Over the past few years, we have seen patients with knee disorders with the same characteristics of long distance travel, overexertion, and a relatively strong physique, with sudden onset of knee pain, inability to straighten the knee, but also incomplete flexion, severe pain behind the knee, and no significant swelling of the joint. Physical examination findings are often mistaken for meniscal injury due to the inability to fully straighten or flex, or the patient’s suspected pain in the medial or lateral joint space. X-ray examinations mostly only reveal synovial swelling, and MRI findings are even more confusing in most hospitals because of the high resolution of MRI, and degeneration of the meniscus, ligaments, and cartilage can be mistaken for injury, but MRI will reveal posterior group muscle of extensive congestion and edema. The sensitivity of physical examination is also compromised in this disease. I personally know that the patient should be examined in the prone position, and painful points and tense tendons can be palpated at the stops of the biceps femoris, semitendinosus, and semimembranosus muscles. A careful examination of the meniscus or meniscal grind test or steinman’s test can still rule out meniscal injury. This pain is actually muscle spasm caused by overexertion of the muscles on the back side of the knee? The diagnostic criteria are: 1 neither full extension nor full flexion of the knee (because of the bowstring action of the posterior knee muscles – the N cord muscles) 2 MRI showing extensive edema of the posterior group of muscles 3 physical examination of pressure points and muscle tension on the posterior side 4 laboratory tests for elevated CK (creatine kinase), CK-MB (creatine kinase isoenzyme) and even LDH (lactate dehydrogenase). The reason for this is that during travel, especially when going up and down hills, the knee joint is in light flexion, and the muscles on the back side of the knee joint cannot relax after a long time of maintaining this angle. In addition to rest, medications to relieve muscle spasm, such as cloxazolone and ethylprednisolone hydrochloride, should be given as treatment. In addition to rest, we should give drugs to relieve muscle spasm, such as clozoxazone and eperisone hydrochloride, anti-inflammatory and pain-relieving drugs, such as fenbid and fotarine, and herbal medicines to activate blood circulation and remove blood stasis, such as qilisan and yunnan baiyao, especially oral tonics, which can be very effective (two cases). Special experience – the relationship between patellofemoral arthritis and muscle spasm of the posterior group of the knee, these two lesions are mutually causal, patellofemoral arthritis can respond to pain in the posterior part of the knee, and muscle spasm of the posterior group of the knee can respond to pain in the anterior part of the knee.