What is the diagnosis and recommended treatment for a 76-year-old female with acute onset of right knee pain and a 'tearing' sensation after a kneeling episode, presenting with sharp pain and limited mobility?

Medical Impression: Patellar Tendon Rupture

This 76-year-old female has sustained an acute patellar tendon rupture based on the classic presentation of sudden "tearing" sensation below the patella during kneeling, immediate severe pain, inability to bear weight comfortably, and the characteristic "scratching/rubbing" sensation during weight-bearing attempts.

Clinical Diagnosis

The clinical presentation is pathognomonic for patellar tendon rupture:

• Mechanism of injury: Sudden eccentric quadriceps contraction during kneeling with audible/palpable "tearing" or "let-go" sensation is the classic mechanism for patellar tendon rupture 1, 2
• Pain pattern: Sharp, localized pain (8/10) during weight-bearing that dramatically improves at rest (1-2/10) indicates complete structural failure rather than tendinopathy 1
• Functional deficit: The "scratching/rubbing" sensation during weight-bearing suggests loss of normal extensor mechanism continuity with abnormal patellar movement 2
• Pain-free passive motion: Absence of pain during knee flexion/extension at rest distinguishes this from inflammatory conditions or osteoarthritis 3

Immediate Diagnostic Workup

Obtain bilateral knee radiographs (AP, lateral, and Merchant views) immediately to confirm the diagnosis and assess for patella alta 4:

• Lateral radiograph will show patella alta (high-riding patella) on the affected side compared to the contralateral knee, which is diagnostic for patellar tendon rupture 1, 2
• Radiographs exclude other pathology such as patellar fracture or avulsion injuries 4
• Bilateral views are essential for comparison to identify subtle patella height differences 1

If radiographs are equivocal or clinical suspicion remains high, obtain ultrasound or MRI 4:

• Ultrasound has nearly 100% sensitivity and specificity for complete patellar tendon tears and can be performed immediately at bedside 4, 1
• MRI is reserved for uncertain diagnoses or surgical planning but should not delay treatment 4, 2

Physical Examination Findings to Confirm

Perform these specific examination maneuvers 1, 2:

• Palpable defect: Feel for a gap in the patellar tendon just below the inferior pole of the patella (highly specific for complete rupture) 1, 2
• Straight leg raise test: Inability to actively extend the knee or perform straight leg raise against gravity confirms complete extensor mechanism disruption 1, 2
• Patella position: Visual inspection may reveal high-riding patella compared to contralateral side 2

Definitive Treatment

Urgent orthopedic surgical referral within 24-48 hours is mandatory for complete patellar tendon rupture 1, 2:

• Time to surgery is the single most important prognostic factor - delays beyond 2 weeks significantly worsen outcomes and may require reconstruction rather than primary repair 2
• Surgical repair involves transosseous tunnels or suture anchor techniques with high-strength non-absorbable sutures in running locking fashion 1
• Early repair (within 2 weeks) allows direct end-to-end repair; chronic tears require augmentation or reconstruction 1, 2

Immediate Management Prior to Surgery

Immobilize the knee in full extension immediately 2:

• Apply knee immobilizer or long leg splint in full extension to prevent further tendon retraction 2
• Non-weight-bearing status with crutches until surgical repair 2
• Ice application for pain and swelling control 4
• Avoid NSAIDs immediately before surgery due to bleeding risk, but can use acetaminophen for pain 3

Do not attempt physical therapy or range of motion exercises prior to surgical repair - this will worsen the tear and increase tendon retraction 1, 2.

Common Pitfalls to Avoid

Do not mistake this for patellar tendinopathy or bursitis 4:

• Tendinopathy presents with gradual onset, load-related pain that improves with warm-up, and no acute tearing sensation 4
• The acute traumatic mechanism, immediate severe pain, and functional deficit distinguish rupture from tendinopathy 1, 2

Do not delay surgical referral for "conservative management" 2:

• Complete patellar tendon ruptures require surgical repair - conservative management is only appropriate for partial tears 1, 2
• Each day of delay worsens prognosis and may necessitate more complex reconstruction 2

Do not rely solely on clinical examination if uncertain 4:

• Obtain imaging (radiographs first, then ultrasound if available) to confirm the diagnosis 4, 1
• Partial tears can be managed conservatively but require imaging to differentiate from complete tears 2

Risk Factors Present in This Patient

Age-related tendon degeneration increases rupture risk 2, 5:

• Patients over 60 years have chronically weakened tendons predisposed to rupture from low-energy mechanisms 2, 5
• Systemic conditions (diabetes, hypertension) and certain medications (statins, fluoroquinolones) further weaken tendons 5

Expected Postoperative Course

Rehabilitation begins immediately after surgery with protected weight-bearing 1, 2:

• Knee immobilizer locked in extension for 2-6 weeks with progressive unlocking 1, 2
• Protected weight-bearing as tolerated in locked brace 1
• Passive range of motion in "safe zone" (0-60 degrees) starting week 2-4 1
• Active extension avoided for 6 weeks to protect repair 1
• Return to normal activities expected by 6 months 2