Intra-Articular Injection of the Knee Joint—Medial Mid-Patellar Approach

Indications and Clinical Considerations

The knee joint is susceptible to developing arthritis from a variety of conditions that all have the ability to damage the joint cartilage. Osteoarthritis of the joint is the most common form of arthritis that results in knee joint pain ( Fig. 148.1 ). However, rheumatoid arthritis and posttraumatic arthritis also are common causes of knee pain secondary to arthritis. Less common causes of arthritis-induced knee pain include the collagen vascular diseases, infection, villonodular synovitis, and Lyme disease. Acute infectious arthritis usually is accompanied by significant systemic symptoms, including fever and malaise, and should be easily recognized by the astute clinician and treated appropriately with culture and antibiotics, rather than injection therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the knee joint, although knee pain secondary to collagen vascular disease responds exceedingly well to the intra-articular injection technique described later.

The majority of patients with knee pain secondary to osteoarthritis and posttraumatic arthritis pain report pain localized around the knee and distal femur. Activity makes the pain worse; rest and heat provide some relief. The pain is constant and characterized as aching. The pain may interfere with sleep. Some patients note a grating or popping sensation with use of the joint, and crepitus may be present on physical examination.

In addition to the previously mentioned pain, patients with arthritis of the knee joint often experience a gradual decrease in functional ability with decreasing knee range of motion, making simple everyday tasks, such as walking, climbing stairs, and getting in and out of cars, quite difficult. Morning stiffness and stiffness after sitting for prolonged periods are commonly reported by patients with arthritis of the knee. With continued disuse, quadriceps muscle weakness and wasting may occur, and loss of support from the muscles and ligaments eventually makes the knee joint unstable. This instability is most evident when the patient attempts to walk on uneven surfaces or climb stairs.

Plain radiographs are indicated for all patients with knee pain. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging of the knee is indicated if internal derangement or occult mass or tumor is suspected ( Fig. 148.2 ).

Clinically Relevant Anatomy

The rounded condyles of the femur articulate with the condyles of the tibia below and the patella anteriorly ( Fig. 148.3 ). The articular surface is covered with hyaline cartilage, which is susceptible to arthritis. The joint is surrounded laterally and posteriorly by a capsule that provides support for the joint. The capsule is absent anteriorly, and in its place are the suprapatellar and infrapatellar bursae. Laterally and medially, the joint is strengthened by the tendons of the vastus lateralis and medius muscles. Posteriorly, the joint is strengthened by the oblique popliteal ligament. Also adding to the strength of the joint are a variety of extracapsular ligaments that include the following: the medial and lateral collateral ligaments and the ligamentum patellae anteriorly and the oblique popliteal ligament posteriorly. Within the joint capsule, there are also a variety of ligaments that add to the strength of the joint, including the anterior and posterior cruciate ligaments.

The joint capsule is lined with a synovial membrane that attaches to the articular cartilage and gives rise to a number of bursae, including the suprapatellar and infrapatellar bursae. The knee joint is innervated by the femoral, obturator, common peroneal, and tibial nerves. In addition to arthritis, the knee joint is susceptible to the development of tendinitis, bursitis, and disruption of the ligaments, cartilage, and tendons.