Rheumatology Case: Move it or Lose it

Periarticular muscle wasting is common in many forms of arthritis. In the absence of abnormal neurologic findings and marked weakness, EMG is not indicated. It would be very unusual for rheumatoid arthritis to cause this much damage to just the knee and not be evident in any other joints; therefore, ESR and RF are not indicated. Improperly fitting shoes may cause various pains in the legs, but would not explain the joint damage evident in this patient. Bone scans are often helpful in patients with diffuse pain or pain that is not clearly localized to a joint, but this patient’s pain is limited to her knee.

Serum uric acid will neither confirm nor eliminate gout in this case.

Arthroscopy would likely demonstrate other abnormalities of intraarticular structures, such as frayed cartilage. Given her history of knee trauma, an old tear of the cruciate ligament might be expected. However, her clinical is most consistent with the diagnosis of OA. Thus, arthroscopy is not needed to make the diagnosis.

Finding
A. Focal tenderness distal to the medial joint line of the knee
B. Tender bulging down into the calf muscles posteriorly
C. Distended prepatellar bursa
D. Tender and swollen tibial tubercle
E. Pain superior or lateral to the knee

Conditions
1. Prepatellar bursitis
2. Anserine bursitis
3. Osgood-Schlatter’s disease
4. Baker’s cyst, probably dissecting
5. Referred pain from the ipsilateral hip

A Baker’s cyst, also called a popliteal cyst, is an abnormal swelling of the semimembranosus gastrocnemius bursa. This bursa is located at the medial head of the gastrocnemius muscle. A one-way valve-like mechanism exists between the patellofemoral joint space and the bursa, and increased intraarticular pressure from a synovial effusion pushes fluid into this bursa. Excessive swelling or mild trauma to a modestly distended bursa may result in cyst rupture or dissection down into the posterior calf muscle. The result is pseudothrombophlebitis, which should be differentiated from deep venous thrombosis. Baker’s cysts are most commonly found in patients with significant effusions due to RA, OA, gout, and internal derangements of the knee.

Housemaid’s knee, or prepatellar bursitis, is swelling of the bursa overlying the kneecap. It typically occurs in patients with chronic trauma to the knees, as seen in religious professionals who frequently kneel to pray and in carpet layers. Minor acute trauma may also result in this disorder. The infrapatellar bursa, which sits inferiorly between the tibia and popliteal tendon, may similarly be involved. These bursae may become filled with fluid and infected, resulting in septic bursitis.

Osgood-Schlatter's disease is idiopathic osteochondrosis of the tibial tubercle. It is thought to represent a partial avulsion of the tibial tubercle at the insertion of the quadriceps muscle tendon, and occurs predominantly in boys aged 10 to 16. Tenderness and swelling over the tibial tubercle is typically found. In most patients, the disorder is self-limited and improves over a few years as the bone growth slows and the epiphysis closes.

Although hip pain is most commonly felt in the groin, occasionally pain is referred to an area superior or lateral to the knee. On physical examination, an apparently normal knee coupled with abnormal findings of the ipsilateral hip should arouse suspicion that the pain may be referred.

The synovial fluid is viscous, clear, and yellow with a WBC of 1,500/mm3, 90% mononuclear cells, and no crystals. Gram stain and culture were negative

A. Osteoarthrosis
B. Osteoarthritis
C. Traumatic osteoarthritis
D. Degenerative joint disease

The clinical signs and symptoms described here are designated by at least three diagnostic terms: osteoarthrosis , osteoarthritis , and degenerative joint disease. In addition, this patient’s history of previous trauma may have also produced joint instability that contributes to the current symptom complex.

The difference between the definitions of the first two terms is notable. Osteoarthrosis is the preferred diagnosis in the U.K. because “osis” means “an abnormal condition of.” In the U.S. osteoarthritis is the usual term. But “itis” implies “inflammation,” and since there is a minimal amount of inflammation detected in the joint fluid of individuals with osteoarthritis, the difference in terminology is intellectual. In other words, either term is correct.

The joint fluid aspirated from the painful right knee of this patient contained a low number of white blood cells, suggesting low-grade inflammation and would be consistent with a diagnosis of osteoarthritis.

Radiographs of this patient’s knees are consistent with those typically described in patients with osteoarthritis, including joint-space narrowing, osteophyte formation, and in some patients, subchondral cysts. The degree of pathology affecting each joint was probably not identical, even though weight-bearing radiographs of both knees were similar.

Arthroscopic studies have confirmed that radiographs may underestimate the degree of joint structure involvement. Interpretation of the findings in this case suggests that both diagnostic terms could be accurately applied, as both knees had osteoarthrosis and the right knee was inflamed as indicated by the presence of an effusion. The term “degenerative joint disease” may also be applied in cases such as this one, although it implies degeneration of the cartilage as the causative pathophysiologic process.

Other physical findings of note in this patient include quadriceps atrophy. A knee that is painful enough to prompt guarded movement can rapidly lead to deconditioning and produce muscle changes. The weakening of the quadriceps muscle can then exaggerate “micro-misuse” of the joint, resulting in increased knee pain. A vicious cycle is thus initiated, even in a mildly affected individual.

Therapeutic goals in patients with symptomatic osteoarthritis are to maintain and improve function of the affected joint and to relieve pain. This patient should be referred to physical therapy for a musculoskeletal and functional assessment and an exercise program. The assessment should include joint range of motion and alignment, neuromuscular fitness, and observational gait analysis. The goals of physical therapy for the patient with osteoarthritis include: (1) decreasing joint stress, (2) improving shock attenuation, (3) maintaining functional range of motion and strength, and (4) improving joint alignment. Therefore, the rehabilitation program should include instruction in exercises to maintain joint flexibility and improve muscular strength and endurance .

A graduated trial of medication is suggested for this patient. Current recommendations are to initiate therapy with simple analgesics such as acetaminophen followed by a careful trial of NSAIDs, either over-the-counter or in prescription strength. Topical capsaicin or salicylate-based creams may give some patients pain relief.

Intraarticular injection of a long-acting steroid may also be of benefit and should be considered early in patients with osteoarthritis and symptomatic effusions. In general, this therapy should not be used more than three times per year in any given joint. Intraarticular hyaluronate has been demonstrated in some studies to provide pain relief equal to NSAIDs for up to six months.

Patients with severe symptomatic osteoarthritis of the knee who have pain that has failed to respond to medical therapy and/or who have significant progressive limitation in their daily activities should be referred for orthopedic surgery for possible osteotomy or joint replacement. Joint lavage has been shown in a randomized control trial to be of no benefit.