Physical Examination Findings of Knee Osteoarthritis
The diagnosis of knee osteoarthritis can be made clinically without imaging in patients over 40 years old who present with usage-related pain, short morning stiffness, and characteristic physical examination findings including joint line tenderness, bony enlargement, coarse crepitus, and reduced range of motion. 1, 2
Key Physical Examination Findings
Primary Signs
Joint line tenderness: Increased tenderness over the medial joint line is more common than lateral, reflecting the typical medial compartment predominance of knee OA 1, 3
Coarse crepitus: A crackling or grinding sensation palpable during passive or active knee motion, particularly in the patellofemoral compartment 3, 4, 2. This finding is associated with osteophytes at the patellofemoral and lateral tibiofemoral joints, and with meniscal tears 5
Bony enlargement: Palpable osteophytes and joint margin expansion, representing a hallmark sign of established OA 4, 2
Reduced range of motion: Passive arc of motion is typically limited compared to the contralateral knee (e.g., 10° to 100° versus 0° to 125° in normal knee) 1, 2
Secondary Signs
Joint effusion: Mild to moderate effusions are common, though inflammation is typically absent or only modest 1, 2
Gait abnormalities: Antalgic gait pattern may be present, with patients favoring the affected limb during ambulation 1
Muscle wasting: Quadriceps atrophy occurs with more severe disease 2
Joint deformity: Varus or valgus malalignment develops depending on disease severity and compartmental involvement 3
Clinical Diagnostic Approach
Imaging is not required to make the diagnosis in patients with typical presentation (usage-related pain, short duration morning stiffness, age >40, symptoms affecting one or few joints) 1. The physical examination findings listed above, combined with appropriate history, are sufficient for diagnosis in most cases.
When to Consider Imaging
- If there is unexpected rapid progression of symptoms or change in clinical characteristics 1
- To differentiate from inflammatory arthritis when diagnostic uncertainty exists 1
- When mechanical symptoms (locking, catching, giving way) suggest concomitant pathology such as meniscal tears 6, 7
Important Clinical Caveats
The majority of people over 70 years have asymptomatic meniscal tears, and the presence of a tear on imaging does not necessarily correlate with symptoms 6. The key distinguishing feature of a symptomatic tear is the presence of mechanical symptoms combined with focal tenderness 6.
Pain with internal hip rotation should prompt evaluation for hip OA rather than isolated knee pathology, as hip disease commonly refers pain to the knee 8.
Special provocative tests like McMurray's maneuver may cause increased pain in OA patients due to degenerative meniscal tears, but this does not necessarily indicate a surgically correctable lesion 3.