Differential Diagnosis for Knee Pain
The patient's symptoms of pain below the knee cap, difficulty walking up and down stairs, pain when running, and discomfort when sitting and getting up from a chair, with relief when walking on a level surface, suggest several potential diagnoses. These can be categorized as follows:
Single Most Likely Diagnosis
- Patellofemoral Pain Syndrome (PFPS): This condition is characterized by pain in the front of the knee, usually around or behind the patella (kneecap). It is often associated with activities that put stress on the knee, such as climbing stairs, running, or getting up from a seated position. The pain pattern described matches closely with PFPS, making it the most likely diagnosis.
Other Likely Diagnoses
- Chondromalacia Patellae: A condition where the cartilage on the underside of the patella deteriorates and becomes soft. Symptoms include knee pain and tenderness, especially when climbing stairs or standing up after sitting for a while.
- Patellar Tendinopathy: Inflammation of the tendon that connects the patella to the shinbone, often caused by overuse. It leads to pain below the kneecap, especially when jumping, running, or climbing stairs.
- Osgood-Schlatter Disease: A condition that affects the upper part of the shinbone, where the patellar tendon attaches. It's common in adolescents and causes knee pain, especially when running, jumping, or climbing stairs.
Do Not Miss Diagnoses
- Deep Vein Thrombosis (DVT): Although less likely, DVT can cause leg pain and swelling. It's a serious condition that requires immediate medical attention because it can lead to pulmonary embolism.
- Septic Arthritis: An infection within a joint, which can cause severe pain, swelling, and difficulty moving the joint. It's a medical emergency that requires prompt treatment.
- Tumor: Bone or soft tissue tumors around the knee can cause pain and should be considered, especially if the pain is persistent and not clearly related to activity.
Rare Diagnoses
- Sinding-Larsen-Johansson Syndrome: A rare condition that affects the lower part of the patellar tendon, causing knee pain and swelling, typically in adolescents.
- Osteochondritis Dissecans: A joint condition in which a piece of cartilage, along with a thin layer of the bone beneath it, comes loose from the end of a bone because of inadequate blood supply. It can cause pain and swelling, especially if the fragment becomes detached and starts to float in the joint.