Examination Findings in Knee Osteoarthritis
The key physical examination findings in knee osteoarthritis include joint line tenderness (particularly medial), joint effusion, decreased range of motion, crepitus, bony enlargement, and antalgic gait pattern. 1
Primary Physical Examination Findings
Pain and Tenderness
- Joint line tenderness is the most common finding, particularly at the medial compartment, reflecting the typical medial compartmental involvement in knee OA 1, 2
- Pain is characteristically localized to the affected compartment and worsens with weight-bearing activities 1
- Tenderness on palpation along the joint line is a reliable indicator of disease presence 2
Structural Changes
- Bony enlargement at the joint margins is frequently present and represents osteophyte formation 3
- Coarse crepitus is palpable or audible during passive and active range of motion, particularly in the patellofemoral compartment 2, 3
- Varus or valgus deformity may develop depending on which compartment is predominantly affected, with varus alignment being more common in medial compartment disease 2
Range of Motion and Function
- Decreased range of motion compared to the contralateral knee is characteristic, with both flexion and extension typically limited 1, 2
- Stiffness is present but typically lasts less than 30 minutes in the morning, distinguishing it from inflammatory arthritis 1
- Antalgic gait pattern (limping to avoid pain) is commonly observed during ambulation 1
Joint Effusion
- Joint effusion of varying severity is a frequent finding, though typically less pronounced than in inflammatory arthropathies 1, 2
- Effusions may be detected by ballottement or bulge sign testing 2
Associated Clinical Features
Functional Limitations
- Difficulty with weight-bearing activities such as stair climbing, prolonged standing, and walking are characteristic complaints 1
- Patients demonstrate decreased ability to perform activities of daily living due to pain and stiffness 3
Pain Characteristics
- Pain worsens with joint use and improves with rest in early disease 1
- In severe cases, rest pain and night pain may develop 3
Important Examination Considerations
Special Testing
- McMurray test for meniscal tears may elicit pain, as degenerative meniscal tears commonly coexist with OA 2
- However, a positive McMurray test does not necessarily indicate a surgically treatable meniscal tear in the context of OA 2
Alignment Assessment
- Careful assessment of limb alignment is essential, as malalignment contributes to disease progression and influences treatment decisions 2
- Varus deformity suggests medial compartment disease, while valgus deformity suggests lateral compartment involvement 2
Common Pitfalls to Avoid
- Failing to assess mechanical factors such as alignment and muscle weakness, which are critical for understanding disease progression and planning treatment 1
- Inadequate evaluation of other potential causes of knee pain such as referred pain from the hip, inflammatory arthritis, or periarticular pathology 1
- Overlooking the presence of effusion, which may indicate more active disease and could benefit from intra-articular corticosteroid injection 4
- Not considering that severe tenderness or warmth may suggest inflammatory or crystalline arthropathy rather than primary OA 2