What is the cause of sharp, stabbing left hip pain, exacerbated by walking and relieved by sitting, with associated numbness, tingling, and popping sensations, in a patient with a history of left knee surgery, who experiences pain reduction with Tylenol (acetaminophen)?

Trochanteric Bursitis: This condition is characterized by sharp, stabbing pain in the outer hip, which worsens with activity and improves with rest. The patient's symptoms of sharp, stabbing pain in the left posterior hip and anterior joint, exacerbated by walking and relieved by sitting, are consistent with trochanteric bursitis. The absence of swelling, discoloration, and back pain also supports this diagnosis.

Piriformis Syndrome: This condition occurs when the piriformis muscle irritates the sciatic nerve, causing pain, numbness, and tingling in the hip and leg. The patient's symptoms of numbness, tingling, and pain in the left hip and leg, particularly with activity, are consistent with piriformis syndrome.
Iliopsoas Tendinopathy: This condition is characterized by pain and stiffness in the hip and groin area, often exacerbated by activity. The patient's history of left knee surgery and inability to straighten the left knee may have led to altered biomechanics, contributing to iliopsoas tendinopathy.
Gluteus Medius Tendinopathy: This condition is characterized by pain and weakness in the outer hip, often exacerbated by activity. The patient's symptoms of sharp, stabbing pain in the left posterior hip are consistent with gluteus medius tendinopathy.

Avascular Necrosis (AVN) of the Femoral Head: This condition occurs when the blood supply to the femoral head is disrupted, leading to necrosis of the bone tissue. AVN can cause severe, persistent pain in the hip and groin area, and is often associated with a history of trauma or steroid use. Although the patient did not experience a fall or twisting injury, AVN is a potentially devastating condition that should not be missed.
Septic Arthritis: This condition occurs when the joint space becomes infected, leading to severe pain, swelling, and stiffness. Although the patient does not have fever, swelling, or discoloration, septic arthritis is a medical emergency that requires prompt diagnosis and treatment.

Osteoid Osteoma: This condition is a rare, benign bone tumor that can cause severe, persistent pain in the hip and leg. The patient's symptoms of sharp, stabbing pain in the left hip and leg are consistent with osteoid osteoma, although this diagnosis is less likely given the absence of night pain and other characteristic features.
Slipped Capital Femoral Epiphysis (SCFE): This condition occurs when the femoral head slips out of place, leading to pain and stiffness in the hip and leg. Although SCFE is more common in adolescents, it can occur in adults, particularly those with a history of trauma or underlying medical conditions.