Breaking the bones around the knee often involves the cartilage surface. Unless the bone fragments are in an anatomical position often surgical fixation is required. Joint stiffness and the development of post-traumatic arthritis later in life are possible complications.
A meniscal (cartilage) tear can cause acute pain, swelling and giving way sensations. It is usually the result of a twisting or deep knee bending injury but with advancing age it can happen spontaneously. Symptoms can improve for 3 months and if symptoms persist an arthroscopy (keyhole surgery) is an option.
The main tendons are the quadriceps and patella tendons. When they rupture surgical repair is required. The surgical repair needs to be protected with a cast or brace and full rehabilitation can take months.
A bursa is a lubricating structure between the skin and bone or tendon. There are several around the knee joint, mainly at the front. They can get inflamed or infected causing pain, redness and swelling. Bursitis can be caused by repeated kneeling (carpet fitters, roofers), a blow to the knee or a wound. Anti-inflammatory measures may help but if there is evidence of infection antiobiotics are needed. Sometimes the bursa needs to be drained surgically if it contains pus.
Dislocation of the knee cap (patella) is the most common injury. This can happen after a direct knock or after a twisting injury when the groove in which the patella runs is shallow (trochlea dysplasia). The dislocation can be reduced with the knee straight. Quadriceps muscle strengthening can help to prevent further dislocations but sometimes a ligament reconstruction is required to stabilise the patella.
Ligament sprain or tear
The main knee ligaments are the medial and lateral collateral (side) ligaments and the anterior and posterior cruciate (front and back) ligaments. A sprain is a partial tear which usually heals without problems. A full tear can cause instability of the joint and if high impact activities are performed a ligament reconstruction is an option.
A knee can swell up acutely and be very painful. This can be the result of inflammation (common), infection or bleeding into the joint (both rare). Acute inflammation can be related to arthritis (osteo or rheumatoid), gout or trauma. Rare causes are tumours and Pigmented Villo-Nodular Synovitis (PVNS). Draining the joint allows investigation of the fluid to find the cause.