What causes a pinching sensation in the knees?

Pinching Sensation in Knees: Differential Diagnosis and Evaluation

A pinching sensation in the knees most commonly indicates fat pad impingement (Hoffa's disease), medial plica syndrome, or meniscal pathology, though referred pain from the lumbar spine or hip must be excluded before attributing symptoms solely to knee pathology. 1, 2

Primary Knee-Specific Causes

Fat Pad Impingement Syndromes

• Fat pad impingement and Hoffa's disease are characterized by enhancing synovitis >2mm in Hoffa's fat pad and correlate specifically with peripatellar "pinching" sensations. 1, 2
• This condition results from repeated minor trauma and overuse, typically presenting as anterior or peripatellar discomfort. 3
• The fat pad can become inflamed and mechanically impinged between the patella and femur during knee extension. 3

Medial Plica Syndrome

• Medial plicae are synovial folds that can cause anterior knee pain with a characteristic "catching" or pinching quality. 1, 2
• This condition is closely related to overuse and repeated minor trauma, often triggered by increased or changed activity patterns. 3

Meniscal Pathology

• Meniscal tears affect approximately 12% of adults and can produce mechanical symptoms including pinching sensations, particularly with rotation or weight-bearing. 4
• The McMurray test (concurrent knee rotation and extension) has 61% sensitivity and 84% specificity for meniscal tears. 4
• Joint line tenderness demonstrates 83% sensitivity and 83% specificity for meniscal pathology. 4

Critical Differential: Referred Pain Sources

Before attributing pinching sensations exclusively to knee pathology, lumbar spine and hip pathology must be systematically excluded. 1, 2

Lumbar Spine Pathology

• Lumbar spine disease, including nerve root compression and spinal stenosis, must be considered when knee radiographs are unremarkable and clinical evidence suggests spinal origin. 5, 1
• A thorough clinical examination of the lumbar spine should precede knee-focused imaging. 1
• Neurologic testing including pinprick sensation, vibration perception, pressure sensation, and ankle reflexes are recommended for screening distal symmetric polyneuropathy that may mimic knee symptoms. 5

Hip Pathology

• Hip pathology commonly refers pain to the knee and should be evaluated if knee imaging is normal. 1, 2
• Consider hip radiographs if knee examination and imaging are unrevealing. 2

Diagnostic Algorithm

Initial Clinical Evaluation

• Localize the pinching sensation anatomically: anterior (fat pad, plica), medial (meniscus, medial compartment), lateral (ITB syndrome, lateral meniscus), or posterior (Baker's cyst, hamstring tendinopathy). 1, 2
• Perform McMurray test and assess for joint line tenderness if meniscal pathology is suspected. 4
• Examine lumbar spine and hip before concluding the pain originates from the knee itself. 1, 2

Imaging Sequence

• Obtain anteroposterior and lateral knee radiographs first to exclude fractures, osteoarthritis, osteophytes, and loose bodies. 1, 6
• If radiographs are normal or show only effusion but pinching sensation persists, MRI without IV contrast is indicated. 1, 6
• MRI is excellent for identifying meniscal tears, ligamentous lesions, bone marrow edema, fat pad pathology, and Baker's cysts. 2
• Consider hip radiographs if knee examination and imaging are non-revealing. 2

Age-Specific Considerations

Younger Patients (<40 years)

• Patellofemoral pain syndrome affects approximately 25% of physically active individuals under 40 years and presents with anterior knee pain during squatting (91% sensitivity, 50% specificity). 4, 7
• Acute meniscal tears from twisting injuries are more common in this age group. 4
• Patellar tracking problems including subluxation are more likely in teenage girls and young women. 7

Older Patients (≥45 years)

• Knee osteoarthritis is the most likely diagnosis in patients ≥45 years presenting with activity-related knee pain (95% sensitivity, 69% specificity). 4
• Degenerative meniscal tears are common and may coexist with osteoarthritis. 4
• Not all meniscal tears are symptomatic, particularly in patients over 45 years. 1

Common Diagnostic Pitfalls

• Do not order MRI without recent radiographs first—approximately 20% of patients with chronic knee pain inappropriately receive MRI without radiographs. 1, 6
• Do not overlook referred pain from hip or lumbar spine before attributing symptoms exclusively to knee pathology. 1, 2
• In patients over 70 years, bilateral structural abnormalities can exist with primarily unilateral symptoms. 1
• Radiographs may be initially normal in subchondral insufficiency fractures, which later show articular surface fragmentation. 1

Initial Management Approach

Conservative Treatment

• First-line management consists of activity modification, exercise therapy focusing on hip and knee strengthening, and patient education. 4
• For patellofemoral-related pinching, hip and knee strengthening exercises combined with foot orthoses or patellar taping are recommended. 4
• For meniscal tears (including those with mechanical symptoms), exercise therapy for 4-6 weeks is appropriate as first-line treatment. 4

When to Consider Advanced Intervention

• Surgical referral for meniscal tears is indicated only for severe traumatic bucket-handle tears with displaced meniscal tissue. 4
• For degenerative meniscal tears, surgery is not indicated even in the presence of mechanical symptoms like catching or locking. 4