Knee arthritis is one of the leading causes of disability in developed countries. In particular, arthritis of the patellofemoral joint causes pain in the anterior part of the joint, making it difficult for the patient to perform daily activities.
The patella lies in front of the knee, specifically at the point where the tibia is joined to the femur. It protects the knee and connects the muscles of the anterior surface with the tibia. The femoral end and the lower surface of the patella are covered by articular cartilage. This helps to smooth the sliding motion of the patella onto the femoral groove as the joint moves.
Arthritis of the patellar joint occurs when the articular cartilage along the femoral groove and the articular surface of the patella begin to degenerate. Over time, when the articular cartilage is worn, the underlying bones begin to rub with each other. This friction between the bone surfaces causes severe pain and inflammation.
Patellar fractures often cause damage to the articular cartilage that covers and protects the posterior surface of the bone. Even small displacements after fracture healing increase friction between the articular surfaces of the patella and the femur and thus the risk of arthritis of the patellar joint is greater.
Patellar dysplasia or hypoplasia of the lateral femoral condyle and the flattening of the intercondylar groove cause the patella not to properly move within the pulley and consequently lead to uneven load distribution that damage the cartilage. As a result, the articular cartilage of the patella is degenerated causing arthritis of the patellofemoral joint.
The main symptom of knee arthritis is pain and is located on the anterior surface of the knee. It may occur during periods of rest but most often it occurs after activities involving high forces on the patella, such as kneeling, climbing stairs and rising from low seats.
In addition, there is often a cracking sound heard during knee bending and stretching that can, at an advanced stage, block the knee when trying to extend it.
In general, the principles of treating arthritis of the patellofemoral joint are similar to those of knee arthritis and include:
- Non-steroidal Anti-Inflammatory Drugs (NSAIDs): Medications such as aspirin, naproxen and ibuprofen soothe pain and reduce edema.
- Exercise: Regular exercise can strengthen the knee joint. In addition, activities that strain the patellar joint, such as low seats, should be avoided. Thus, the patient is good to focus on activities that do not particularly strain the knee, such as walking and swimming.
- Weight Loss: In overweight patients, weight loss can relieve the knee from heavy loads exercised on a daily basis.
- Physiotherapy: Special exercises can increase the range of motion of the knee and strengthen the quadriceps by reducing load-charging of the patella. In the event of pain during exercise, the patient must stop and inform the Orthopedist.
- Injection therapy: Cortisone injections (steroids) relieve pain through their powerful anti-inflammatory action. In addition, intra-articular injections of hyaluronic acid may be performed.
If all conservative measures fail and the patient is not relieved of pain, surgical treatment is the next step. There are several alternatives and include:
- Chondroplasty: Performed arthroscopically, thin surgical instruments are inserted through small incisions around the knee and restore minor to moderate damage. With the method of chondroplasty, the surgeon smooths the rough arthritic surfaces, thus achieving natural replacement with fibrocartilage tissue.
- Correction of the patellar axis: It is achieved by a combined open release of the outer catheter joint and by the folding of the oblique portion of the medial flatus.
- Osteoarticular autografts: Healthy cartilage is obtained from another part of the knee and is used to cover a damaged area. This is a method that applies mainly to young patients.
- Transposition of the tibial tuberosity: In some cases the correction of the patellar axis is performed by translocating the tibial tuberosity (osteotomy) and fixing it inwards with screws. In this way the patella slides smoothly and with less friction on the femoral groove.
- Replacement of patellofemoral joint: This kind of “partial” knee replacement replaces the surface of the femoral groove with a thin metallic prosthesis and the articular surface of the patella with a plastic one and is held in place by acrylic cement.
In the case of lesions involving other parts of the knee, total knee arthroplasty is recommended.