/m²)
- Previous knee trauma or surgery
- Occupational factors (repetitive bending, heavy lifting)
- Genetic predisposition and family history
- Female sex and age over 40